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Lens arrays show potential for Solar Concentrators

Photonics Spectra
Mar 2015
STATE COLLEGE, Pa. — ‘The simplicity of this solution is really what gives it practical value.’ - Penn State professor Dr. Noel C. Giebink

Tiny solar cells sandwiched between lens arrays could shrink concen- trator photovoltaics (CPVs) down to a consumer scale.

Solar Panels
Smaller concentrator photovoltaics (CPVs) could improve solar cell efficiency at the consumer level.


“Current CPV systems are the size of billboards and have to be pointed very accurately to track the sun throughout the day,” said Pennsylvania State University professor Dr. Noel C. Giebink. “But you can’t put a system like this on your roof, which is where the majority of solar panels throughout the world are installed.”

Giebink led an international team that developed a prototype rooftop CPV incorporating high-efficiency GaAs cells less than a millimeter in size that need to move no more than a centimeter to keep up with the sun. Funded by the U.S. Department of Energy, the research was published in Nature Communications (doi: 10.1038/ncomms7223).

The cells were embedded between a pair of 3-D-printed plastic lens arrays less than a centimeter thick. Each lens in the top array acts as a small magnifying glass and is matched to a lens in the bottom array that functions as a concave mirror.

With each tiny solar cell located at the focal point of the two optics, sunlight is intensified more than 200 times. An optical oil lubricates the sliding cell array and also improves light transmission.

“The vision is that such a microtracking CPV panel could be placed on a roof in the same space as a traditional solar panel and generate a lot more power,” Giebink said. “The simplicity of this solution is really what gives it practical value.”

Giebink said that improving consumer solar cell efficiency from the current 20 percent for silicon toward 40 percent or better with multijunction CPVs is important because increasing the power generated by a given system reduces the overall cost of the electricity it generates.

He cautioned, however, that CPV systems are not suitable for all locations.

“CPV only makes sense in areas with lots of direct sunlight, like the American Southwest,” he said. “In cloudy regions like the Pacific Northwest, CPV systems can’t concentrate the diffuse light, and they lose their efficiency advantage.”


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