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New thermocell technique could harvest power from waste heat at power plants

When you drive past a power plant, you may see steam billowing out of its tall stacks. The steam comes from heat generated during the power production process.

Lost heat can be thought of as lost energy, and researchers are always looking for ways to instead recycle it into more electricity production. One setup, known as a thermocell, keeps one side of a device cold while the other side is exposed to the heat source. The electricity that begins to flow from the hot to cold sides can then be harvested.

Researchers at Monash University in Australia have created a new type of thermocell that is the most efficient yet. It has no carbon emissions and is particularly good at operating from 212 to 392 degrees Fahrenheit — key temperatures for waste heat at facilities like power plants. Their thermocell uses steam to create electricity by exposing one side to the hot steam and the other to cool air or water.

“The major benefit of a thermocell is that it harnesses energy that is already readily out there; you’re just harnessing energy that is otherwise lost to surroundings,” PhD student Theodore Abraham said.

More traditional thermocells contain water, which boils off at those temperatures. The Monash researchers used a liquid packed with electrolytes, which give it a higher boiling point than water.

Thermocells can be used anywhere there is heat, which means they could run off of a car’s tail pipe or even a volcano. They can also run off the human body; one of the finalists at the Google Science Fair this year developed a hand-heat-powered flashlight.

Thermocells are not more common because they are not efficient or inexpensive enough to compete with more common energy sources. It is cheaper to just let waste energy escape into the air or channel it into a steam power plant, where it is used to turn a turbine that generates energy. The Monash researcher’s improvement is a good step toward changing that.

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