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Concentrated Solar Shines Bright May 7, 2010

Posted by OldGuy in solar.
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Concentrating the sun’s rays on a smaller spot is a great approach to boosting efficiency of solar power.  It’s a half-step toward making solar economically viable.

Traditional solar thermal systems use highly concentrated sunlight to create steam that drives electric turbines.  Trouble is, that way takes massive amounts of water to create steam, but abundant clean water is coming to be one of the scarcest commodities in the world.  And taking water from fish and wildlife habitats puts you sideways from environmental regulators.

What Amonix (a California-based startup) has done is to combine Fresnel lenses, a tracking system, and solar cells for large, highly efficient solar-power installations.

Step one is the lens. I know about Fresnel lenses from theater. It takes a small light source (a bulb) and spreads it out to provide wide coverage of an area on stage. Amonix turned it around, to take a wide coverage of sunlight and concentrate it on a small solar collector. These thin, plastic Fresnel lenses, measuring about 350 square centimeters, focus sunlight down to a 0.7 square centimeters spot. That concentrates the sunlight to 500 times its normal intensity.

That concentrated sunlight hits an ultra-efficient multi-junction solar cell made by Spectrolab, the most efficient in the world. They’ve shown 41% efficiency in the lab, and Amonix is able to get 39% in field tests.

These cells are set in an array that’s 23.5 meters by 15 meters, 165 co-joined panels worth. Then Amonix uses a tracking system that keeps the lenses pointed to within .8 degrees of the angle of the sun all day long.

That’s a lot of miracles happening all at once. And we’re worried about the long-term viability of plastic lenses exposed to that much UV radiation. But at least it holds promise for the future.

source: http://www.technologyreview.com/business/25209/?a=f

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