Physics changes heat directly to electricity

Researchers have invented a new material that will make cars even more efficient by converting heat wasted through engine exhaust into electricity.

Science reported the same technology could work in power generators and heat pumps, said project leader Joseph Heremans, Ohio Eminent Scholar in Nanotechnology at Ohio State University.

Scientists call such materials thermoelectric materials, and they rate the materials’ efficiency based on how much heat they can convert into electricity at a given temperature.

Previously, the most efficient material used commercially in thermoelectric power generators was an alloy called sodium-doped lead telluride, which had a rating of 0.71. The new material, thallium-doped lead telluride, has a rating of 1.5—more than twice that of the previous leader.

What’s more important to Heremans is the new material is most effective between 450 and 950°F—a typical temperature range for power systems such as automobile engines.

Some experts argue only about 25% of the energy produced by a typical gasoline engine moves a car or powers its accessories, and nearly 60% is lost through waste heat, which escapes in engine exhaust.

A thermoelectric device can capture some of that waste heat.

“The material does all the work. It produces electrical power just like conventional steam engines, gas, or diesel engines that are coupled to electrical generators, but it uses electrons as the working fluids instead of water or gases, and makes electricity directly,” Heremans said.

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