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 percent of the energy produced by a typical gasoline engine is used to move a car or power its accessories, and nearly 60 percent 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.
“The material does all the work. It produces electrical power just like conventional heat engines — 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.”
“Thermoelectrics are also very small,” he added. “I like to say that TE converters compare to other heat engines like the transistor compares to the vacuum tube.”
The engineers took a unique strategy to design this new material.