NEW SOLAR USES HEAT + LIGHT

New Solar Energy Conversion Process Could Double Solar Efficiency of Solar Cells
August 2, 2010 (Science Daily)

"Stanford engineers have figured out how to simultaneously use the light and heat of the sun to generate electricity in a way that could make solar power production more than twice as efficient as existing methods and potentially cheap enough to compete with oil.

"Unlike photovoltaic technology currently used in solar panels -- which becomes less efficient as the temperature rises -- the new process excels at higher temperatures…Called "photon enhanced thermionic emission," or PETE, the process promises to surpass the efficiency of existing photovoltaic and thermal conversion technologies…And the materials needed to build a device to make the process work are cheap and easily available, meaning the power that comes from it will be affordable…"

The cesium and gallium nitride PETE that proved the concept. (click to enlarge)

"Until now, no one had come up with a way to wed thermal and solar cell conversion technologies…[C]oating a piece of [gallium nitride] semiconducting material with a thin layer of the metal cesium, it made the material able to use both light and heat to generate electricity…[A semiconductor such as gallium arsenide, used in household electronics, could increase the efficiency]…

"While most silicon solar cells have been rendered inert by the time the temperature reaches 100 degrees Celsius, the PETE device doesn't hit peak efficiency until it is well over 200 degrees C…[It] performs best at temperatures well in excess of what a rooftop solar panel would reach…[so] will work best in solar concentrators…which can get as hot as 800 degrees C…and usually include a thermal conversion mechanism as part of their design, which offers another opportunity for PETE to help generate electricity, as well as minimizing costs by meshing with existing technology…"