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3-D Solar

A new dimension in photovoltaics

Most solar panels are installed horizontally across rooftops or other surfaces. Some are attached to motorized structures that keep the cells pointed toward the sun as it crosses the sky. But now MIT researchers have found that going vertical—installing solar cells on three-dimensional cubes or towers—could vastly improve the output from a solar array.

Ray catcher: One of several three-dimensional solar structures tested on an MIT rooftop.

The structures they’ve tested show power output ranging from double to more than 20 times that of fixed flat panels with the same base area. Better yet, the biggest boosts in power were seen in situations where improvements are most needed: in locations far from the equator, in winter months, and on cloudier days. The new findings, based on both computer modeling and outdoor testing of real modules, were published in Energy and Environmental Science.

“I think this concept could become an important part of the future of photovoltaics,” says the paper’s senior author, Jeffrey Grossman, an associate professor of materials science and engineering.

The MIT team initially used a computer algorithm to explore possible configurations. Then, to confirm their model’s predictions, they built three arrangements of solar cells—a simple cube, a double cube, and a complex accordionlike shape that could be shipped flat and unfolded for installation—and tested them on the roof of MIT’s Building 13 for several weeks.

When they began testing, the researchers were distressed when almost two weeks went by without a clear, sunny day. But then, looking at the data, they realized they had learned something from the cloudy weather: the modules performed much better than conventional flat panels under such conditions.

Cloudy or not, the vertical modules outperform fixed flat panels mainly because the 3-D structures’ vertical surfaces can collect much more sunlight during mornings, evenings, and winters, when the sun is closer to the horizon.

The 3-D modules cost more than ordinary flat panels because they use more photovoltaic cells for a given footprint. But the higher cost is partially balanced by a much higher and more uniform energy output.

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