There are solar panels that generate electricity and those that absorb heat for hot water. And now researchers at MIT and elsewhere say they've made progress on using the sun's heat to make electricity.

In a paper published in Nature, the researchers describe the progress they've made on a nanostructured material that improves on the heat-to-electricity conversion rate over existing thermoelectric devices.

MIT professor Gang Chen and doctoral student Daniel Kraemer (right) show a prototype of a solar thermoelectric generator.

The researchers envision that this solid-state material could be packaged either as a stand-alone thermoelectric generator or added onto existing solar hot water systems to make electricity. "Our work opens up a promising new approach which has the potential to achieve cost-effective conversion of solar energy into electricity," the researchers said in their paper.

Massachusetts Institute of Technology professor Gang Chen said a thermoelectric generator in the shape of a flat plate could be placed inside a glass vacuum tube and covered with a black plate of copper to absorb heat. The other side of the thermoelectric device is exposed to the ambient air, creating a temperature difference on the two sides of the plate, which will induce a flow of electricity.

Thermoelectric devices made of different materials are already used for different applications, such as portable coolers or to cool off car seats. But there are a number of researchers and companies seeking to improve the heat-to-electricity conversion efficiency to open up thermoelectric devices to more applications, such as using waste heat from car exhaust systems to power auto electronics.

In their paper, the researchers said they have achieved 4.6 percent peak efficiency, which is seven to eight times better than previous results with solar thermoelectric generators.

If the research, which is funded by the Department of Energy, pays off, it could reduce the cost of solar power significantly and enter the market by piggybacking on the existing solar hot water industry. "It can be a game-changing thing," Chen said in a statement.