Thermoelectric generators directly convert waste heat into electricity. The Perpetua Power Puck is the first to use a thermoelectric semiconductor on a flexible substrate developed at the U.S. Department of Energy's Pacific Northwest National Laboratory. Because they're flexible, the pucks--which have pins to disperse excess heat--can conform to curved heat-­producing surfaces such as a hot-water pipe or pump. A startup based in Corvallis, OR, is initially marketing the pucks as power sources for wireless sensors at sites such as power plants and dams; affixing the gadget to a surface just 10 ˚C warmer than the surrounding temperature can produce more than five volts and several hundred microwatts of power, enough for a typical wireless sensor. The company will begin shipping products this spring.

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