Open Source Ecology - User contributions [en]

Germany/People

2015-10-25T02:24:31Z

Alex Shure: removed myself

{{Germany}}
=Attention! This wiki entry is deprecated. The content moved to [http://wiki.opensourceecology.de Open Source Ecology Germany].=

 
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We are developing OSE Germany:

* [[Andre Jonas]] (Kiel) – Translation and proofreading
* [[Andreas Gmeiner]] (Regensburg) – [[Germany/OSE_Community|OSE Community]], Ecology, Permaculture, 3D Printing
* [[Aron Homberg]] (München) - Small Oven, IT and more
* Hanspeter Maier (Mörfelden) - Lightweight Construction with Fiberglass(30 years experience), Heat Engineering, [[Germany/Wind_Turbine|Wind Turbine]]; MaierH (dot) P (at) t-online (dot) de
* Mabe, Mister Scr3wdriv3r (Freiburg) - [[CNC Circuit Mill]]
* [[Nikolay Georgiev]] (Darmstadt) – Communication and Organization, [[Germany/OSE_Community|OSE Community]], [[Germany/Wind_Turbine|Wind Turbine]], [[Germany/Distributive_Enterprise|Distributive Enterprise]]
* [[Paul Leidorf]] (Hamburg) - CAD, translation
* [[Tim-Rasmus_Kiehl|Rasmus Kiehl]] (Toronto, Canada) - [[biochar]], [[Medical_Swadeshi|medical swadeshi]], [[microfluidics|low-cost diagnostics]], [[Integrated_Food_and_Waste_Management_System|integrated farming]]
* [[Thomas von der Elbe]] (Dresden) - p2p-democracy, Organization, Education, Dokumentation

<html>
<iframe width="600" height="540" frameborder="0" scrolling="no" marginheight="0" marginwidth="0" src="http://maps.google.de/maps/ms?msa=0&msid=209565165832430470075.0004adf47cafeceb806f8&hl=en&ie=UTF8&t=h&ll=51.165567,10.063477&spn=7.443174,13.183594&z=6&output=embed"></iframe> View <a href="http://maps.google.de/maps/ms?msa=0&msid=209565165832430470075.0004adf47cafeceb806f8&hl=en&ie=UTF8&t=h&ll=51.165567,10.063477&spn=7.443174,13.183594&z=6&source=embed" style="color:#0000FF;text-align:left">OSE - Europe (official)</a> in a larger map
</html>

People who have helped us and are currently inactive:
* [[Jalil Wahdatehagh]] (Munich) – Media Design and Production

Note: we add people to the list only if they are: 1) already in contact with some people from the list and 2) contributing to the OSE development in Germany.

[[Category: OSE Germany]]

Talk:True Fans

2015-10-25T02:23:46Z

Alex Shure:

== Are there any left? ==

What are the current numbers of "True Fans"? The last update has been a long time ago. --[[User:Alex Shure|Alex Shure]] ([[User talk:Alex Shure|talk]]) 03:23, 25 October 2015 (CET)

Talk:True Fans

2015-10-25T02:23:35Z

Alex Shure: /* Are there any left? */ new section

== Are there any left? ==

What are the current numbers of "True Fans"? The last update has been a long time ago.

Alex Shure

2015-10-25T02:22:01Z

Alex Shure: Replaced content with "Deprecated"

Deprecated

Talk:Micro Power Cube

2014-03-25T14:07:58Z

Alex Shure: Created page with "This crude BOM lacks an energy source, an ESC and cooling. Needs more than $300 in batteries alone to be able to operate an hour at full power."

This crude BOM lacks an energy source, an ESC and cooling. Needs more than $300 in batteries alone to be able to operate an hour at full power.

Alex Shure

2014-03-25T13:55:46Z

Alex Shure: /* HOW can you help? */

{{InternalWikiCommunication|Alex_Shure}}
[[Image:Alex_Shure.jpg|thumb|Alex Shure]]

==Team Culturing Information==

==='''WHO''' are you?===
*''Name'' - Alex Shure
*''Location (country)'' - Germany
*''Contact Information (email, phone)'' - etemu.com at googlemail.com, mobile: +49 151 five two seven 16901
*''Introduction Video'' -
*''Resume/CV'' - technologist, inventor: electronics, prototyping, research and development.

==='''WHY''' are you motivated to support/develop this work?===
*''Do you support open source culture?''
''This question is pretty obsolete for any profile on this wiki.''

*''Why are you interested in collaborating with us?''
I like to create/craft/tinker.

*''What should happen so that you become more involved with OSE Europe?''
Let's wait for some time to pass, [[OSE_Europe/Germany|OSE Community in Germany]] is too virgin right now.
However, successful fundraising and a lab/workshop village/place full of interesting people, ideas and machines in Germany seem attractive to me.

*''What is missing in OSE Europe?''
- New inventions. We shouldn't focus on the [[GVCS]].

- An efficient electronic infrastructure, preferably low voltage DC.

- Also, the [[GVCS]] lacks some quite important everyday machines. For the average household, there are definitely some appliances missing: Washing machine, dish washer, cooking range/small oven, most importantly a refrigerator!

- Tools: Router, table saw, vacuum cleaner, chainsaw, ...

*''What are your suggestions for improvement in OSE Europe?''
(tbd)

==='''WHAT''' are your skills?===

*''List all of your skills in these areas, at what level (beginner, intermediate, advanced) and where did you practice them:''
**Humor - advanced, dark and filthy
**Natural Building - earthship design basics, geodesic structures
**Woodworking - intermediate. I worked as a carpenter some time ago. And I carved a spoon once.
**Electronics - advanced. I prefer SMD over THT. I own more dev kits than jackets. My DSO has 4 channels.
**Automation - intermediate. The light in my bathroom is automatically switched with a pyroelectric sensor.
**Engineering - advanced
**CAD Design - beginner
**Energy - advanced -> power sources, renewable energy, efficiency calculations, grid layout, power consumption, rectifying techniques, power supplies, inverters, off-grid-systems
**CNC - advanced -> construction, maintenance of stepping motor and servo driven machines, retrofitting lathes and milling machines with modern hardware, LinuxCNC (formerly EMC2, the enhanced machine controller)
**Product Design - advanced <-> working at etemu.com prototyping

*''How have you already contributed to OSE, OSE Europe and Open Source Hardware?''
I include the OSHW logo in any of my open source PCB and hardware designs.
I talk about it and work actively on projects like the [[Germany/Wind_Turbine]] or [[TiVA]]

===HOW can you help?===

*''How do you want to contribute?''
Giving advice in engineering and bringing new inventions to life. Creating [[OSE_Europe/Germany|OSE Community in Germany]] http://www.opensourceecology.de

*''Are you interested in building GVCS or other Open Source Hardware equipment in Europe? If so which ones?''
Yes.

*''Are you an OSE [[True Fans|True Fan]]?''
No.

[[Category:Team Culturing Europe]] [[Category:Profiles Germany]]

<references />

Germany/Get Involved

2013-05-21T14:48:15Z

Alex Shure:

{{Germany}}
=Attention! This wiki entry is deprecated. The content moved to [http://wiki.opensourceecology.de Open Source Ecology Germany].=

 
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We are an open network and everyone can participate. You can [[Germany/Communication#Google_Group|introduce yourself]] to the community and [[Germany/Profile|create a public profile]] of yours.

{{Germany_Get_Involved}}

[[Category: OSE Germany]]

Germany/IT Tasks

2013-05-21T14:48:00Z

Alex Shure:

{{Germany}}
=Attention! This wiki entry is deprecated. The content moved to [http://wiki.opensourceecology.de Open Source Ecology Germany].=

 
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We need on help on the following IT Tasks. Feel free to click on the items below to learn more. 
If you want to help please contact [[Nikolay]].

==Tasks==
===phpBB Forum===

Forum email notifications contain a link like this: 
http://forum.opensourceecology.de/viewtopic.php?f=10&t=14&p=57&e=57 
which requires login to view the link. The problem is the "p" and "e" parameter. To view the thread without login, the link should be like that: 
http://forum.opensourceecology.de/viewtopic.php?f=10&t=14#p57 
TODO: Transform the link as described above. 
Status: the task is open for contribution. Please contact [[Nikolay]] for more information.

<html>
<iframe src="https://trello.com/board/ose-europe-it/4f46f7bef7aabce304a93a31" style="width: 95%; height: 400px"></iframe>
</html>

[[Category: OSE Germany]]

Germany/OSE Village

2013-05-21T14:46:43Z

Alex Shure:

{{Germany}}
=Attention! This wiki entry is deprecated. The content moved to [http://wiki.opensourceecology.de Open Source Ecology Germany].=

 
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==Introduction==
Paradigms are shifting and new practical solutions are needed. This year we want to start an Open Source Ecology (OSE) community in Germany and we are looking for a Dedicated Team to make this happen.

The people involved in the project will be sharing openly and for free economically significant information. We want to open source the ecology of the environmental, societal and technological systems so that we contribute directly to the creation of an open source economy – an economy that optimizes both production and distribution, while providing environmental regeneration and social justice.

