About 40 percent of the energy from gasoline or diesel fuel is wasted as exhaust heat. If you can convert some of that heat to electricity, it can provide electric power for automotive accessories, relieving some of the burden from the engine resulting in better fuel economy. The device that performs this conversion is a thermoelectric generator and GM has been working on developing one to either assist or even replace the vehicle's alternator.
Installed on a Chevy Suburban, it could improve mileage by 5 percent, on a smaller car, even more. The goal is to increase mileage by 10 percent which, according to GM, could save 100 million gallons of fuel per year in GM vehicles in the U.S. alone. Another great feature is they don't wear out, there are no moving parts. NASA has been using similar technology for 30 years.
GM prototypes are due to be tested next year and estimates are that thermoelectric generators could be ready for production in about 3 years.
GM is not alone in the field, a BMW supplier is working on thermoelectricity with Ohio State University and BSST, a subsidiary of thermoelectrics supplier Amerigon Inc. is working with Ford Motor Co. to develop climate control systems based on thermoelectrics.