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Heat from car exhaust could improve mileage

GM and BMW plan to test devices that convert heat from a car's engine into usable electricity next year. Researchers are trying to develop more efficient materials.

Researchers are trying to find a useful outlet for cars' waste heat--namely their electrical load.

General Motors and BMW plan to test devices that will convert excess heat from a car's motor into electricity next year, according to an Associated Press report Sunday.

GM has built a prototype, a metal-plated device that will fit around an exhaust pipe. Researchers told AP that they expect that it could improve fuel efficiency in a Chevrolet Suburban by about 5 percent, or 1 mile per gallon. The improvements would be greater in smaller, more fuel-efficient vehicles.

Auto companies are working with thermoelectrics researchers at Ohio State University to improve the efficiency of existing materials by producing an electric current from differences in temperature.

Researchers estimate that 30 percent to 40 percent of the heat generated from a car's engine is used. The rest is lost through exhaust or engine cooling.

Thermoelectric devices are already used in space exploration and in more commonplace applications, such as like cooling car seats. But research in the area, some of which was abandoned decades ago, is perking up as businesses explore new energy efficiency technologies.

Researchers at Pennsylvania State University on Friday said they have developed a polymer material they hope can be used to cool computers or refrigerators. These specially designed plastics would go into solid-state refrigerators that eliminate the use ozone-damaging freon in traditional power-hungry refrigerators.

A commercially available thermoelectric module connected to a solar panel. When current goes through the device, one side heats up, while the other cools. Researchers are developing more efficient materials. Martin LaMonica/CNET News

Besides automakers, a couple of other companies are trying to commercialize thermoelectric technology.

Promethean Power is developing a solar-powered refrigerator that will use a thermoelectric module for cooling.

Another company, GMZ Energy, earlier this year received seed funding from Kleiner Perkins Caufield & Byers to develop thermoelectric materials using nanotechnology for refrigeration, air conditioning, waste heat recovery, and solar thermoelectrics.