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'Green machine' makes power from waste heat

Thermoelectricity in action: ElectraTherm squeezes 50 kilowatts of electricity out of industrial waste heat.

Thermoelectricity--the practice of drawing electricity from heat--is getting a real-life work-out.

ElectraTherm on Thursday said that it has installed a 50-kilowatt machine that uses industrial waste heat as its "fuel."

A 50 kilowatt 'green machine' that runs on waste heat. ElectraTherm

The company says that the ElectraTherm Green Machine, installed at Southern Methodist University in Dallas, will recoup its purchase cost in three to four years with electricity costing three or four cents per kilowatt-hour during that time.

The machine uses an organic Rankine cycle to heat liquids which are turned into a vapor that turns a turbine to make electricity.

The thermoelectric effect has been known since the early 19th century. But the idea of making electricity from heat appears to be getting more attention.

Kleiner Perkins Caufield & Byers earlier this year funded an spin-off from the Massachusetts Institute of Technolocy called GMZ Energy.

ElectraTherm says that its unit doesn't require any specialized electronics and is relatively easy to maintain. The basic technology can be scaled up to produce up to 500 kilowatts.

For comparison, a typical home solar installation can generate between two and four kilowatts, while Google's solar array at its corporate headquarters--considered the largest in the U.S.--is 1.6 megawatts.

Preston Koerner in the Jetson Green green-building blog said the ElectraTherm machine demonstrates that heat-to-electricity can be done at a relatively small scale. It generates about enough electricity for about 40 homes, he added.