Powering Your Car with Waste Heat

Technology Review
May 25, 2011

At least two-thirds of the energy in gasoline used in cars and trucks is wasted as heat. Thermoelectrics, semiconductor materials that convert heat into electricity, could capture this waste heat, reducing the fuel needs of the vehicle and improving fuel economy by at least 5 percent. But the low efficiency and high cost of existing thermoelectric materials has kept such devices from becoming practical in vehicles.

Now researchers are assembling the first prototype thermoelectric generators for tests in commercial cars and SUVs. The devices are a culmination of several advances made independently at thermoelectric device-maker BSST in Irwindale, California, and at General Motors Global R&D in Warren, Michigan. Both companies plan to install and test their prototypes by the end of the summer—BSST in BMW and Ford cars, and GM in a Chevrolet SUV.

BSST is using new materials. Bismuth telluride, a common thermoelectric, contains expensive tellurium and works at temperatures of only up to 250 °C, whereas thermoelectric generators can reach 500 °C. So BSST is using another family of thermoelectrics—blends of hafnium and zirconium—that work well at high temperatures. This has increased the generator efficiency by about 40 percent.
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