Team finds new source of green electricity

Posted by Emma Woollacott

University of Minnesota engineers say they've discovered a completely new way of generating electricity.

They've discovered a new alloy material that converts heat directly into electricity, and which could be used to generate environmentally friendly electricity from waste heat sources.

It could, for example, be used to capture waste heat from a car's exhaust to help charge the battery in a hybrid car. Other possible uses include capturing rejected heat from industrial and power plants or exploiting temperature differences in the ocean to generate electricity.

"This research is very promising because it presents an entirely new method for energy conversion that's never been done before," says  aerospace engineering and mechanics professor Richard James.

"It's also the ultimate 'green' way to create electricity because it uses waste heat to create electricity with no carbon dioxide."

To create the material, the research team combined elements at the atomic level to create a new multiferroic alloy, Ni45Co5Mn40Sn10, with unusual elastic, magnetic and electric properties.

Ni45Co5Mn40Sn10 undergoes a highly reversible phase transformation where one solid turns into another solid, and during this it shows changes in its magnetic properties that are exploited in the energy conversion device.

The material begins as a non-magnetic material, then suddenly becomes strongly magnetic when the temperature is raised a small amount. When this happens, the material absorbs heat and spontaneously produces electricity in a surrounding coil.

"This research crosses all boundaries of science and engineering," says James. "It includes engineering, physics, materials, chemistry, mathematics and more."

The team is now working to create a thin film of the material that could be used, for example, to convert some of the waste heat from computers into electricity.