Renewable energy is a huge area of research for scientists considering the current tenuous state of the world’s environment, which is largely due to its reliance on fossil fuels. One area that seems full of potential is waste heat, or energy dissipated from industry, transportation, commercial buildings, and the like.

Now a team at the University of Massachusetts Amherst have made a breakthrough in research to generate energy from waste heat using a common material that isn’t usually electrically conductive—polymer.

Chemist Dhandapani Venkataraman and electrical engineer Zlatan Aksamija have discovered a key variable to making polymer materials conductive—by observing a new characteristic during doping, a process that adds molecules or removes or adds electrons to the polymers to make them conductive.

“As we increase the doping, we can increase its conductivity but decrease the thermally-induced voltage,” Venkataraman explained to Design News about the discovery. “If we decrease the doping, we decrease the conductivity but increase the thermally-induced voltage. We need to balance both.”

What researchers specifically discovered is that dopants can clump, or cluster--or not, he told us. This is key to achieving the right balance for conductivity. “We found that this clustering is an important new variable that we can tune to achieve the balance,” Venkataraman told Design News.

Aksamija already had led previous research to create polymer-based materials to store solar energy in chemicals bonds and release them as heat on-demand, Venkataraman told us. So there was a precedent for the current work, he said.

“The natural next step is for us to convert this heat to electricity,” Venkataraman told Design News. “Therefore, we started looking into polymer-based thermoelectric materials. We are also intrigued by some experimental results we got in our lab. So we joined hands to look into this problem of converting waste heat into energy.”

Solving the Doping Puzzle

Doping typically involves a trade-off, researchers said. It can either achieve more current and less thermally induced voltage, or more voltage and less current; however, it can’t achieve both. Usually, if researchers improve one property, the other becomes worse, making it difficult to achieve the balance in materials, researchers said.

To achieve their goal with this research, the team conducted experiments and efficiency analyses that ranged from zero doping to maximum doping to come up with the best electrically conductive balance for their polymers.

Researchers published a paper on their work in the journal Nature Communications.

Venkataraman said that the result will likely be a surprise for other scientists in the field, and a significant one, as polymers are useful materials to investigate for generating energy from waste heat for a couple of reasons.

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“The first one is practical,” he told Design News. “Devices made from polymers are lightweight, flexible, low-cost and can be fabricated using solution-based techniques. The second is scientific. Polymers typically have low thermal conductivity, which is essential to achieve high energy conversion efficiency.”

Researchers will continue to work on new designs of polymers for the efficient conversion of waste heat to electrical energy, which they also hope to inspire other scientists also to design, Venkataraman told us.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.