We start with the technology needed for the creation of a small scale civilization with modern comforts – the Global Village Construction Set and other relevant tools. From tractors, wind turbines to cars. Every technology will be developed with values like modularity, simplicity, lifetime design, low-cost, closed loop manufacturing, Do-It-Yourself, flexible fabrication and high performance. We want to open source the whole lifecycle of each technology – from its parts sourcing, fabrication, use, maintain and repair to its reuse and recycle. We will open source also our ecological food production, housing, workshop constructions and business models – our complete economy. All this economically signicant information will be saved digitally on the Internet as text, manufacturing files, pictures and videos so that we distribute it not only to our current generation, but to all other future generations on Earth – who can use it and build upon it! We are looking for the pioneers to join us in this endeavor!

Our first main goal is to establish the initial Development Team dedicated to create the community in 2012. The Development Team is open to everyone who works on the creation of the community and has a specific group of people, the Core Team, who will start up and develop the community no matter where or how. We would need help with all areas of community creation and development: organization, communication, land search, ecological housing and workshop architecture and construction, fabrication, engineering, mechatronics, permaculture and organic farming, business, law, social, financial etc.

We have laid out an initial Roadmap. In January we will connect with a lot of people and learn about each other and the possibilities to start the community. Visits are planned in Frankfurt and Berlin. The Roadmap will be expanded and become more concrete as we grow.

Why Germany? The people in Germany can and will play a vital role in the OSE development in Europe and the world. In Germany there are very good engineers, most people are well financially and here is one of the best sustainability and open source cultures in the world. It is a perfect place to start an OSE community.

==Status==
searching for people and place.

==Roadmap==

<html>
<iframe src="https://trello.com/board/ose-community-germany/4f6d988b603566786805b1c7" style="width: 90%; height: 400px"></iframe>
</html>

==People==
People engaged in the creation of the OSE Community:

* [[Alex Shure]] – technical advice, prototyping
* [[Andreas Gmeiner]] - permaculture, fabrication
* Hermann - electrical engineering, industrial design
* [[Nikolay Georgiev]] - communication and organization, basic fabrication skills

==Place==
We are looking for an '''existing community''' or a '''small town''' that:
* is already living to some degree sustainably and
* is open and willing to vitalize the local and global economy by engaging in open source hardware development.

If you know such communities or small towns, please contact us.

===Suggested Places===

* http://www.ttwitzenhausen.de/ [http://g.co/maps/kgebg Google Map] TT, CSA, GNE, Uni for Eco Agriculture, Open Uni for Ecovillage Design,... (connection: Daniel)
* http://kesselberg.info/ - [http://g.co/maps/8bxuk Google Map], not checked. (connection: Dante)
* CSA in Wendland / Altmark - together with Dorfprojekt. (connection: Urs)
* Wendland (connection: Marc)
** http://www.werkhof-kukate.de/ - Around 40 people can live and work here
** terra preta agriculture - http://www.cicero.de/kapital/%C3%B6kologischer-anbau-bernstorff-wendepunktzukunft-methoden-indios/46580?seite=2
** http://www.akademie-ee.de/ - academy for renewable energies
** http://www.emma-ev.de/ - agency for renewable energies
** region of bio-energy - http://www.bioenergie-region-we.de/bioenergiedorf.html
** one of the biggest and most experienced companies for power-engines and systems based on bio-gas in the region - http://www.dreyer-bosse.de/
** Grüne Werkstatt - http://www.mediafire.com/?ncn83fn369sd7q1
** http://www.altmark.eu/
* http://www.wukania.net/ - workshop available, possibility to develop machines. Nikolay talked on the phone with Paul.
* Nordbayern - http://oseeurope.org/forum/viewtopic.php?f=22&t=126
* [https://maps.google.com/maps?q=Weickersdorf,+Bischofswerda,+Deutschland&hl=en&sll=52.045734,12.974854&sspn=5.791845,10.799561&oq=Weickersdorf,+Bischofswerda&t=h&hnear=Weickersdorf,+Saxony,+Germany&z=15 Weickersdorf] - we have 4 and a half acres and a huge barn for building and assembly of existing ideas or proto types. We would like to offer the use of our land barn plus accomodation to the team for 2 to 3 years in return for something to power the house and barn and finally get off the grid. [https://skydrive.live.com/?cid=2bd1734986b12da3&Bsrc=SkyMail&Bpub=SDX.SkyDrive&sc=Photos&resid=2BD1734986B12DA3!350&id=2BD1734986B12DA3!350 See photos], Contacts (Kamala) are in the [https://groups.google.com/forum/?fromgroups#!topic/ose-europe/wCXkTfPrfYs Google Group].
* http://kombinatg.org/ - Stefan Raabe. [https://maps.google.com/maps?q=Gatschow+22+D-17111+Beggerow&hl=en&geocode=+&hnear=Gatschow+22,+Gatschow+17111+Beggerow,+Mecklenburg-Vorpommern,+Germany&t=h&z=16 Google Map in Gatschow].
* http://www.coolmuehle.org/ - (connection: Simon)
* Karlshof PAG? - noch kein Kontakt
* http://www.bioenergiedorf.de/con/cms/front_content.php?idcat=253 not contacted yet.

==Contact==
If you want to get involved in the OSE Community please contact [[Nikolay]].

[[Category: OSE Germany]]

Germany/People

2013-05-21T14:44:42Z

Alex Shure:

{{Germany}}
=Attention! This wiki entry is deprecated. The content moved to [http://wiki.opensourceecology.de Open Source Ecology Germany].=

 
----
 
----
 
----
We are developing OSE Germany:

* [[Alex Shure]] (Berlin) – Technical advice, prototyping, proofreading, [[Germany/Wind_Turbine|Wind Turbine]], [[TiVA]], [[Germany/OSE_Community|OSE Community]]
* [[Andre Jonas]] (Kiel) – Translation and proofreading
* [[Andreas Gmeiner]] (Regensburg) – [[Germany/OSE_Community|OSE Community]], Ecology, Permaculture, 3D Printing
* [[Aron Homberg]] (München) - Small Oven, IT and more
* Hanspeter Maier (Mörfelden) - Lightweight Construction with Fiberglass(30 years experience), Heat Engineering, [[Germany/Wind_Turbine|Wind Turbine]]; MaierH (dot) P (at) t-online (dot) de
* Mabe, Mister Scr3wdriv3r (Freiburg) - [[CNC Circuit Mill]]
* [[Nikolay Georgiev]] (Darmstadt) – Communication and Organization, [[Germany/OSE_Community|OSE Community]], [[Germany/Wind_Turbine|Wind Turbine]], [[Germany/Distributive_Enterprise|Distributive Enterprise]]
* [[Paul Leidorf]] (Hamburg) - CAD, translation
* [[Tim-Rasmus_Kiehl|Rasmus Kiehl]] (Toronto, Canada) - [[biochar]], [[Medical_Swadeshi|medical swadeshi]], [[microfluidics|low-cost diagnostics]], [[Integrated_Food_and_Waste_Management_System|integrated farming]]
* [[Thomas von der Elbe]] (Dresden) - p2p-democracy, Organization, Education, Dokumentation

<html>
<iframe width="600" height="540" frameborder="0" scrolling="no" marginheight="0" marginwidth="0" src="http://maps.google.de/maps/ms?msa=0&msid=209565165832430470075.0004adf47cafeceb806f8&hl=en&ie=UTF8&t=h&ll=51.165567,10.063477&spn=7.443174,13.183594&z=6&output=embed"></iframe> View <a href="http://maps.google.de/maps/ms?msa=0&msid=209565165832430470075.0004adf47cafeceb806f8&hl=en&ie=UTF8&t=h&ll=51.165567,10.063477&spn=7.443174,13.183594&z=6&source=embed" style="color:#0000FF;text-align:left">OSE - Europe (official)</a> in a larger map
</html>

People who have helped us and are currently inactive:
* [[Jalil Wahdatehagh]] (Munich) – Media Design and Production

Note: we add people to the list only if they are: 1) already in contact with some people from the list and 2) contributing to the OSE development in Germany.

[[Category: OSE Germany]]

Germany/Roadmap

2013-05-21T14:44:30Z

Alex Shure:

{{Germany}}

=Attention! This wiki entry is deprecated. The content moved to [http://wiki.opensourceecology.de Open Source Ecology Germany].=

 
----
 
----
 
----

This is the Roadmap of the development of OSE Germany in general. If you want to see the roadmaps of the concrete projects, visit the [[Germany/Projects|project pages]].

==Current Work==
You can see the ongoing tasks here: https://trello.com/board/ose-germany/4f5f9e3194ba5ea81c363e99

To contribute, choose a task from the "To Do" list and send email that you are working on it in the [https://groups.google.com/forum/#!forum/ose-germany Google Group].

