Ultra-Efficient Solar Cells Can Be Adapted for Rooftops, Researchers Say

Extremely efficient solar cells similar to those used in space may soon be ready for installation on residential rooftops, according to a report in Nature Communications.  Concentrated photovoltaic (CPV) systems, which use lenses and curved mirrors to focus sunlight onto small solar cells, produce energy much more efficiently than conventional solar panels — 40-percent efficiency compared to less than 20 percent for standard silicon systems.  But they are typically the size of billboards and have to be positioned very accurately to track the sun throughout the day.  Now researchers have overcome these obstacles by developing a CPV system that uses miniaturized gallium-arsenide photovoltaic cells, 3D-printed plastic lens arrays, and a moveable focusing mechanism.  The new system is small and light enough to fit on a residential rooftop and should be inexpensive to produce, researchers say.  A prototype in Pennsylvania was able to concentrate ambient solar energy 100 times over, although CPV systems are best suited for areas with plenty of direct sunlight, such as the U.S. Southwest, the researchers note.

"CPV only makes sense in areas with lots of direct sunlight, like the American Southwest," said Noel C. Giebink, assistant professor of electrical engineering, Penn State.  "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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