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Sustainable Energy

All-Day Solar Cells

New photovoltaics get better performance throughout the day.

Solar cells crank out the most power at noon, when the sun is at its highest point. But researchers at the Georgia Tech Research Institute have come up with a proto­type that works best in the morning and afternoon. Their solar cell, whose surface consists of hundreds of thousands of 100-­micrometer-high block-like towers (left), operates at high efficiencies through much of the day by catching light at many angles, with peak performance when the sun is at a 45° ­angle. “At an ­angle, the light has an opportunity to reflect off the sides of the towers,” says Jud Ready, senior research engineer at the institute’s Electro-­Optical Systems Laboratory.

The solar cells are still not efficient enough for commercialization, but Ready is working on optimizing the size, spacing, and chemical composition of his towers. He sees the cells finding their first applications in spacecraft and satellites; cells that don’t require mechanical means to stay sun-facing would be especially useful in space.

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