http://web.mit.edu/newsoffice/2011/thermo-photovoltaics-1202.htmlA novel way to concentrate sun’s heat
MIT researchers find a way to generate power without the usual mirror arrays.
David L. Chandler, MIT News Office
December 2, 2011
Most technologies for harnessing the sun’s energy capture the light itself, which is turned into electricity using photovoltaic materials. Others use the sun’s thermal energy, usually concentrating the sunlight with mirrors to generate enough heat to boil water and turn a generating turbine. A third, less common approach is to use the sun’s heat — also concentrated by mirrors — to generate electricity directly, using solid-state devices called thermophotovoltaics, which have their roots at MIT dating back to the 1950s.
Now, researchers at MIT have found a way to use thermophotovoltaic devices without mirrors to concentrate the sunlight, potentially making the system much simpler and less expensive. The key is to prevent the heat from escaping the thermoelectric material, something the MIT team achieved by using a photonic crystal: essentially, an array of precisely spaced microscopic holes in a top layer of the material.
The approach mimics Earth’s greenhouse effect: Infrared radiation from the sun can enter the chip through the holes on the surface, but the reflected rays are blocked when they try to escape. This blockage is achieved by a precisely designed geometry that only allows rays that fall within a very tiny range of angles to escape, while the rest stay in the material and heat it up.
The new device was
http://www.nanoscalereslett.com/content/6/1/549">described in a paper by Research Laboratory of Electronics research scientist Peter Bermel and other MIT researchers, published in October in the journal
Nanoscale Research Letters.
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