New material may help autos turn waste heat into electricity

29 July 2008

Ohio state university researchers have invented a new material that will make cars even more efficient, by converting heat wasted through engine exhaust into electricity.

Ohio state university researchers have invented a new material that will make cars even more efficient, by converting heat wasted through engine exhaust into electricity. In the current issue of the journal Science, they describe a material with twice the efficiency of anything currently on the market.

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 that the new material is most effective between 450 and 950 degrees Fahrenheit -- a typical temperature range for power systems such as automobile engines.

Some experts argue that only about 25 per cent of the energy produced by a typical gasoline engine is used to move a car or power its accessories, and nearly 60 per cent is lost through waste heat -- much of which escapes in engine exhaust.

A thermoelectric (TE) device can capture some of that waste heat, Heremans said. It would also make a practical addition to an automobile, because it has no moving parts to wear out or break down.