Benjamin

On Sun, Jun 15, 2008 at 10:46 PM, <ben@windwavesandsun.com> wrote:

   Dear Marcin,

   I drew up a 3D sketch of your proposal: (attached) The 3D draft can be used to render working drawings.

Excellent. Thanks. See:

http://openfarmtech.org/index.php?title=Solar_Concentrator_Technical_Drawings#Concept

You may be interested in joining the Google group Solar Turbine -

http://groups.google.com/group/solar-turbine

   Notes on Design:
   I Recommend putting the sets screws on top of the frame where they can be reached:
   This would mean increasing the size of the frame a few inches and the length of the 2"cube.
   I also note there is no wiggle room on the inside of the frame. The Tiles will be very accurately 48 inches, which is exactly the inside dimensions of the frame.

   I am quite concerned that the orientation, and non-moving nature of the design will be disappointing as the target will be fully lit for only a few hours every day.

You must consider that Length>>Height in our system - 40x10 foot array indicates that from 9 AM to 3 PM - losses due to fixed E-W position are 5/40 = 12% - or negligible for present purposes. 10' is the height of the collector. This means that a 45 degree solar angle would make you lose 5 feet of receiver space - and 5 out of 40 is acceptable for the gross simplicity of the design.

You have to recall that this system is slated to be cost effective because of the total of such simplifications. We are concerned about cost as the bottom line for feasibility.

   In particular, I note that your design appears to place the linear collectors on the east-west axis in the hopes of reducing daily tracking issues into weekly tracking adjustments. I would predict that this decision will result in a considerable amount of misdirected sunlight at both ends of the device, and that given the scale here; this will have a significant effect on the energy potential. Most linear systems track the sun throughout the day, and are aligned in the north-south direction in order to minimize the overshoot-losses.

40 foot length at 12% loss is acceptable. Longer arrays (or arrays with lower height by making the slats more narrow) make this loss negligible - as in linear trough systems - which track only the seasonal change.

   - First - I am interested in providing an electronic tracking system (based on the Open Source Hardware/Software Arduino platform) and since I have already built and tested such a device, it should be a reasonable goal.)

With the above said, we DO desire automated tracking (turning of the 16 slats to follow seasonal changes, which we will at first do on a weekly basis by hand) for seasonal change. Can you help us in the open source?

Hey, here's the bottom line. We can all work together in the open source. The way to make money and give design away for free

(see report that includes our work - www.newmediaexplorer.org/steve_bosserman/2008/02/09/giving_it_away_making_money.htm)

is to become a producer of that which you develop. You then have competitive advantage and primacy in your local bioregion. There is no substitute for good old productive work - otherwise we end up with monopolies and the system exactly as it is today - where we can't even do effective solar electric yet. Our business model is to give design away - and make money by honest labor - such as the effective production of CEB machines or solar turbines, at $50-100 per hour in labor to us. That's the core. Around this - one gets a good reputation - and consulting, speaking, workshop, teaching, and other earning opportunities arise - according to peer economy principles. Another key is to diversify - we want to produce an entire sustainable living package up to Fab Labs, cars, and electronics.

   - As for the directed question of known best practices for deriving electricity from heat - The best source I have is a geothermal contact/conversation I had at an NREL conference. He had purchased some large "compressors", I believe of the air-conditioning type - and was able to generate energy even at quite low temperatures (but I think with a propane or similar fluid). 

Yes. I've heard of this concept - sounds like organic Rankine cycle. The MIT Solar Turbine is using this, and Ausra appears to be using it. We will evaluate if water (simplest) has sufficient performance. If it doesn't we'll proceed with other fluids. If you are in contact with this guy, can you find out his practical critique of water vs. other refrigerant fluids? I understand that water: advantage: works well, easy to work with - disadvantage - corrodes metal, requires higher temperatures than other refrigerants. For other refrigerants - advantage: lower working temperature; disadvantage - harder to work with, lower efficiency per volume flow rate? Is that correct?

From what you know, is it fair to say that water works as well? We know they use steam turbines for the majority of modern electrical generation.

   - I would be happy to initiate a project - again, based on Arduino - to provide electronic control of the turbine system - using temperature sensors, pressure sensors, and tachometers for example to adjust control values - if that is necessary.

Right on. That would be desirable.

Please start with http://openfarmtech.org/index.php?title=Valve_delivery_system as the immediate need for water delivery to the turbine - via valving instead of energy-intensive pumps that work against a 100 PSI+ pressure gradient. Let me know what you think.

   - If I can arrange to make the journey, I would like to help out in August - more importantly, I think the first construction will identify potential control-related opportunities:

Abslutely. Keep Aug. 15 in mind. That's when the world's first open source solar turbine pow-wow is happening.

   I have sourced an actuator from china which costs $7 in bulk. 

I would like to really encourage you to start the open source development of said actuator. There is a large electronics open source community. OpenCores is one of the venues. We should be aiming to eliminate Chinese junk as soon as possible. The open source fab lab is a means to do so. See our work: http://openfarmtech.org/index.php?title=Open_Source_Fab_Lab