Researchers find superior way to harness waste heat

London, Nov 20 ( More than half the energy consumed worldwide is wasted, most of it in the form of excess heat.

A new technology, developed by MIT researchers, would help convert this heat — given off by devices ranging from computer chips to car engines — into electricity with an efficiency many times greater than existing devices.

That kind of waste-energy harvesting might, for example, lead to cellphones with double the talk time, laptop computers that can operate twice as long before needing to be plugged in.

Theory says that conversion of heat into electricity can never exceed a specific value called the Carnot Limit, based on a 19th-century formula for determining the maximum efficiency that any device can achieve in converting heat into work.

But current commercial thermoelectric devices only achieve about one-tenth of that limit, says Peter Hagelstein, MIT associate professor of electrical engineering, an MIT release said.

In experiments involving a different new technology, thermal diodes, Hagelstein worked with Yan Kucherov, a consultant for the Naval Research Lab, and coworkers to demonstrate efficiency as high as 40 percent of the Carnot Limit.

The calculations show that this new kind of system could ultimately reach as much as 90 percent of that ceiling, or nine times as much as current devices.