Researchers at Penn State have developed a practical way to harness the energy from curved, hot surfaces and convert it to electricity. Devices known as thermoelectric generators have been around for some time. They use silicon and other compounds to convert heat into a small electric current. These devices have been mounted onto rigid metal plates to draw heat from surfaces.
But in many places, heat is available from other surfaces – like exhaust stacks and pipes. So, the Penn State researchers created a grid of generators with spaces in between that can bend around a pipe. Bending around and conforming to the surface increases the amount of power that can be generated.
The efficiencies of these units is still quite low, typically 5-8% of the heat lost from a surface. But for a manufacturing facility that could have several hundred feet of hot exhaust stacks or heated process fluids needing cooling anyway, this could be worth several kW of electric power – free of charge. Thermoelectrics work best when the surface is hot and the surrounding air cool. Because of the low efficiency, it is not a good idea to put these devices on steam pipes or surfaces that would ordinarily be insulated to keep heat in. But for applications where you have lots of waste heat (like a boiler stack), it could represent a cost effective way to generate power. – Steve Terry, DTC HVAC & Refrigeration Instructor
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