On Thu, 22 Sep 2005, James Newtons Massmind wrote:

> Here is another idea: Put the mirrors on the ground. You can prop them up
> with rocks if you want. Align them at night with a laser pointer and a
> target in the center. Hang the pointer on a string from a tripod which is
> placed over each mirror like a plumb bob then move the mirror until the beam
> hits the target. Next day, you have a small copy of the sun tracking through
> the air over the mirror field.
>
> Then, put the engine and generator in the air on a post and move them to
> match the focal point of the mirrors. Since there is no high pressure feed
> to run to the motor and no hot exhaust to run out, the only thing that needs
> to follow them is a water hose going in, and an electrical cable going out.
> I would probably use two arms and a pole between them with the motor /
> generator mounted in the middle.

http://www.answers.com/topic/heliostat

I don't know where Barstow is, but it says it's in California. Here are 
two pdf documents that show what has been realised:

http://www.iaec.gov.il/docs/IAEC11.pdf

This has an optical scheme that may be scaled for smaller installations. 
The focal point is on the ground.

http://www.docrenewableenergy.info/en_path-en%5Crenewable+energy%2Fthermal+solar~id-10337~action-download~url-http:%2F%2F66.102.9.99%2Furl%3Fsa%3DU&start%3D138&q%3Dhttp:%2F%2Fwww.solarpaces.org%2FEUREC-Position_Paper_STPP.pdf&e%3D747~title-Solar+Thermal+Power+Plants

The Almeria plant also has Stirling motors mounted directly at the focal 
point of parabolic mirrors (big ones).

Peter
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