Energy | Ecotrope

A secret to reusing waste heat: Your microwave

Ecotrope | Sept. 20, 2011 3:51 a.m. | Updated: Feb. 19, 2013 1:35 p.m.

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You still shouldn't put metal in your microwave ... but the concept worked out pretty well for chemists at Oregon State University.

You still shouldn't put metal in your microwave … but the concept worked out pretty well for chemists at Oregon State University.

In the time it takes you to reheat yesterday’s pizza, microwave energy can be used to create compounds that capture wasted heat from cars, machines and industry and turn it into electricity.

Oregon State University chemists have discovered that simple microwave energy can reduce an expensive three-day process to two minutes. The findings could make it a whole lot easier (and cheaper) to reuse the huge portion of energy from cars, machines and industry around the world that is lost as waste heat.

For the same reason you’re not supposed to put metal into the microwave, the chemists used microwaves to heat powdered metals to 1,800 degrees to produce heat-capturing compounds called “skutterudites.” It took just a few minutes, and the results could be huge.

From OSU:

“Thermoelectric power generation, researchers say, is a way to produce electricity from waste heat – something as basic as the hot exhaust from an automobile, or the wasted heat given off by a whirring machine. It’s been known of for decades but never really used other than in niche applications, because it’s too inefficient, costly and sometimes the materials needed are toxic. NASA has used some expensive and high-tech thermoelectric generators to produce electricity in outer space.

A hybrid automobile that has both gasoline and electric engines, for instance, would be ideal to take advantage of thermoelectric generation to increase its efficiency. Heat that is now being wasted in the exhaust or vented by the radiator could instead be used to help power the car. Factories could become much more energy efficient, electric utilities could recapture energy from heat that’s now going up a smokestack. Minor applications might even include a wrist watch operated by body heat.

“To address this, we need materials that are low cost, non-toxic and stable, and highly efficient at converting low-grade waste heat into electricity,” Subramanian said. “In material science, that’s almost like being a glass and a metal at the same time. It just isn’t easy.  Because of these obstacles almost nothing has been done commercially in large scale thermoelectric power generation.”

Skutterudites have some of the needed properties, researchers say, but historically have been slow and difficult to make. The new findings cut that production time from days to minutes, and should not only speed research on these compounds but ultimately provide a more affordable way to produce them on a mass commercial scale.”

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