Researchers have long been working on finding a way to benefit from temperature differences to produce electricity. And now, a group of scientists from Penn State and the National Renewable Energy Laboratory have developed a new flexible thermoelectric generator that can convert wasted heat into electricity by wrapping around hot surfaces like exhaust pipes.  

“A large amount of heat from the energy we consume is essentially being thrown away, often dispersed right into the atmosphere. We haven’t had cost-effective ways with conformal shapes to trap and convert that heat to useable energy. This research opens that door,” Shashank Priya, associate vice president for research and professor of materials science and engineering at Penn State, said.

These flexible devices, however, are immensely compatible with waste heat sources such as pipes in industrial and residential buildings or exhaust pipes on vehicles. Additionally, they do not even have to be glued on surfaces, unlike the previous rigid devices, and as a result, these qualifications highlight the efficiency of the flexible device.

When the thermoelectric generator is placed near a heat source, it produces an electric current through electrons moving from the hot side to the cold side. The device has a flat, square shape and consists of small two-leg couples of strings that are connected to each other. Between the strips, there are gaps providing the flexibility to fit around curved surfaces like pipes. The gaps also maintain the device's flexibility to alter the fill factor, which can be used to optimize thermoelectric devices for different heat sources.

Based on the reports of the scientists, the device successfully completed its testing stage by providing a 150 percent higher power density than other state-of-the-art units. On the other hand, a scaled-up version, which was slightly over 3-inches squared, maintained a power density advantage of 115 percent. According to the researchers, this version produced a total power output of 56.6 watts when placed on the heated surface. “Think about an industrial power plant with pipes hundreds of feet long. If you can wrap these devices around an area that large, you could generate kilowatts of energy from wasted heat that’s normally just being thrown away. You could convert discarded heat into something useful,” Priya added.

Of course, the design comes with advantages. For one, it provides convenience in utilizing the normally wasted heat efficiently. And secondly, it is remarkable that its structure makes the device compatible with difficult-to-apply surfaces such as pipes. Therefore this innovation is promising for generating electricity from areas that were previously difficult to make use of.

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