<html>
<iframe src="https://trello.com/board/ose-germany/4f5f9e3194ba5ea81c363e99" style="width: 95%; height: 600px"></iframe>
</html>

==Past==

===February 2012===
*February 2 - Nikolay will speak with Katharina Weber on the project - [[OSE_Europe/Germany/Projects#How_to_build_a_Strawbale_House|open sourcing "How to build a strawbale house"]].
*February 4 - Nikolay goes to Berlin for about 2 weeks.
*February 5 - Meeting in Berlin planned with other organizations. More info soon.
*February 11 - Start of "Open Agile SCRUM GVCS machine development" mailing list - We begin to discuss the OSE:E project of constructing a wind turbine
*February 22 - First online meeting on the OSE:E project "VAWT"

===January 2012===
*January 5 - [[Image:check.png]] contact 20 Hackerspaces (around Munich, Stuttgart/KA, Frankfurt, Aachen).
*January 11 - [[Image:check.png]] Vortrag in Darmstadt, [http://maps.google.com/maps?q=darmstadt,+Wilhelm-Leuschner-Strasse+36&hl=en&ie=UTF8&sll=37.0625,-95.677068&sspn=52.815565,114.169922&vpsrc=0&hnear=Wilhelm-Leuschner-Stra%C3%9Fe+36,+64293+Darmstadt,+Hessen,+Germany&t=h&z=16 Trollhöhle], mit [http://chaos-darmstadt.de/cda Chaos Darmstadt], 20:00.
*January 12 - [[Image:check.png]] Radio interivew on [http://c-radar.de/ C-Radar], Darmstadt, 21:00.
*January 13-15 - [[Image:check.png]] in Leipzig, speak at [http://acampadaleipzig.org/blog/ Occupy Leipzig], speak with people interested in OSE.
*January 20-22 - [[Image:check.png]] in Bittelbronn, south of Stuttgart, [http://www.thinkcamp.eu/wiki/pages/viewpage.action?pageId=5669569 IdeenCamp], on OSE, [http://www.dorfwiki.org/wiki.cgi?VillageInnovationTalk Village Innovation Talk] with [[Franz Nahrada]] and others.
*January 25 - Design a flyer for OSE Germany
*January 31 - [[Image:check.png]] Visit Berlin, meeting in Open Design City is planned, connecting with people to discuss rural and urban OSE developments in/around Berlin.
*January 31 - Translate [[Global Village Construction Set/de]]
*January 31 - Translate the OSE Paradigm in German http://sync.in/bNULbH0F0R

[[Category: OSE Germany]]

Germany/Roadmap

2013-05-21T14:43:58Z

Alex Shure:

{{Germany}}

=Attention! This wiki entry is deprecated. The content moved to [http://wiki.opensourceecology.de Open Source Ecology Germany].=

----

----

----

This is the Roadmap of the development of OSE Germany in general. If you want to see the roadmaps of the concrete projects, visit the [[Germany/Projects|project pages]].

==Current Work==
You can see the ongoing tasks here: https://trello.com/board/ose-germany/4f5f9e3194ba5ea81c363e99

To contribute, choose a task from the "To Do" list and send email that you are working on it in the [https://groups.google.com/forum/#!forum/ose-germany Google Group].

<html>
<iframe src="https://trello.com/board/ose-germany/4f5f9e3194ba5ea81c363e99" style="width: 95%; height: 600px"></iframe>
</html>

==Past==

===February 2012===
*February 2 - Nikolay will speak with Katharina Weber on the project - [[OSE_Europe/Germany/Projects#How_to_build_a_Strawbale_House|open sourcing "How to build a strawbale house"]].
*February 4 - Nikolay goes to Berlin for about 2 weeks.
*February 5 - Meeting in Berlin planned with other organizations. More info soon.
*February 11 - Start of "Open Agile SCRUM GVCS machine development" mailing list - We begin to discuss the OSE:E project of constructing a wind turbine
*February 22 - First online meeting on the OSE:E project "VAWT"

===January 2012===
*January 5 - [[Image:check.png]] contact 20 Hackerspaces (around Munich, Stuttgart/KA, Frankfurt, Aachen).
*January 11 - [[Image:check.png]] Vortrag in Darmstadt, [http://maps.google.com/maps?q=darmstadt,+Wilhelm-Leuschner-Strasse+36&hl=en&ie=UTF8&sll=37.0625,-95.677068&sspn=52.815565,114.169922&vpsrc=0&hnear=Wilhelm-Leuschner-Stra%C3%9Fe+36,+64293+Darmstadt,+Hessen,+Germany&t=h&z=16 Trollhöhle], mit [http://chaos-darmstadt.de/cda Chaos Darmstadt], 20:00.
*January 12 - [[Image:check.png]] Radio interivew on [http://c-radar.de/ C-Radar], Darmstadt, 21:00.
*January 13-15 - [[Image:check.png]] in Leipzig, speak at [http://acampadaleipzig.org/blog/ Occupy Leipzig], speak with people interested in OSE.
*January 20-22 - [[Image:check.png]] in Bittelbronn, south of Stuttgart, [http://www.thinkcamp.eu/wiki/pages/viewpage.action?pageId=5669569 IdeenCamp], on OSE, [http://www.dorfwiki.org/wiki.cgi?VillageInnovationTalk Village Innovation Talk] with [[Franz Nahrada]] and others.
*January 25 - Design a flyer for OSE Germany
*January 31 - [[Image:check.png]] Visit Berlin, meeting in Open Design City is planned, connecting with people to discuss rural and urban OSE developments in/around Berlin.
*January 31 - Translate [[Global Village Construction Set/de]]
*January 31 - Translate the OSE Paradigm in German http://sync.in/bNULbH0F0R

[[Category: OSE Germany]]

Germany/Roadmap

2013-05-21T14:43:16Z

Alex Shure: /* Content moved to Open Source Ecology Germany. */

{{Germany}}

=Attention! This wiki entry is deprecated. The content moved to [http://wiki.opensourceecology.de Open Source Ecology Germany].=

This is the Roadmap of the development of OSE Germany in general. If you want to see the roadmaps of the concrete projects, visit the [[Germany/Projects|project pages]].

==Current Work==
You can see the ongoing tasks here: https://trello.com/board/ose-germany/4f5f9e3194ba5ea81c363e99

To contribute, choose a task from the "To Do" list and send email that you are working on it in the [https://groups.google.com/forum/#!forum/ose-germany Google Group].

<html>
<iframe src="https://trello.com/board/ose-germany/4f5f9e3194ba5ea81c363e99" style="width: 95%; height: 600px"></iframe>
</html>

==Past==

===February 2012===
*February 2 - Nikolay will speak with Katharina Weber on the project - [[OSE_Europe/Germany/Projects#How_to_build_a_Strawbale_House|open sourcing "How to build a strawbale house"]].
*February 4 - Nikolay goes to Berlin for about 2 weeks.
*February 5 - Meeting in Berlin planned with other organizations. More info soon.
*February 11 - Start of "Open Agile SCRUM GVCS machine development" mailing list - We begin to discuss the OSE:E project of constructing a wind turbine
*February 22 - First online meeting on the OSE:E project "VAWT"

===January 2012===
*January 5 - [[Image:check.png]] contact 20 Hackerspaces (around Munich, Stuttgart/KA, Frankfurt, Aachen).
*January 11 - [[Image:check.png]] Vortrag in Darmstadt, [http://maps.google.com/maps?q=darmstadt,+Wilhelm-Leuschner-Strasse+36&hl=en&ie=UTF8&sll=37.0625,-95.677068&sspn=52.815565,114.169922&vpsrc=0&hnear=Wilhelm-Leuschner-Stra%C3%9Fe+36,+64293+Darmstadt,+Hessen,+Germany&t=h&z=16 Trollhöhle], mit [http://chaos-darmstadt.de/cda Chaos Darmstadt], 20:00.
*January 12 - [[Image:check.png]] Radio interivew on [http://c-radar.de/ C-Radar], Darmstadt, 21:00.
*January 13-15 - [[Image:check.png]] in Leipzig, speak at [http://acampadaleipzig.org/blog/ Occupy Leipzig], speak with people interested in OSE.
*January 20-22 - [[Image:check.png]] in Bittelbronn, south of Stuttgart, [http://www.thinkcamp.eu/wiki/pages/viewpage.action?pageId=5669569 IdeenCamp], on OSE, [http://www.dorfwiki.org/wiki.cgi?VillageInnovationTalk Village Innovation Talk] with [[Franz Nahrada]] and others.
*January 25 - Design a flyer for OSE Germany
*January 31 - [[Image:check.png]] Visit Berlin, meeting in Open Design City is planned, connecting with people to discuss rural and urban OSE developments in/around Berlin.
*January 31 - Translate [[Global Village Construction Set/de]]
*January 31 - Translate the OSE Paradigm in German http://sync.in/bNULbH0F0R

[[Category: OSE Germany]]

Germany/Roadmap

2013-05-21T14:42:33Z

Alex Shure:

{{Germany}}

=Content moved to [http://wiki.opensourceecology.de Open Source Ecology Germany].=

This is the Roadmap of the development of OSE Germany in general. If you want to see the roadmaps of the concrete projects, visit the [[Germany/Projects|project pages]].

==Current Work==
You can see the ongoing tasks here: https://trello.com/board/ose-germany/4f5f9e3194ba5ea81c363e99

To contribute, choose a task from the "To Do" list and send email that you are working on it in the [https://groups.google.com/forum/#!forum/ose-germany Google Group].

