The companies that turn heat into electricity usually try to harvest their heat in hot environments, like under the hood of a vehicle or on the outside surface of a steam pipe.

Researchers at MIT have come up with an experimental device that could take heat directly from the sun.

A group of researchers led by professor Gang Chen have devised a thermoelectric device that convertssolarheat directly into power via the Seebeck effect. In the Seebeck effect, a sharp temperature gradient can result in an electric charge. (Solar thermal power plants work indirectly: heat makes steam and then turns a turbine.). The device is only 7 percent to 8 percent efficient and requires a difference in temperature of around 200 degrees Celsius, but it's more efficient than other, similar experimental devices. (See more in the Nature article.)

The device consists of a thermoelectric converter in a vacuum tube that sits atop a copper plate. The copper gets hot and whammo.

Conceivably, a device like this could be placed on roofs or under solar panels to generate power.

You probably didn't know this, but you live in the Golden Age of Waste Heat. The bulk of energy consumed in this country is actually dissipated as heat: think of how hot it gets under the hood of a car or in a factory. Traditional vendors such as Recycled Energy Development (RED) use mechanical systems to make use of this energy source. A new wave of companies, such as Alphabet Energy out of UC Berkeley, Phononic Devices or GMZ Energy, which Chen founded, have developed semiconductors that can convert heat directly to power. Conversely, Promethean Power converts electricity from solar panels to thermal energy to run refrigerators in India.

Interestingly, Chen's new device relies on bismuth telluride, which some say isn't as efficient as other materials. Alphabet relies on silicon nanowires.