SHPEGS — DIY Solar/Geothermal Electricity

rohar writes "SHPEGS is an open design not-for-profit project to design and prototype a base-load renewable electrical generation system suitable for moderate climates and built from common materials. The design centers around creating a local geothermal source with an efficient solar thermal water heater system and can be scaled from single residence to mega-scale. The heliostat system used in Europe's first solar thermal plant could be used in a scaled-down SHPEGS system with Practical Solar's small scale heliostats."

Comments

Let's see a prototype

[Animats]

That thing has an incredibly complex cycle, with losses all along the chain. There's ammonia, water, steam, air, and hot oil involved, with heat exchangers all over the place. The paper attached to it doesn't describe the basic thermodynamics in any real detail. It's sort of like a solar-powered Rankin cycle system. But much more complex, and without solid justification for the extra complexity.

This might be credible if they had a working prototype, even a little one. A prototype in the 1 KW range would be about right. That's a backyard project. A 1KW plant would need about 10 square meters of collector mirror, which isn't too hard. Then they'd have something. All they have now is hype.

Re:Developing World Application

[rohar]

This is a very interesting project by a group of MIT grads that implemented a very cheap solar thermal system out of salvage automotive components (power steering pump, alternator, etc) for low cost deployment in developing countries.

The SHPEGS additions to this type of system (thermal storage, convection tower) could also be implemented cheaply from common materials and salvage parts.

Can anyone help with the math?

[Bodhammer]

I recently read an article about solar power in Wired magazine: http://www.wired.com/wired/archive/13.07/solar.htm l

The article mentions a new design for a concentrator that only uses two motors. To quote the article -

"Then, in a weekend flash of inspiration, a young Caltech physics grad named Kevin Hickerson figured out how to reduce the number of motors needed to move 25 mirrors independently, a major cost factor. Instead of two motors for each mirror - the traditional approach - Hickerson's solution requires only two motors for any number of mirrors. The key is a mathematical curve known as the conchoid of Nicomedes (named for the ancient Greek mathematician, who discovered it). A grid of ball bearings arrayed to match the conchoid is attached to a frame inside the Sunflower. As the motors move the frame, the bearings control each mirror's position individually."

I have found this but it is not helping me much:

http://nvizx.typepad.com/nvizx_weblog/2005/08/conc hoid_of_nic.html

I have been unable to locate a more detailed explanation of the system and I'm not sure if this basic math is patentable. My advanced math skills are very rusty and I'm not quite sure where to start to understand this. I have an idea that this technique might be useful and I want to understand how to design such a frame. I did look at the concentrator page here: http://www.sandia.gov/pv/docs/PVFarraysConcentrato r_Collectors.htm but it was not much help.

These articles as well also have some implications for the benefits of a simple energy source:

http://science.slashdot.org/article.pl?sid=05/09/1 2/1621204&tid=126&tid=14

http://www.time.com/time/magazine/printout/0,8816, 1101299,00.html

Also, this today triggered my interest again:

http://www.renewableenergyaccess.com/rea/news/stor y?id=46765

I want to understand how to make a spreadsheet or something that would allow me to input number mirrors, focal length, size and it tell me shape, size a location of pivots. Can you explain it to someone who hasn't touched calculus in 18 years? I want to build a cheap one on my roof!