<html>
<iframe src="https://trello.com/board/ose-germany/4f5f9e3194ba5ea81c363e99" style="width: 95%; height: 600px"></iframe>
</html>

==Past==

===February 2012===
*February 2 - Nikolay will speak with Katharina Weber on the project - [[OSE_Europe/Germany/Projects#How_to_build_a_Strawbale_House|open sourcing "How to build a strawbale house"]].
*February 4 - Nikolay goes to Berlin for about 2 weeks.
*February 5 - Meeting in Berlin planned with other organizations. More info soon.
*February 11 - Start of "Open Agile SCRUM GVCS machine development" mailing list - We begin to discuss the OSE:E project of constructing a wind turbine
*February 22 - First online meeting on the OSE:E project "VAWT"

===January 2012===
*January 5 - [[Image:check.png]] contact 20 Hackerspaces (around Munich, Stuttgart/KA, Frankfurt, Aachen).
*January 11 - [[Image:check.png]] Vortrag in Darmstadt, [http://maps.google.com/maps?q=darmstadt,+Wilhelm-Leuschner-Strasse+36&hl=en&ie=UTF8&sll=37.0625,-95.677068&sspn=52.815565,114.169922&vpsrc=0&hnear=Wilhelm-Leuschner-Stra%C3%9Fe+36,+64293+Darmstadt,+Hessen,+Germany&t=h&z=16 Trollhöhle], mit [http://chaos-darmstadt.de/cda Chaos Darmstadt], 20:00.
*January 12 - [[Image:check.png]] Radio interivew on [http://c-radar.de/ C-Radar], Darmstadt, 21:00.
*January 13-15 - [[Image:check.png]] in Leipzig, speak at [http://acampadaleipzig.org/blog/ Occupy Leipzig], speak with people interested in OSE.
*January 20-22 - [[Image:check.png]] in Bittelbronn, south of Stuttgart, [http://www.thinkcamp.eu/wiki/pages/viewpage.action?pageId=5669569 IdeenCamp], on OSE, [http://www.dorfwiki.org/wiki.cgi?VillageInnovationTalk Village Innovation Talk] with [[Franz Nahrada]] and others.
*January 25 - Design a flyer for OSE Germany
*January 31 - [[Image:check.png]] Visit Berlin, meeting in Open Design City is planned, connecting with people to discuss rural and urban OSE developments in/around Berlin.
*January 31 - Translate [[Global Village Construction Set/de]]
*January 31 - Translate the OSE Paradigm in German http://sync.in/bNULbH0F0R

[[Category: OSE Germany]]

Talk:Universal Power Supply

2013-04-14T00:17:10Z

Alex Shure:

"Rectifyers can be either passive schottky diode bridges, or active (IC-controlled) MOSFET H-bridges. Passive ones are cheaper, and ultimately more efficient for very high currents, while active ones are superior for low-medium-and-maybe-high currents yet more expensive. This design choice affects price, producability and simplicity."

This statement and the corresponding graph need better research. E.g. full-bridge Schottky diode rectifiers have a Vf_drop of at least 2*1V at high currents like those shown in the graph.

It should be noted that hard switched MOSFETS can be paralelled (and often are) without risk of thermal runaway because on resistance increases with temperature, so the active synchronous rectification option is scalable in ways that the passive diodes just aren't because their conduction voltage reduces with temperature. In addition, all MOSFETS are also Diodes, so when the are turned on in rectification mode (reverse conduction) you get the MOSFET 1mOhm characteristic in paralell with a high current, usualy low forward voltage diode with no extra expense giving the best of both worlds.--[[User:Alex Shure|Alex Shure]] ([[User talk:Alex Shure|talk]]) 02:17, 14 April 2013 (CEST)

== General purpose or specific? ==

'A large range of power electronic devices is desirable within the infrastructure of communities. Having an individual power supply for each is redundant and expensive. A modular UPS construction kit is desirable as an analogue to the 'industrial-strength Lego' that we have already demonstrated for heavy mechanical hardware infrastructures.'

The list of different power uses and voltages for the Universal Power Supply begs a few questions. The standard AC supply system means that every device has its own unique custom power supply built in (or supplied with the device on a wire) that someone has spent a lot of time designing to be perfect for that device. starting from (eg) 12Vdc using the same electronics for supplying 19Vdc to a laptop (10A inductor, basic boost topology with syncronous MOSFET rectification, must maintain 19V at all times +-0.2V) as for supplying 19Vdc for a MIG welder (MIG welder likes variable voltage up to 39V and current sensitive drop in output voltage helps the arc to stabilise, could be done with 1:1:1:1 autotransformer in push-pull followed by inductor - all rated for 200A output operation, up to 600A input) doesn't make much sense, and what about when people want to do both at the same time? I know what is meant by 'redundant and expensive' but actualy, redundancy can be of great benefit when things fail, and even when they don't too. eg: we have 3 DC-AC inverters. 400W, 1000W, 3000W rated. we currently have bothe the 400W and the 3000W permanently installed, because the 3000W inverter (used for washing machine and electric chainsaw mostly) consumes 3A just to run its transformers, whereas the 400W one only needs 200mA for itself and someone needs to run their laptop for 5H a day (too far away for a 12V feed) because they're writing a book. The 3000W got blown by a close lightning strike and the only just superceded 1000W inverter came back to run the washing machine while I repaired the 3000W one. When the sky is too dark for a few days we revert to using direct DC-DC laptop chargers to reduce the load even further. In short, I cannot imagine a one-size-fits-all machine in this category. Please convince me.

==in my opinion==
I agree that a one-size fits all is not feasibly acheived. I think based on the ecology model though, they are looking for a heavy load inverter that could handle multiple inputs and outputs; akin to a whole house inverter system you might find at solar stores or RV suppliers would be my guess. My main question is: why not call it by its most common/accepted name? Its not an Universal Power Supply.. Its an Uninterruptable Power Supply. Its main purpose is to keep supplying electricity when main systems (electric company or whatnot) fail. Thats my main suggest.. call it by its proper name, and you'll likely see more hits and possibly more help with the project.

OSE Governance

2013-04-05T18:53:53Z

Alex Shure:

{{Organization}}

'''[[OSE]]''' is currently run as a dictatorship solely under the direction of [[Marcin Jakubowski]].

There are forks of OSE which encourage the true ''Open'' Source philosophy and have a democratic hierarchy, like

'''OSEG''' - Open Source Ecology Germany[[http://www.OpenSourceEcology.de]]

'''OSEE''' - Open Source Ecology Europe[[http://oseeurope.org]]

'''OTF''' - Open Tech Forever[[http://www.opentechforever.com]]

Talk:Jeff Moe

2013-04-03T21:43:06Z

Alex Shure: Created page with "Was that an interview? Could you please format it accordingly. Thanks --~~~~"

Was that an interview? Could you please format it accordingly. Thanks --[[User:Alex Shure|Alex Shure]] ([[User talk:Alex Shure|talk]]) 23:43, 3 April 2013 (CEST)

OSE Governance

2013-04-03T12:52:45Z

Alex Shure:

{{Organization}}

'''[[OSE]]''' is currently run as a dictatorship solely under the direction of [[Marcin Jakubowski]].

Other forms of governance will be explored here.
* [[OSE Governance/Advisors|Advisors]]
* [[OSE Governance/Executive Director|Executive Director]]

Critics

2013-04-02T18:12:19Z

Alex Shure: Created page with "Apart from the well documented positive criticism OSE gets (TED, True Fans, ...) we hereby want to give negative critics a chance to be heard. Some of them seem very construct..."

Apart from the well documented positive criticism OSE gets (TED, True Fans, ...) we hereby want to give negative critics a chance to be heard. Some of them seem very constructive and might help us and OSE as an organisation to become better:

<blockquote>It is worth noting that '''OSE is hierarchically structured''' and that direct '''democracy is completely absent''' from its values. Folks should push for a democratized OSE/FeF giving participants democratic
control over the group.<ref>Marcus, March 8. 2013 http://forum.opensourceecology.org/discussion/1004/why-is-ose-so-quiet-lately </ref> </blockquote>

<blockquote>There were developers who left because there is no profit sharing for development work and labour when stuff got sold.
ie, you put a lot of time and effort improving the GVCS, and the piece gets sold, you get zilch of the net after material expenses. All went to OSE/Marcin.<ref>eBell, http://forum.opensourceecology.org/discussion/1004/why-is-ose-so-quiet-lately</ref> </blockquote>

<blockquote>All I see lately is voting to win money, etc. I understand the crowd funding thing didn't take off as envisioned. So no more bi-weekly ose mail? no updates anywhere (meaningful updates)<ref> Qdelima, http://forum.opensourceecology.org/discussion/1004/why-is-ose-so-quiet-lately </ref> </blockquote>

<blockquote>(...) there have been "ragequits" all the time over several years. Note how Yoonseo said he left also due in part by certain behaviour and comments by Marcin<ref>Marcin is the founder and self proclaimed leader of OSE</ref>.<ref>Beluga, March 15. 2013, http://forum.opensourceecology.org/discussion/1004/why-is-ose-so-quiet-lately</ref> </blockquote>
 
*Statement from Brianna, who was on site developing and fabricating GVCS products for 5 months as stated on http://forum.opensourceecology.org/discussion/comment/5310#Comment_5310:

----

As for me, I left for a few reasons.

