Scientists find a more efficient way to turn heat into electrical energy

Researchers have made an important discovery that could facilitate the collection of energy from heat.

Scientists are finding a new way to capture heat that would otherwise have been lost.

An international team of scientists have discovered how to capture heat and transform it into electricity.

The discovery, published last week in the journal Scientists progress, could create more efficient energy production from heat in things like car exhaust, interplanetary space probes, and industrial processes.

“Because of this discovery, we should be able to produce more electrical energy from heat than today,” said study co-author Joseph Heremans, professor of mechanical engineering and aerospace and Ohio Eminent Scholar in Nanotechnology at Ohio State University. “This is something that, until now, no one believed possible.”

The discovery is based on tiny particles called paramagnons, bits that aren’t quite magnets, but carry some magnetic flux. This is important because magnets, when heated, lose their magnetic force and become what is called paramagnetic. A flow of magnetism – what scientists call “spins” – creates a type of energy called magnon-drag thermoelectricity, something that, until this discovery, could not be used to collect energy at temperature. ambient.

“The conventional wisdom once was that if you have a para-magnet and heat it up, nothing happens,” Heremans said. “And we have found that this is not true. What we discovered was a new way to design thermoelectric semiconductors, materials that convert heat into electricity. The conventional thermoelectrics we’ve had over the last 20 years or so are too inefficient and give us too little energy, so they’re not really being used on a large scale. It changes that understanding.

Magnets play a crucial role in collecting energy from heat: when one side of a magnet is heated, the other side (the cold side) becomes more magnetic, producing a spin, which pushes the electrons in the magnet and creates electricity.

The paradox, however, is that when magnets heat up, they lose most of their magnetic properties, turning them into para-magnets – “almost but not quite magnets,” Heremans calls them. This means that, until this discovery, no one had thought of using para-magnets to recover heat because scientists believed that para-magnets were not able to collect energy.

What the research team found, however, is that paramagnons only push electrons for a billionth of a millionth of a second, long enough to make paramagnetics viable energy collectors.

The research team, an international group of scientists from the State of Ohio, North Carolina State University and the Chinese Academy of Sciences (all equal authors on this journal article) – began testing paramagnons to see if they could, under the right circumstances, produce the necessary spin.

What they found, Heremans said, is that paramagnons actually produce the type of spin that pushes electrons.

And that, he said, could help collect energy.

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Ohio State graduate student Yuanhua Zheng is also the author of this work. The research was conducted in partnership with other researchers at the US Department of Energy’s Oak Ridge National Laboratory and was supported by the National Science Foundation, the Air Force Office of Scientific Research and the Department American Energy.

Reference: “Paramagnon drag in high thermoelectric figure of merit MnTe doped with Li” by Y. Zheng, T. Lu, Md MH Polash, M. Rasoulianboroujeni, N. Liu, ME Manley, Y. Deng, PJ Sun, XL Chen2, RP Hermann, D. Vashaee, JP Heremans and H. Zhao, September 13, 2019, Scientists progress.
DOI: 10.1126 / sciadv.aat9461


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