Technology Would Power Cars with Auto Exhaust

Dec. 15, 2010

Developed by GM and Purdue University, system harvests heat from engine exhaust to generate electricity.

What if the very emissions developers are working so feverishly to diminish could be the fuel that powers tomorrow's automobiles?

Purdue University researchers are working with General Motors to create a system that essentially consumes its own exhaust, converting heat from emissions into electricity, thereby improving fuel economy by reducing the engine's workload.

The enabling technology would be next-generation thermoelectric generators, which produce an electric current when a difference between temperatures emerges, enough to charge batteries and power a car's electrical systems. In January, the team will begin testing a prototype behind a car's catalytic converter, where it will consume heat from exhaust gases that can approach 1,300 degrees.

Researchers are hoping the initial prototype will reduce the vehicle's fuel consumption by 5%, while more advanced systems that work at higher temperatures could make sharper reductions of 10% in the future, according to Purdue engineering professor Xianfan Xu.

Purdue mechanical engineering doctoral student Yaguo Wang works with a high-speed laser at the Birck Nanotechnology Center to study thermoelectric generators. The devices harvest heat from an engine's exhaust to generate electricity, which could reduce a car's fuel consumption.The technology is contingent on unique metals that can withstand a massive differential in temperature, where one side facing hot gases stays hot, while the other side must stay cool. "The material is hot on the side facing the exhaust gases and cool on the other side, and this difference must be maintained to continually generate a current," said Xu, who is leading the research and has been collaborating with General Motors on thermoelectric research for nearly a decade.

Researchers at GM are using a thermoelectric material called skutterudite, a mineral made of cobalt, arsenide, nickel or iron that is mixed with rare-earth elements, such as lanthanum, caesium, neodymium and erbium to reduce the thermal conductivity of the skutterudite.

The work is being funded with $1.4 million from the National Science Foundation and the Department of Energy.

Thermoelectric technology wouldn't just be limited to solving challenges with cars. Xu says it could also be used to harness waste heat in homes and power manufacturing facilities.