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

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

An international team of scientists has discovered how to capture the heat and turn it into electricity.

The discovery, published last week in the newspaper Progress of science, could generate more efficient energy production from heat, for example in car exhaust gases, interplanetary space probes and industrial processes.

"With this discovery, we should be able to produce more electrical energy with heat than today," said Joseph Heremans, co-author of the study, professor in mechanical and aerospace engineering and distinguished researcher in nanotechnology from Ohio to Ohio State University. "It's something no one thought possible up to now."

The discovery is based on tiny particles called paramagnons, bits that are not quite magnets, but carry a 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, which, until this discovery, could not be used to collect water. 39, energy at room temperature.

"Conventional wisdom once was that if you have a parameter and you warm it up, nothing happens," said Heremans. "And we found that it is not true. What we have found is a new way of designing thermoelectric semiconductors, materials that convert heat into electricity. The conventional thermoelectrics we have over the last 20 years are too inefficient and give us too little energy, so they are not really used on a large scale. It changes that understanding.

Magnets play a crucial role in the collection of thermal energy: when one side of a magnet is heated, the other, the cold side, becomes more magnetic and produces a rotation that pushes the electrons into the magnet and creates electricity.

The paradox, however, is that when the magnets are heated, they lose most of their magnetic properties, turning them into paramagnets – "magnets almost but not quite" – called them Heremans. This means that until this discovery, no one had thought of using paramagnetics to recover heat because scientists thought that paramagnetics were not able to collect energy.

The research team, however, found that paramagnons only grow electrons for one billionth of a millionth of a second, which is enough to make paramagnetics that collect energy viable.

The research team – an international group of scientists from the state of Ohio, North Carolina State University and the Chinese Academy of Sciences (both authors in this review article) – began testing paramagnons to see if, in good circumstances, they would produce the same results. spin needed.

Heremans explained that what they discovered, is that paramagnons actually produce the type of spin that drives electrons.

And that, he said, could help to collect energy.

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Yuanhua Zheng, a graduate student from the state of Ohio, is also an 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 Scientific Research Bureau and the US Department of Energy. energy.

Reference: "Paramagnon Trainer in Li-doped Thermoelectric Merit MnTe" by Y. Zheng, T. Lu, Mr. MH Polash, Mr. Rasoulianboroujeni, N. Liu, ME Manley, Y. Deng, Sun PJ, XL Chen2 , RP Hermann, D. Vashaee, JP Heremans and H. Zhao, September 13, 2019, Progress of science.
DOI: 10.1126 / sciadv.aat9461