Recycling waste heat into energy: researchers take a step toward more efficient conversion

The right material wrapped around your car's exhaust system could one day scavenge heat that would otherwise be wasted, turning it into energy to warm the cabin or recharge the battery.

Engineers and physicists at the University of Michigan have taken a step toward improving the efficiency of a promising candidate for this burgeoning power source.

The researchers studied skutterudites, a class of mechanically strong thermoelectric materials that, when combined with certain elements such as the metal barium, has the right mix of properties to effectively make this energy conversion: The material conducts electricity well, and conducts heat poorly. The researchers identified certain configurations of the atoms in the compound that drastically increase the materials' efficiency.

Their work is published in the current edition of Physical Review Letters.

"We knew that skutterudites are promising materials. But we did not know what features we could manipulate to maximize the conversion of heat into electricity," said Ctirad Uher (pronounced STEERad YOUher), professor in the Department of Physics. "In this paper, we propose that certain configurations of the filler element barium will be very effective in lowering the materials' thermal conductivity and thus increasing their conversion efficiency.

"This is an important advancement in the sense that it provides guidance for the experimentalists to focus as they try to synthesize highly efficient thermoelectric materials."