500 times seems too high. I gather the parabolic troughs used at SEGS
in California only concentrate sunlight by a factor of 80 and yet
they heat the devices up to 400 deg C.
How do you concentrate sunlight 500 times? With a Fresnel lens?
Parabolic trough? It seems to me if you are going to the trouble to
do that, the thing will be pretty hot and you might as well go with
large scale solar thermal steam generator or Stirling engine. I
expect they are also ~30% efficient but lot simpler and cheaper.
- Jed
