Wind Turbine

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Open Source Ecology is involved in researching, developing and building open-source technologies for clean, local electricity-generation. As well as solar power, we like wind power. Wind power or solar or both may be appropriate, depending on local materials and local weather conditions.

Specifically, we are interested in open-source designs for a wind turbine that can provide electricity for a small community. Small wind turbines like this are usually 7 feet (2m) to 25 feet (7.6m) in diameter.

Design specifications

Wanted: We need to define exactly what we need from our wind turbine. Edit this list.

• Scalability - scalable from ??? to ???
• Low-cost - must cost less than $1 per installed watt and $0.05/kWh produced on a medium speed site (6m/s average speed [13.4mph, 21.6km/h])
• CAD files to allow parts to be digitally fabricated. We could just take an existing open-source design, and get one of our draftsmen to make the CAD file. Good CAD files could allow for scalable digital fabrication: the blades could be printed in a range of sizes, depending on what you need

Existing open-source wind turbines

Several wind turbines have already been open-sourced and it should be possible to use them for the Global Village Construction Set:

• Zoetrope is a vertical-axis wind turbine made from common materials such as stove pipe, metal brackets, plastic sheet and a trailer hub. Generates about 150-200W in winds of 20mph (32km/h). Construction Guide. The major parts are: parts kit for $159 (unless you could order one from a Fab Lab/ a hackerspace with a water-jet cutter), 24 neodymium magnets for $140, trailer hub for $26. There are also a bunch of pieces like nuts and bolts, but those are the main one, and come to $425 excluding shipping.
• OtherPower.com have several complete plans for wind turbines that can be built at home. Their site has -
  • Complete plans for a 10 foot (3m) turbine that puts out 100W in 10mph (16km/h) winds and 700W in 25mph (40km/h) winds.
  • Design of a 14 foot (4.25m) turbine that does 200W in 10mph (16km/h) winds and 1500W in 25mph (40km/h) winds. This is the record of a project rather than a replicable open-source design.
• Chispito Wind Generator. Chispito is made from recycled/salvaged materials, completely open-source with clear instructions and designed for simplicity. Open-source instructions for building both the turbine and the tower are available. Each turbine generates about 100W; most people seem to use a bunch of them. This is probably smaller that what we are looking for.
• http://www.scoraigwind.com/ has a lot of information on wind turbines, but no fully open-source plan
• Open source alternator for wind turbines
• Onawi is a not-for-profit organization dedicated to developing open-source wind turbines. No signs of progress yet, but watch this space.

What kind of turbine?

The first design decision we have to make is which kind of wind generator best suits our needs

Vertical Axis Wind Turbine|Vertical-axis wind turbines

Pacwind VAWT Vertical Axis Wind Turbine Seahawk

Verical Axis Wind Turbines or VAWTs offer a number of advantages over traditional horizontal-axis wind turbines (HAWTs). They can be packed closer together in wind farms, allowing more in a given space. This is not because they are smaller, but rather due to the slowing effect on the air that HAWTs have, forcing designers to separate them by ten times their width. VAWTs are rugged, quiet, omni-directional, and they do not create as much stress on the support structure. They do not require as much wind to generate power, thus allowing them to be closer to the ground. By being closer to the ground they are easily maintained and can be installed on chimneys and similar tall structures.

In addition, by being closer to the ground, VAWTs have the ability to take advantage of the tunnelling effects of small buildings and structures (provided the structures are build close enough) small VAWTs are also used in corners of buildings (usually the corner of a balcony).

Although VAWTs are not as efficient as HAWTs they are considered more reliable and much easier to maintain. One disadvantage of the VAWT is that the blade that moves into the wind also moves against the wind, slowing down the turbine. This could be addressed by a shield that adjusts to the direction of the wind and covers the blade that moves into the wind. This could be done with some kind of vane. However, this would complicate the design significantly, incl. bearings for the shield. So this may not be worth it ... probably easier to just build more VAWTs or build them bigger. But who knows ? Come up with a good sail/shield design and this might be just the breakthrough that VAWTs have been waiting for.

A good step by step guide can be found on this link: a small Savonius wind turbine that takes advantage of the Venturi effect.

There is a small scale printable VAWT on thingiverse http://www.thingiverse.com/thing:6899

Airborne wind turbines

A turbine attached to a lighter-than-air ballooon, such as being developed by Magenn. I think we can reject this as too complex and too experimental for our purposes.

1. Wind driven apparatus for power generation - expired patent for a tethered airborne turbine. This design generates power at the turbine and transmits it to the ground.
2. High Altitude Wind Power at PESwiki

Kite generators

A high-flying power kite tethered to a generator on the ground. The kite tugs on the tether, which spins a turbine and generates electricity. All the machinery can be kept at ground level; only the sail is airborne. This allows for easy maintenance.

The two main advantages of this design are that reaches the more powerful winds higher up, and it may come in cheaper than a turbine. This report from the WPI Kite Power Team says there is an "anticipated 50% cost savings over wind turbines".

We can probably buy an off-the-shelf power kite. Here is a 5m² one for $166. Here is a 2.7m² one for $14. This seems to be a top-of-the-range one - it's $600 for 6.5m². Alternatively, we could try to build our own kite.

This would need to be attached to the open-source electric motor we're designing, and a microcontroller. All the hardware is on the ground, which makes maintenance and set-up easier. The control will be the main design challenge.

1. Ecoble article: Wind Power Generated From Kites
2. at Delft University of Technology:Kite Power Could Generate Energy for 100,000 Homes
3. Autopilot Arduino board for drones
4. Saul Griffith on kites as the future of renewable energy
5. Academic project assessing feasibility of kite power (link is to a 109 page pdf file). Gives technical details of the mechanism. Estimates 500W from a 2m² kite if the average wind speed in 8m/s
6. http://climatelab.org/Airborne_Wind_Energy_Systems
7. WPI Kite Power Wiki - "dedicated to developing a new renewable energy technology - Wind Power from Kites. In this concept, large kites tethered to the ground are used to extract power from the wind. Kites can extract power more economically than wind turbines because they fly at higher heights than turbines can operate."
8. http://www.kitegen.com/en/?page_id=7

References

• Homebrew Wind Power, Dan Bartmann and Dan Fink, Buckville Publications LLC., released: January 1, 2009, 320 pages,

ISBN: 978-0981920108.

See also

• Wind turbine
• Wind turbine design
• Small wind turbine