Free Power for Cars

Automakers look to thermoelectrics to help power tomorrow's vehicles.

Converting heat directly into electricity is nothing new; it has been possible since 1821. But thermoelectric materials have been too inefficient to make them practical for anything but a few niche uses, such as in deep space probes.

Recent advances using nanotechnology, however, have revived this moribund field, and have car makers such as General Motors and BMW taking notice, hoping to increase fuel efficiency and eventually replace alternators and possibly even internal combustion engines with thermoelectric generators.

"I think right now that thermoelectrics have a good chance of succeeding," General Motors senior analyst Francis Stabler reported last week at the Materials Research Society meeting in Boston.

As much as 70 percent of the fuel energy burned up in car engines doesn't go toward moving the vehicle along or powering the CD player, he said. Instead, it's dissipated as waste heat. Stabler says a new generation of thermoelectric materials can convert heat to electricity well enough to be used for taking the burden of electricity generation off the engine, thereby saving fuel.

Researchers still need to find ways to make these materials cheaply and consistently, however, before they can be widely deployed. But certain niche uses could help the technology get established. Already, Amerigon, a Deerborn, MI manufacturer, has sold well over a million car seat heating and cooling units that use an older version of the technology. When electricity is applied to thermoelectrics materials they transfer heat, cooling an area or heating it depending on the direction of the current.

If the next generation of thermoelectric materials can be manufactured inexpensively, they could be used in more demanding applications. Wrapped around a car's exhaust pipe, for instance, they could harvest waste heat to produce electricity. Initially, this electricity might be used to supplement the electricity generated by the vehicle's alternator, making it possible to run more electrical devices without adding more strain to the engine.

If the technology proves to be reliable, Stabler says, it could eventually replace alternators altogether and run electrical water and oil pumps, relieving the extra work for the engine, boosting performance, and saving fuel. John Fairbanks, technology development manager at the U.S. Department of Energy, suggests that if all GM cars alone used this technology, it would save roughly 100 million gallons of gas per year.