By now, most of us know the term photovoltaic—solar radiation converting sunlight into electricity—but there’s a new term we might need to become familiar with: thermoelectric, the process of directly converting heat from the sun, or other sources, into electricity.

A team of researchers at Boston College and the Massachusetts Institute of Technology (MIT) are creating high-efficiency solar thermoelectric devices, which convert the sun’s heat into electricity.

Thermoelectric sounds like another solar technology that’s increasingly gaining popularity—solar thermal—but it’s different. Solar thermal projects concentrate sunlight on a fixed point and uses a medium to move the stored heat energy to a place where it can be converted into electricity by superheating water into steam and using the steam to turn a turbine that generates electricity—ultimately the same process that natural gas and coal-fired power plants use to generate electricity.

But the thermoelectric method converts sunlight directly into electricity, without needing a secondary thermal conductor.

The device won’t be on your rooftop tomorrow, but the research is promising, producing a device that could both provide electricity and hot water for homes, residences and more, according to the researchers.

The team used nanomaterials and an optical concentrator to focus sunlight on the device, and they coupled it with a hot-water heater to cool the thermoelectric aspect of the device to keep it producing electricity efficiently.

The team of MIT and Boston College researchers have developed a device that converts solar thermal heat into electricity at a higher efficiency rate than previously possible—and also heats water.

“We first collect the Sun's radiation and convert it into heat, and immediately convert the heat into electricity via thermoelectric materials,” said Boston College Professor of Physics Zhifeng Ren. “For efficient electricity conversion using thermoelectric materials, we need to cool them, that's where the hot water is generated.”

Ren and the team of researchers published their work, “High-performance flat-panel solar thermoelectric generators with high thermal concentration,” in Nature Materials this week.

The device they’ve developed encases a thermoelectric device in a vacuum to increase its efficiency, according to Ren.

“Our electricity generation is 7 to 8 times [higher than] the previous record due to better thermoelectric materials, thermal concentration and operation in vacuum,” he said.

Photovoltaics only provide power from the sun’s visible spectrum of radiation. The thermoelectric devices use the range of the sun’s spectra.

“It captures the whole solar spectra and converts it into heat through the selective surface and then converts the heat into electricity via thermoelectric materials,” he said.