(1.) '''Money'''. I was working out there for $10 per hour. Very small for the type of work I was doing- design and fabrication of the ironworker. I saw Marcin unwilling to pay even the most skilled labor more than $2k per month. If you aren't even willing to pay that, how on earth can you expect any quality results? At best you will be getting college students, like me, wanting to contribute, who don't have the skills to make a quality product. Or, you will be getting people doing it as a side thing, guaranteeing no results. I saw the bank accounts, and knew the organization had more than $400k in the bank. As a result, there was nobody there designing the machines. I didn't feel qualified to be designing this stuff. I felt like there should have been experts out there designing it so I could built it. There was nobody. I felt like I was defrauding the investors.

(2.) '''Lies about the quality of the products.''' The brick press produced shit for bricks. They didn't have one flat surface on them. I personally built 4 of these, which were all shipped out without proper testing. One was shipped out a year after it was supposed to be. The power cube worked for a week AT THE LONGEST.

(3.) '''Unsafe living conditions''' and insufficient infrastructure- when I was there, the well water was contaminated, and Marcin refused to fix it. There was literally algae the water tanks, and he was doing nothing to fix it. We had to either buy all water at the store, or drink from the RO system, which I had to personally install. The RO hardly produced 1/2 gallon per day to be spent among 15+ people because of the low pressure coming from the pump at the well. The well was also not producing enough to accomodate all the people there, so we could only use toilets to poop, and had to have VERY short showers.

(4.) Everyone I talked to who was working there had told me, independently, that they had felt "decieved" at their recruitment. That '''they had been lied to to get to come out there'''.
</blockquote>

----
 
*The CAD drawings seem to be inconsistent and lacking quality: http://forum.opensourceecology.org/discussion/915/ceb-press-iv
 
<references />

Germany/TiVA

2012-12-04T11:06:48Z

Alex Shure: Replaced content with "=Content moved to [http://wiki.opensourceecology.de/wiki/TiVA Open Source Ecology Germany].= ==Introduction== Part of the modular wind turbine syste..."

=Content moved to [http://wiki.opensourceecology.de/wiki/TiVA Open Source Ecology Germany].=

==Introduction==
Part of the modular [[Germany/Wind_Turbine|wind turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

[[Category: Wind energy]]

<references />

Germany/Wind Turbine

2012-12-04T11:05:41Z

Alex Shure:

{{Germany}}

=Content moved to [http://wiki.opensourceecology.de/wiki/Wind_Turbine/en Open Source Ecology Germany].=

==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.
[[File:Etemu.com_TiVA_l2_front_wip.jpg|720px|thumb|center|3D Model of a [[TiVA]] rotor, work in progress. Note the hollow wings, this is a hybrid lift/drag wing profile with a full load TSR<ref>Tip Speed Ratio</ref> of 0.85.]]

==Sources==
<references />

[[Category: Wind energy]]

Germany/Wind Turbine

2012-05-31T20:50:20Z

Alex Shure:

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.
[[File:Etemu.com_TiVA_l2_front_wip.jpg|720px|thumb|center|3D Model of a [[TiVA]] rotor, work in progress. Note the hollow wings, this is a hybrid lift/drag wing profile with a full load TSR<ref>Tip Speed Ratio</ref> of 0.85.]]

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA-NC)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
[[File:DSC08567_edit_tiva_session.jpg|512px|thumb|right|3D modelling session for [[TiVA]] with [[Alex Shure]] and Mario.]]
If you want to participate, just get in touch at our [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – lead designer, research and development, modeling, prototyping
* Mario - 3D modelling
* Achmed - 3D modelling, simulation with OpenFOAM
* [[chrono]] (is currently not available)
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to donate any material or machine which could come in handy for us.

==Roadmap / Log==

[[File:TiVA_2_1_lenz2_sim_safety_extreme.png|512px|thumb|right|Safety factor at an extreme gust of wind for a Lenz2 wing coupled to a rotor base with an aluminum arm. WIP<ref>work in progress</ref>]]

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.
* 20120512 [[Alex Shure]] 3D modelling session with Mario, finished [[TiVA]]'s rotor base and began with the Lenz2 lift/drag hybrid wing profile.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1, i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: Wind energy]]

Germany/Wind Turbine

2012-05-29T00:22:41Z

Alex Shure: /* Status */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.
[[File:Etemu.com_TiVA_l2_front_wip.jpg|720px|thumb|center|3D Model of a [[TiVA]] rotor, work in progress. Note the hollow wings, this is a hybrid lift/drag wing profile with a full load TSR<ref>Tip Speed Ratio</ref> of 0.85.]]

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
[[File:DSC08567_edit_tiva_session.jpg|512px|thumb|right|3D modelling session for [[TiVA]] with [[Alex Shure]] and Mario.]]
If you want to participate, just get in touch at our [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – lead designer, research and development, modeling, prototyping
* Mario - 3D modelling
* Achmed - 3D modelling, simulation with OpenFOAM
* [[chrono]] (is currently not available)
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to donate any material or machine which could come in handy for us.

==Roadmap / Log==

[[File:TiVA_2_1_lenz2_sim_safety_extreme.png|512px|thumb|right|Safety factor at an extreme gust of wind for a Lenz2 wing coupled to a rotor base with an aluminum arm. WIP<ref>work in progress</ref>]]

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.
* 20120512 [[Alex Shure]] 3D modelling session with Mario, finished [[TiVA]]'s rotor base and began with the Lenz2 lift/drag hybrid wing profile.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1, i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: Wind energy]]

File:Etemu.com TiVA l2 front wip.jpg

2012-05-29T00:18:01Z

Alex Shure:

Template:Cleanup-rewrite

2012-05-20T18:31:41Z

Alex Shure: Created page with "{{Ambox | type = content | image = 40x40px | text = This {{#ifeq:{{{section|}}}|yes|section|{{{2|article}}}}} '''may need to be rewritten ..."

{{Ambox
| type = content
| image = [[File:Crystal_Clear_app_kedit..png|40x40px]]
| text = This {{#ifeq:{{{section|}}}|yes|section|{{{2|article}}}}} '''may need to be rewritten entirely to comply with the Wiki's quality standards'''{{#if:{{{1|}}}|, as {{{1}}}}}. [{{fullurl:{{FULLPAGENAME}}|action=edit}} You can help]. The [[{{TALKPAGENAME}}|discussion page]] may contain suggestions.
| date = {{{date|}}}
}}

File:Crystal Clear app kedit..png

2012-05-20T18:28:34Z

Alex Shure:

Germany/Wind Turbine

2012-05-17T16:11:54Z

Alex Shure: /* Roadmap / Log */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
[[File:DSC08567_edit_tiva_session.jpg|512px|thumb|right|3D modelling session for [[TiVA]] with [[Alex Shure]] and Mario.]]
If you want to participate, just get in touch at our [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – lead designer, research and development, modeling, prototyping
* Mario - 3D modelling
* Achmed - 3D modelling, simulation with OpenFOAM
* [[chrono]] (is currently not available)
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to donate any material or machine which could come in handy for us.

==Roadmap / Log==

[[File:TiVA_2_1_lenz2_sim_safety_extreme.png|512px|thumb|right|Safety factor at an extreme gust of wind for a Lenz2 wing coupled to a rotor base with an aluminum arm. WIP<ref>work in progress</ref>]]

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.
* 20120512 [[Alex Shure]] 3D modelling session with Mario, finished [[TiVA]]'s rotor base and began with the Lenz2 lift/drag hybrid wing profile.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1, i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: Wind energy]]

File:TiVA 2 1 lenz2 sim safety extreme.png

2012-05-17T16:05:23Z

Alex Shure:

Alex Shure

2012-05-14T22:45:31Z

Alex Shure: /* HOW can you help? */

{{InternalWikiCommunication|Alex_Shure}}
[[Image:Alex_Shure.jpg|thumb|Alex Shure]]

==Team Culturing Information==

==='''WHO''' are you?===
*''Name'' - Alex Shure
*''Location (country)'' - Germany
*''Contact Information (email, phone)'' - etemu.com at googlemail.com, mobile: +49 151 five two seven 16901
*''Introduction Video'' -
*''Resume/CV'' - technologist, inventor: electronics, prototyping, research and development.

==='''WHY''' are you motivated to support/develop this work?===
*''Do you support open source culture?''
''This question is pretty obsolete for any profile on this wiki.''

*''Why are you interested in collaborating with us?''
I like to create/craft/tinker.

*''What should happen so that you become more involved with OSE Europe?''
Let's wait for some time to pass, [[OSE_Europe/Germany|OSE Community in Germany]] is too virgin right now.
However, successful fundraising and a lab/workshop village/place full of interesting people, ideas and machines in Germany seem attractive to me.

*''What is missing in OSE Europe?''
- New inventions. We shouldn't focus on the [[GVCS]].

- An efficient electronic infrastructure, preferably low voltage DC.

- Also, the [[GVCS]] lacks some quite important everyday machines. For the average household, there are definitely some appliances missing: Washing machine, dish washer, cooking range/small oven, most importantly a refrigerator!

- Tools: Router, table saw, vacuum cleaner, chainsaw, ...

