Solar Cells That Work Without the Sun

What’s the Latest Development?

A new photovoltaic energy-conversion system developed at M.I.T. can be powered solely by heat, generating electricity with no sunlight at all. “The key to this fine-tuned light emission, described in the journal Physical Review A, lies in a material with billions of nanoscale pits etched on its surface. When the material absorbs heat—whether from the sun, a hydrocarbon fuel, a decaying radioisotope or any other source—the pitted surface radiates energy primarily at these carefully chosen wavelengths.”

What’s the Big Idea?

The new photovoltaic cells developed by M.I.T. use the same principles we rely on to turn heat, for example from steam, into electricity. “According to the U.S. Energy Information Administration, 92 percent of all the energy we use involves converting heat into mechanical energy, and then often into electricity—such as using fuel to boil water to turn a turbine, which is attached to a generator. But today’s mechanical systems have relatively low efficiency, and can’t be scaled down to the small sizes needed for devices such as sensors, smartphones or medical monitors.”