Researchers at Wake Forest University's Center of Nanotechnology and Molecular Materials are working with some interesting stuff. They have developed a cloth-like material made from carbon nanotubes that has thermo-electric properties.
Thermoelectric devices (TEDs) have been around since the 19th century. A TED is created when two dissimilar metals are placed in contact and heated. A potential is developed across the junction and associated wires, and current flows from one metal to the other and through a connected load. This effect and the related cooling effect was discovered and analyzed by the French physicist Jean Charles Athanase Peltier and the German physicist Thomas Johann Seebeck. A TED will work the other way: If a current is forced through the junction, one side gets hotter and the other side gets colder. If you stack up plates of dissimilar materials, you can make a small “heat pump” and cool the CPU in your overheating laptop computer.
Materials used for simple TEDs — like the one in your gas water heater that keeps the valve open as long as the pilot flame remains lit — are made from inexpensive materials like iron and constantan. The Seebeck constant for an iron-constantan junction is about 55uV/deg-C. For the heat pump version, bismuth and telluride works pretty well, but it's a lot more expensive.
At Wake Forest, they've got a type of TED made of carbon nanotubes and plastic fibers that responds to a temperature differential. Since it's small and can be made inexpensively, the hope is that they can make a thermopile that will produce enough power to be practical. They plan to turn what they've developed in the lab into useful, manufacturable products that could recover waste heat in cars and trucks and produce electricity in usable quantities. Or use your body heat to recharge your cellphone battery. Also you could have clothing that keeps you warmer — or cooler — than the ambient temperature as the need dictates. And, of course, there's heating and cooling of buildings.
The research appears in the current issue of Nano Letters, titled “Multilayered Carbon Nanotube/Polymer Composite Based Thermoelectric Fabrics.” Wake Forest is in talks with investors to produce its Power Felt product commercially.