*''What are your suggestions for improvement in OSE Europe?''
(tbd)

==='''WHAT''' are your skills?===

*''List all of your skills in these areas, at what level (beginner, intermediate, advanced) and where did you practice them:''
**Humor - advanced, dark and filthy
**Natural Building - earthship design basics, geodesic structures
**Woodworking - intermediate. I worked as a carpenter some time ago. And I carved a spoon once.
**Electronics - advanced. I prefer SMD over THT. I own more dev kits than jackets. My DSO has 4 channels.
**Automation - intermediate. The light in my bathroom is automatically switched with a pyroelectric sensor.
**Engineering - advanced
**CAD Design - beginner
**Energy - advanced -> power sources, renewable energy, efficiency calculations, grid layout, power consumption, rectifying techniques, power supplies, inverters, off-grid-systems
**CNC - advanced -> construction, maintenance of stepping motor and servo driven machines, retrofitting lathes and milling machines with modern hardware, LinuxCNC (formerly EMC2, the enhanced machine controller)
**Product Design - advanced <-> working at etemu.com prototyping

*''How have you already contributed to OSE, OSE Europe and Open Source Hardware?''
I include the OSHW logo in any of my open source PCB and hardware designs.
I talk about it and work actively on projects like the [[Germany/Wind_Turbine]] or [[TiVA]]

===HOW can you help?===

*''How do you want to contribute?''
Giving advice in engineering and bringing new inventions to life. Creating [[OSE_Europe/Germany|OSE Community in Germany]]

*''Are you interested in working with us for pay? If so, what services can you offer, and what is your hourly or per-project rate?''
Yes, e.g. I could provide special parts machined on a lathe.

*''Are you interested in building GVCS or other Open Source Hardware equipment in Europe? If so which ones?''
Yes. It would make sense to begin with the power sources and tools. And I would like to invent new designs rather than just copy the GVCS stuff.

*''Are you an OSE [[True Fans|True Fan]]?''
No.

*''Would you like to see yourself working with us on a full-time basis?''
Only if I would get something in exchange for my work. This could be one or more of the following
*high quality tools
*Parmiggiano Reggiano in huge amounts
*certain women
*drugs<ref>just kidding</ref>
*a digital medium format camera; Hasselblad H3D

What I won't accept:

*pets or animals in any form (except maybe if they are ''extremely'' extraordinary cute)
*Nokia smartphones
*most women
*drugs<ref>seriously</ref>
*DVDs or CDs, I got rid of any DVD drive long ago.

[[Category:Team Culturing Europe]] [[Category:Profiles Germany]]

<references />

Germany/TiVA

2012-05-13T15:30:16Z

Alex Shure: /* TiVA design outlines */

==Introduction==
Part of the modular [[Germany/Wind_Turbine|wind turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

* 16 high power RGB common anode LEDs<ref>attached to aluminium star shaped heatsinks, each with three 350 mA rgb emitters, 3 Wcontinuos, 4,6 Wpeak. best light vs current value may be at 180-260 mA, still visible from long distances. </ref>
* 6 AA NiMH cells, 2950 mAh
* 1 battery holder for 4 AA cells
* 4 MSP430 dev kits with debugging and hardware flash emulation.
* 11 NRF24L01+ 2.4 GHz 0dBm wireless transceiver modules<ref>(3V3) populated on a small SMD board, PCB antenna</ref>
* 8 LM2596 DC/DC step-down buck converter modules<ref>IN: 4-40(memo:check cap ratings!), OUT: 3,2-26, populated on a small SMD board. <200khz. iirc 70-90%, could be tuned with better coils.</ref>
* 19 IRF530 n-channel MOSFETs (no logic level types)
* various SMD resistors, also some shunt-suitable values in 1206

===Apollo-NG===
FIXME: e.g. full workflow for PCB prototyping... spray etching machine...

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

|<m>P_{wind}</m>| is the power, which is available in the wind, as kinetic energy|
|<m>\rho</m>|Density of air = about 1.2 Kg/m³ |
|<m>A_{wind}</m>|Area of turbine |
|<m>v_{wind}</m>|Wind speed in m/s |

Estimated Wind-Power conversion (mechanical):

<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>

while

<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</m>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<m>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</m>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''Wilssen''==

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring all parameters.
''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

Current sensing:
*Passive on-board shunt resistor (only for low currents) via OpAmp -> 10bit< ADC
*ACS712 integrated hall sensor with drift compensation with 1.2 mOhms(5A, 20A, 50A versions available) -> 10bit< ADC

What micro controller platform should we choose for ''Wilssen''?
*AVR: Atmel ATmega328 (AU, PU) (pico power series) (8bit)
*MSP430: Value line, e.g. MSP430G2231IPN14 (16bit)

One MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

<blockquote>
>[[Alex]]: I have 6 MSP430 in a DIP form factor in my lab and 3 spare ti MSP430 Launchpad proto boards with onboard hardware flash emulator and debugger. (...) 
>>[[Chrono]]: (...) I'd really recommend staying on avr for bigger projects since many people can do arduino now, so they
won't have to much trouble with pure avr. Another arch always reduces the amount of people who can deal with it yet :( 
>[[Alex]]: (...) I don't have the tools for AVR, except an Arduino. So no debugging, HV-programming or hardware emulation. The full dev kit for an MSP430 is dirt cheap at $4.30, including two MSP430s in DIPs, a hardware emulator, spy-by-wire, debugging etc. 
I agree with the Arudino-publicity argument, and I would always try to incorporate an Arduino, as it is the most simple and comprehensive development tool there is for beginners. However, the ti.MSP430s are relatively new. A downside is their not-so-easy dev environment. Eclipse or IAR or proprietary, free software from ti can be used. I have not yet experimented with it, but I have Arduino experience. It would be new for the both of us.
</blockquote>

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for $4.30 vs Arduino $25 or a third-party Arduino for maybe $18. This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

At a small production run of 10 TIVAs and the demand for USB ISP, Arduino vs MSP430 would equal 10*$25 = $250.00 vs 10*$4.30 = 43.00 (!)

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

[[Category: Wind energy]]

<references />

Germany/Wind Turbine

2012-05-13T15:29:44Z

Alex Shure: /* Team */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
[[File:DSC08567_edit_tiva_session.jpg|512px|thumb|right|3D modelling session for [[TiVA]] with [[Alex Shure]] and Mario.]]
If you want to participate, just get in touch at our [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – lead designer, research and development, modeling, prototyping
* Mario - 3D modelling
* Achmed - 3D modelling, simulation with OpenFOAM
* [[chrono]] (is currently not available)
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to donate any material or machine which could come in handy for us.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.
* 20120512 [[Alex Shure]] 3D modelling session with Mario, finished [[TiVA]]'s rotor base and began with the Lenz2 lift/drag hybrid wing profile.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1, i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: Wind energy]]

Germany/TiVA

2012-05-13T15:27:49Z

Alex Shure: /* TiVA design outlines */

==Introduction==
Part of the modular [[Germany/Wind_Turbine|wind turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

* 16 high power RGB common anode LEDs<ref>attached to aluminium star shaped heatsinks, each with three 350 mA rgb emitters, 3 Wcontinuos, 4,6 Wpeak. best light vs current value may be at 180-260 mA, still visible from long distances. </ref>
* 6 AA NiMH cells, 2950 mAh
* 1 battery holder for 4 AA cells
* 4 MSP430 dev kits with debugging and hardware flash emulation.
* 11 NRF24L01+ 2.4 GHz 0dBm wireless transceiver modules<ref>(3V3) populated on a small SMD board, PCB antenna</ref>
* 8 LM2596 DC/DC step-down buck converter modules<ref>IN: 4-40(memo:check cap ratings!), OUT: 3,2-26, populated on a small SMD board. <200khz. iirc 70-90%, could be tuned with better coils.</ref>
* 19 IRF530 n-channel MOSFETs (no logic level types)
* various SMD resistors, also some shunt-suitable values in 1206

===Apollo-NG===
FIXME: e.g. full workflow for PCB prototyping... spray etching machine...

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|400px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

|<m>P_{wind}</m>| is the power, which is available in the wind, as kinetic energy|
|<m>\rho</m>|Density of air = about 1.2 Kg/m³ |
|<m>A_{wind}</m>|Area of turbine |
|<m>v_{wind}</m>|Wind speed in m/s |

Estimated Wind-Power conversion (mechanical):

<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>

while

<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</m>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<m>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</m>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''Wilssen''==

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring all parameters.
''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

Current sensing:
*Passive on-board shunt resistor (only for low currents) via OpAmp -> 10bit< ADC
*ACS712 integrated hall sensor with drift compensation with 1.2 mOhms(5A, 20A, 50A versions available) -> 10bit< ADC

What micro controller platform should we choose for ''Wilssen''?
*AVR: Atmel ATmega328 (AU, PU) (pico power series) (8bit)
*MSP430: Value line, e.g. MSP430G2231IPN14 (16bit)

One MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

<blockquote>
>[[Alex]]: I have 6 MSP430 in a DIP form factor in my lab and 3 spare ti MSP430 Launchpad proto boards with onboard hardware flash emulator and debugger. (...) 
>>[[Chrono]]: (...) I'd really recommend staying on avr for bigger projects since many people can do arduino now, so they
won't have to much trouble with pure avr. Another arch always reduces the amount of people who can deal with it yet :( 
>[[Alex]]: (...) I don't have the tools for AVR, except an Arduino. So no debugging, HV-programming or hardware emulation. The full dev kit for an MSP430 is dirt cheap at $4.30, including two MSP430s in DIPs, a hardware emulator, spy-by-wire, debugging etc. 
I agree with the Arudino-publicity argument, and I would always try to incorporate an Arduino, as it is the most simple and comprehensive development tool there is for beginners. However, the ti.MSP430s are relatively new. A downside is their not-so-easy dev environment. Eclipse or IAR or proprietary, free software from ti can be used. I have not yet experimented with it, but I have Arduino experience. It would be new for the both of us.
</blockquote>

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for $4.30 vs Arduino $25 or a third-party Arduino for maybe $18. This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

At a small production run of 10 TIVAs and the demand for USB ISP, Arduino vs MSP430 would equal 10*$25 = $250.00 vs 10*$4.30 = 43.00 (!)

