New GM Technology Could Turn Exhaust Heat into Energy

Wouldn’t it be cool if the heat your car’s engine emits could be captured and converted into energy to power your stereo or air conditioning? Well, that day is coming.

Recently, General Motor’s Lightweight Thermal Energy Recovery (LighTER) System received a $2.7 million federal award from the U.S. Department of Energy’s (DOE) recently formed Advanced Research Program Agency – Energy (ARPA-E).

Headquartered in Warren, Michigan, General Motors (GM) will use the funds to develop a shape memory alloy (SMA) energy recovery device that will convert waste heat from car engines into electricity. Such devices will both increase fuel efficiency by as much as 10% and provide power to the car’s individual components. Captured heat could even power a hybrid battery or replace a car’s alternator.

SMA heat engine technology depends on a scientific curiosity. “When you heat up a stretched SMA wire, it shrinks back to its pre-stretched length, and when it cools back down it becomes less stiff and can revert to the original shape” said Jan Aase, director of GM’s Vehicle Development Research Laboratory. “A loop of this wire could be used to drive an electric generator to charge a battery.”

“No one else anywhere in the world is doing this work as far as we know,” Aase said. “In a hybrid system, the electrical energy could be used to charge the battery. In a conventional engine, this could perhaps even replace the alternator without any load on the engine.”

The award from ARPA-E was the only grant to an automaker among $151 million the agency will distribute. GM will work with HRL Laboratories; Dynalloy, Inc., and the Smart Materials Collaborative Research Lab at the University of Michigan. Over the next two years, GM and its partners will work to create a working prototype.

"This award is significant for the gains in energy efficiency it could bring, and because it signifies how GM is doing business though collaboration and partnership,” said Alan Taub, GM vice president of global R&D.

The idea of an SMA heat engine “has been around for 30 years,” Aase said, “but the few devices that have been built were too large and too inefficient to make it worthwhile.”