TECHNOLOGY FOR CHANGE

Thermoelectric Generators Turn Heat into an Asset

R. Colin Johnson | Date: 02-03-11 | Comments

Excess heat remains a major headache for everything from server farms to automobile exhausts, but breakthroughs in solid-state thermoelectric materials aim to turn waste heat into electricity.

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Thermoelectric Generators Turn Heat into an Asset
Recent breakthroughs in the performance of thermoelectric materials boost their efficiency, promising to bring energy harvesting technologies into the mainstream.

Thermoelectric generators are fabricated from solid-state materials that produce electricity from waste heat or vice versa. For instance, those coolers that you plug into the cigarette lighter socket in your car use thermoelectric generators in reverse. In particular, they use electricity from your car battery to transport heat from inside the cooler. However, recent advances in efficiency, spearheaded by Boston College, promise to make commercially feasible thermoelectric generators that convert almost any amount of waste heat into electricity.

Pacific Northwest National Labs (PNNL) aims to harvest natural temperature differences in building ductwork to turn waste heat into electricity.

Thermoelectric materials work by virtue of either the Seebeck effect for transforming heat into electricity or the Peltier effect that transforms electricity to heat. Technically, both effects work on temperature gradients, enabling them to harvest or generate cold, too. Many solid-state materials have the potential to harness these effects; however, most are so inefficient as to not be worth the trouble.

Today thermoelectric applications are made commercially feasible by virtue of their light weight and small size, rather than their high efficiency. For instance, without thermoelectric materials, that cooler plugged into your cigarette lighter socket would require a heavy electric motor to compress greenhouse gases (like your refrigerator at home). However, a wide variety of semiconductor materials are now being specifically engineered to improve their thermoelectric efficiency�called their figure-of-merit (ZT)�heralding a new era where excess heat can be efficiently harvested to generate electricity for a wide variety of applications.

Next: Widespread Use of Thermoelectric Generators Possible >>