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

[[Category: Wind energy]]

<references />

File:20120513LXM08559 LX-M.de TiVA CAD-003.jpg

2012-05-13T15:26:33Z

Alex Shure: We encourage the use of CAE and work with 2D/3D CAD.

We encourage the use of CAE and work with 2D/3D CAD.

Germany/Wind Turbine

2012-05-13T14:27:34Z

Alex Shure: /* Team */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
[[File:DSC08567_edit_tiva_session.jpg|thumb|alt=3D modelling session for [[TiVA]] with [[Alex Shure]] and Mario.]]
If you want to participate, just get in touch at our [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – lead designer, research and development, modeling, prototyping
* Mario - 3D modelling
* Achmed - 3D modelling, simulation with OpenFOAM
* [[chrono]] (is currently not available)
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to donate any material or machine which could come in handy for us.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.
* 20120512 [[Alex Shure]] 3D modelling session with Mario, finished [[TiVA]]'s rotor base and began with the Lenz2 lift/drag hybrid wing profile.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1, i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: Wind energy]]

File:DSC08567 edit tiva session.jpg

2012-05-13T14:23:11Z

Alex Shure: 3D Modelling session for TiVA with Alex Shure and Mario.

3D Modelling session for [[TiVA]] with [[Alex Shure]] and Mario.

Germany/Wind Turbine

2012-05-13T13:47:36Z

Alex Shure: /* Open Tasks */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
If you want to participate, just get in touch at our [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – lead designer, research and development, modeling, prototyping
* Mario - 3D modelling
* Achmed - 3D modelling, simulation with OpenFOAM
* [[chrono]] (is currently not available)
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to donate any material or machine which could come in handy for us.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.
* 20120512 [[Alex Shure]] 3D modelling session with Mario, finished [[TiVA]]'s rotor base and began with the Lenz2 lift/drag hybrid wing profile.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1, i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: Wind energy]]

Germany/Wind Turbine

2012-05-13T13:45:51Z

Alex Shure: /* Team */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
If you want to participate, just get in touch at our [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – lead designer, research and development, modeling, prototyping
* Mario - 3D modelling
* Achmed - 3D modelling, simulation with OpenFOAM
* [[chrono]] (is currently not available)
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to participate.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.
* 20120512 [[Alex Shure]] 3D modelling session with Mario, finished [[TiVA]]'s rotor base and began with the Lenz2 lift/drag hybrid wing profile.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1, i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: Wind energy]]

Germany/Wind Turbine

2012-05-13T13:39:01Z

Alex Shure: /* Roadmap / Log */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
If you want to participate add your name and how you want to participate here, also please introduce yourself in the [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – research and development
* Mario - 3D modelling
* Achmed - 3D modelling
* [[chrono]] -
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to participate.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.
* 20120512 [[Alex Shure]] 3D modelling session with Mario, finished [[TiVA]]'s rotor base and began with the Lenz2 lift/drag hybrid wing profile.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1, i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: Wind energy]]

Germany/Wind Turbine

2012-05-13T13:22:56Z

Alex Shure: /* Roadmap / Log */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
If you want to participate add your name and how you want to participate here, also please introduce yourself in the [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – research and development
* Mario - 3D modelling
* Achmed - 3D modelling
* [[chrono]] -
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to participate.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.
* 20120512 [[Alex Shure]] 3D modelling session of [[TiVA]]s rotor base and the Lenz2 lift/drag hybrid wing profile.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1, i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: Wind energy]]

Germany/TiVA

2012-05-12T11:57:19Z

Alex Shure: /* Main Controller: Wilssen */

==Introduction==
Part of the modular [[Germany/Wind_Turbine|wind turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

* 16 high power RGB common anode LEDs<ref>attached to aluminium star shaped heatsinks, each with three 350 mA rgb emitters, 3 Wcontinuos, 4,6 Wpeak. best light vs current value may be at 180-260 mA, still visible from long distances. </ref>
* 6 AA NiMH cells, 2950 mAh
* 1 battery holder for 4 AA cells
* 4 MSP430 dev kits with debugging and hardware flash emulation.
* 11 NRF24L01+ 2.4 GHz 0dBm wireless transceiver modules<ref>(3V3) populated on a small SMD board, PCB antenna</ref>
* 8 LM2596 DC/DC step-down buck converter modules<ref>IN: 4-40(memo:check cap ratings!), OUT: 3,2-26, populated on a small SMD board. <200khz. iirc 70-90%, could be tuned with better coils.</ref>
* 19 IRF530 n-channel MOSFETs (no logic level types)
* various SMD resistors, also some shunt-suitable values in 1206

===Apollo-NG===
FIXME: e.g. full workflow for PCB prototyping... spray etching machine...

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==

<50cm long parts can be cut out at almost every small CNC machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

|<m>P_{wind}</m>| is the power, which is available in the wind, as kinetic energy|
|<m>\rho</m>|Density of air = about 1.2 Kg/m³ |
|<m>A_{wind}</m>|Area of turbine |
|<m>v_{wind}</m>|Wind speed in m/s |

Estimated Wind-Power conversion (mechanical):

<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>

while

<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</m>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<m>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</m>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''Wilssen''==

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring all parameters.
''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

Current sensing:
*Passive on-board shunt resistor (only for low currents) via OpAmp -> 10bit< ADC
*ACS712 integrated hall sensor with drift compensation with 1.2 mOhms(5A, 20A, 50A versions available) -> 10bit< ADC

What micro controller platform should we choose for ''Wilssen''?
*AVR: Atmel ATmega328 (AU, PU) (pico power series) (8bit)
*MSP430: Value line, e.g. MSP430G2231IPN14 (16bit)

One MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

<blockquote>
>[[Alex]]: I have 6 MSP430 in a DIP form factor in my lab and 3 spare ti MSP430 Launchpad proto boards with onboard hardware flash emulator and debugger. (...) 
>>[[Chrono]]: (...) I'd really recommend staying on avr for bigger projects since many people can do arduino now, so they
won't have to much trouble with pure avr. Another arch always reduces the amount of people who can deal with it yet :( 
>[[Alex]]: (...) I don't have the tools for AVR, except an Arduino. So no debugging, HV-programming or hardware emulation. The full dev kit for an MSP430 is dirt cheap at $4.30, including two MSP430s in DIPs, a hardware emulator, spy-by-wire, debugging etc. 
I agree with the Arudino-publicity argument, and I would always try to incorporate an Arduino, as it is the most simple and comprehensive development tool there is for beginners. However, the ti.MSP430s are relatively new. A downside is their not-so-easy dev environment. Eclipse or IAR or proprietary, free software from ti can be used. I have not yet experimented with it, but I have Arduino experience. It would be new for the both of us.
</blockquote>

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for $4.30 vs Arduino $25 or a third-party Arduino for maybe $18. This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

At a small production run of 10 TIVAs and the demand for USB ISP, Arduino vs MSP430 would equal 10*$25 = $250.00 vs 10*$4.30 = 43.00 (!)

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

[[Category: Wind energy]]

<references />

Germany/TiVA

2012-05-11T13:19:51Z

Alex Shure: added conclusions from NACA0018 testing, corrected spelling mistakes

==Introduction==
Part of the modular [[Germany/Wind_Turbine|wind turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

* 16 high power RGB common anode LEDs<ref>attached to aluminium star shaped heatsinks, each with three 350 mA rgb emitters, 3 Wcontinuos, 4,6 Wpeak. best light vs current value may be at 180-260 mA, still visible from long distances. </ref>
* 6 AA NiMH cells, 2950 mAh
* 1 battery holder for 4 AA cells
* 4 MSP430 dev kits with debugging and hardware flash emulation.
* 11 NRF24L01+ 2.4 GHz 0dBm wireless transceiver modules<ref>(3V3) populated on a small SMD board, PCB antenna</ref>
* 8 LM2596 DC/DC step-down buck converter modules<ref>IN: 4-40(memo:check cap ratings!), OUT: 3,2-26, populated on a small SMD board. <200khz. iirc 70-90%, could be tuned with better coils.</ref>
* 19 IRF530 n-channel MOSFETs (no logic level types)
* various SMD resistors, also some shunt-suitable values in 1206

===Apollo-NG===
FIXME: e.g. full workflow for PCB prototyping... spray etching machine...

