The University of Massachusetts Amherst
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Team of Chemists and Electrical Engineers Outline New Way to Harvest Heat Energy to Produce Electricity

Zlatan Aksamija

Zlatan Aksamija

Assistant Professor Zlatan Aksamija of the Electrical and Computer Engineering Department was part of the UMass team of chemists and electrical engineers who outlined a new way to advance a more efficient, cheaper, polymer-based harvest of heat energy to produce electricity. Aksamija and chemist Dhandapani Venkataraman reported their findings this month in Nature Communications.

“By one official estimate, American manufacturing, transportation, residential, and commercial consumers use only about 40 percent of the energy they draw on, wasting 60 percent,” explained the News Office release. “Very often, this wasted energy escapes as heat, or thermal energy, from inefficient technology that fails to harvest that potential power.”

To address this vast loss of energy, Venkataraman and his chemistry Ph.D. student Connor Boyle worked with Aksamija and his electrical engineering Ph.D. student Meenakshi Upadhyaya in a very productive collaboration.

As Aksamija explained, “Using polymers to convert thermal energy to electricity by harvesting waste heat has seen an uptick in interest in recent years. Waste heat represents both a problem but also a resource; the more heat your process wastes, the less efficient it is.” He added that harvesting waste heat is less difficult when there is a local, high-temperature gradient source to work with, one such as a power plant.

Thermo-electric polymers are less efficient at heat harvesting compared to rigid, expensive-to-produce inorganic methods that are nevertheless quite efficient, Aksamija said in the News Office article, but polymers are worth pursuing because they are cheaper to produce and can be coated on flexible materials – to wrap around a power plant’s exhaust stack, for example.

Recently, scientists have been addressing this issue with a process called “doping.” With it, researchers mix chemical or other components into polymers to improve their ability to move electric charges and boost efficiency.

But doping involves a tradeoff, Aksamija said. It can either achieve more current and less thermally-induced voltage, or more voltage and less current, but not both. “If you improve one property, you make the other worse,” he explained, “and it can take a lot of effort to decide the best balance,” or optimal doping.

In their collaborative research on this issue, the chemists conducted experiments, while the engineering team performed efficiency analyses along the curve from “zero doping” to “maximum doping” to identify the best balance for many different materials. For the massive number of simulations they ran to test hundreds of scenarios, they used the Massachusetts Green High Performance Computing Center in nearby Holyoke.

The News Office article provides additional details of the innovative research, but the researchers said they hope their findings should provide a new path for designing more efficient polymers for thermo-electric devices, and they hope their paper provides a basis to move polymer-based thermo-electrics forward. (July 2019)