Bloomberg News

Hot Nanotubes Helping Solar Panels Capture More Sunlight

January 19, 2014

Carbon Nanotubes

Scanning electron micrograph (SEM) of carbon nanotubes. Photographer: Dennis Kunkel Microscopy, Inc./Visuals Unlimited/Corbis

Researchers at the Massachusetts Institute of Technology are seeking to increase the efficiency of solar cells by helping them take advantage of more of the sun’s rays.

MIT scientists are testing solar cells with a layer of carbon nanotubes that “make it possible to take advantage of wavelengths of light that ordinarily go to waste,” according to a statement yesterday from the Cambridge, Massachusetts-based university.

Standard polysilicon photovoltaic cells don’t “respond” to the entire spectrum of sunlight, limiting the amount of photons they’re able to convert into electricity. Scientists have said standard polysilicon has a theoretical maximum efficiency of 33.7 percent. The nanotube technology may be used to surpass that limit, according to Evelyn Wang, an MIT associate professor of mechanical engineering.

Cell efficiency, the amount of energy in sunlight that’s converted into electricity, “could ideally be over 80 percent,” she said in the statement.

MIT scientists combined carbon nanotubes, hollow cylinders with walls that are one-atom thick, with photonic crystals to create an “absorber-emitter.” When the nanotubes absorb concentrated sunlight, their temperature rises, heating the device to as much as 962 degrees Celsius (1,763 degrees Fahrenheit).

Just as a red-hot iron glows in a fire, the heated crystals emit light that the photovoltaic cell is able to turn into electricity, according to the statement.

The most efficient standard cells in production today convert about 22 percent of sunlight energy into electricity.

To contact the reporter on this story: Christopher Martin in New York at cmartin11@bloomberg.net

To contact the editor responsible for this story: Reed Landberg at landberg@bloomberg.net


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