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==

<50cm long parts can be cut out at almost every small CNC machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

|<m>P_{wind}</m>| is the power, which is available in the wind, as kinetic energy|
|<m>\rho</m>|Density of air = about 1.2 Kg/m³ |
|<m>A_{wind}</m>|Area of turbine |
|<m>v_{wind}</m>|Wind speed in m/s |

Estimated Wind-Power conversion (mechanical):

<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>

while

<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</m>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<m>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</m>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''Wilssen''==

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring all parameters.
''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

What micro controller platform should we choose for ''Wilssen''?

* one MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

<blockquote>
>[[Alex]]: I have 6 MSP430 in a DIP form factor in my lab and 3 spare ti MSP430 Launchpad proto boards with onboard hardware flash emulator and debugger. (...) 
>>[[Chrono]]: (...) I'd really recommend staying on avr for bigger projects since many people can do arduino now, so they
won't have to much trouble with pure avr. Another arch always reduces the amount of people who can deal with it yet :( 
>[[Alex]]: (...) I don't have the tools for AVR, except an Arduino. So no debugging, HV-programming or hardware emulation. The full dev kit for an MSP430 is dirt cheap at $4.30, including two MSP430s in DIPs, a hardware emulator, spy-by-wire, debugging etc. 
I agree with the Arudino-publicity argument, and I would always try to incorporate an Arduino, as it is the most simple and comprehensive development tool there is for beginners. However, the ti.MSP430s are relatively new. A downside is their not-so-easy dev environment. Eclipse or IAR or proprietary, free software from ti can be used. I have not yet experimented with it, but I have Arduino experience. It would be new for the both of us.
</blockquote>

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for $4.30 vs Arduino $25 or a third-party Arduino for maybe $18. This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

At a small production run of 10 TIVAs and the demand for USB ISP, Arduino vs MSP430 would equal 10*$25 = $250.00 vs 10*$4.30 = 43.00 (!)

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#watchdog V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

<references />

Germany/Wind Turbine

2012-05-11T11:51:45Z

Alex Shure: /* Roadmap / Log */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
If you want to participate add your name and how you want to participate here, also please introduce yourself in the [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – research and development
* Mario - 3D modelling
* Achmed - 3D modelling
* [[chrono]] -
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to participate.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D-modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1, i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

Germany/Events

2012-05-07T17:10:34Z

Alex Shure: /* May */

{{Germany}}

Events for OSE Germany:
==May==
* 04.-06.05 - OSE Präsentation auf [http://osede.org/up/events/NANK-eV_T-NANK-Programm-04-05-2012_27-04-2012.pdf NANK Netzwerktreffen in Wuppertal].
* 25.-26.05 - Erstes Teamtreffen in Berlin. Mehr Infos bald.
* 30.05. - Solar World in Bochum
* 31.05 - OSE Präsentation auf der [http://www.karmakonsum.de/konferenz/ KarmaKonsum 2012] in Frankfurt.

==June==
* 01.06 - OSE Workshop auf der [http://www.karmakonsum.de/konferenz/ KarmaKonsum 2012] in Frankfurt.

[[Category: OSE Germany]]

Germany/Wind Turbine

2012-05-07T12:51:04Z

Alex Shure: /* How does the wind turbine generate energy? */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
If you want to participate add your name and how you want to participate here, also please introduce yourself in the [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – research and development
* [[chrono]] -
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to participate.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D-modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1, i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

Germany/Wind Turbine

2012-05-07T12:36:32Z

Alex Shure: /* How does the wind turbine generate energy? */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
If you want to participate add your name and how you want to participate here, also please introduce yourself in the [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – research and development
* [[chrono]] -
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to participate.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D-modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1, i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 16 degrees. However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

Germany/Wind Turbine

2012-05-07T12:25:13Z

Alex Shure: /* How does the wind turbine generate energy? */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
If you want to participate add your name and how you want to participate here, also please introduce yourself in the [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – research and development
* [[chrono]] -
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to participate.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D-modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> >> 1. It generates more lift for the 180 degrees the blade is coming into the wind, and less lift when the blade is moving the same direction as the wind - but it still produces lift for almost the entire revolution, because the blades are moving faster than the wind is moving. This is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 16 degrees. However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

Germany/Wind Turbine

2012-05-07T12:14:41Z

Alex Shure: /* How does the wind turbine generate energy? */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
If you want to participate add your name and how you want to participate here, also please introduce yourself in the [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – research and development
* [[chrono]] -
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to participate.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D-modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift the full 360 degree rotation, as long as you have a TSR<ref>Tip Speed Ratio</ref> 1<<. It generates more lift for the 180 degrees the blade is coming into the wind, and less lift when the blade is moving the same direction as the wind - but it still produces lift the entire 360 degrees, because the blades are moving faster than the wind is moving. This is why airplanes fly.

A drag type VAWT has always a TSR <1, and the blades capture energy for 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

Germany/Wind Turbine

2012-05-04T19:32:40Z

Alex Shure: /* Roadmap / Log */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
If you want to participate add your name and how you want to participate here, also please introduce yourself in the [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – research and development
* [[chrono]] -
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to participate.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D-modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

Germany/Wind Turbine

2012-05-04T19:27:25Z

Alex Shure: /* Open Tasks */

{{Germany}}
==Status==

The '''wind turbine''' is in the research phase of product development, we are focusing on the '''[[TiVA]]'''-System right now.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and [[Germany/Wind_Turbine|wind turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
If you want to participate add your name and how you want to participate here, also please introduce yourself in the [[Germany/Communication#Google_Group|Google Group]].

* [[Alex Shure]] – research and development
* [[chrono]] -
* [[Nikolay Georgiev]] - communication and organization

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
* Development of ''Wilssen'':
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters.
''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.
* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to participate.

==Roadmap / Log==

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D-modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter.<ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>C_d</m> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> = Area of turbine = max 4 m² 
<m>v_{wind}</m> = Wind speed in m/s

:<m>F ({50\frac{m}{s}) = \frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</m>
:<m>F ({30\frac{m}{s}) = 2160 N</m>
:<m>F ({20\frac{m}{s}) = 960 N</m>
:<m>F ({10\frac{m}{s}) = 240 N</m>
:<m>F ({5\frac{m}{s}) = 60 N</m>

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <m>F ({30\frac{m}{s}) = 2160 N</m>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<m>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</m>

<m>P_{wind}</m> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<m>\rho</m> = Density of air = about 1.2 Kg/m³ 
<m>A_{wind}</m> = Area of turbine = max 4 m² at a small scale turbine 
<m>v_{wind}</m> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<m>P_{mech}=P_{wind} \times \rho_{turbine} </m>
while 
<m>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 35% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50% \\
\rho_{limit} = 59% \\
</m> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

Germany/People

2012-05-04T18:59:44Z

Alex Shure:

{{Germany}}

We are developing OSE Germany:

* [[Alex Shure]] (Berlin) – Technical advice, prototyping, proofreading, [[Germany/Wind_Turbine|Wind Turbine]], [[TiVA]], [[Germany/OSE_Community|OSE Community]]
* [[Andre Jonas]] (Kiel) – Translation and proofreading
* [[Andreas Gmeiner]] (Regensburg) – [[Germany/OSE_Community|OSE Community]], Ecology, Permaculture, 3D Printing
* Mabe, Mister Scr3wdriv3r (Freiburg) - [[CNC Circuit Mill]]
* [[Nikolay Georgiev]] (Darmstadt) – Communication and Organization, [[Germany/OSE_Community|OSE Community]], [[Germany/Wind_Turbine|Wind Turbine]], [[Germany/Distributive_Enterprise|Distributive Enterprise]]
* [[Paul Leidorf]] (Hamburg) - CAD, translation
* [[Tim-Rasmus_Kiehl|Rasmus Kiehl]] (Toronto, Canada) - [[biochar]], [[Medical_Swadeshi|medical swadeshi]], [[microfluidics|low-cost diagnostics]], [[Integrated_Food_and_Waste_Management_System|integrated farming]]

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<iframe width="600" height="540" frameborder="0" scrolling="no" marginheight="0" marginwidth="0" src="http://maps.google.de/maps/ms?msa=0&msid=209565165832430470075.0004adf47cafeceb806f8&hl=en&ie=UTF8&t=h&ll=51.165567,10.063477&spn=7.443174,13.183594&z=6&output=embed"></iframe> View <a href="http://maps.google.de/maps/ms?msa=0&msid=209565165832430470075.0004adf47cafeceb806f8&hl=en&ie=UTF8&t=h&ll=51.165567,10.063477&spn=7.443174,13.183594&z=6&source=embed" style="color:#0000FF;text-align:left">OSE - Europe (official)</a> in a larger map
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People who have helped us and are currently inactive:
* [[Jalil Wahdatehagh]] (Munich) – Media Design and Production

Note: we add people to the list only if they are: 1) already in contact with some people from the list and 2) contributing to the OSE development in Germany.

[[Category: OSE Germany]]