Substances that convert heat to electric energy are discovered with efficiency five times higher than conventional

byOmar Bárcena

If you can efficiently convert thermal energy generated by the operation of a power plant or machine into electric energy, you can expect a large increase in energy efficiency. Many researchers have been conducting research on materials capable of highly efficient power generation, but MIT scientists and others are able to obtain high energy by applying high heat to specific materials under high magnetic field I suggested theoretically.

Large, nonsaturating thermopower in a quantizing magnetic field | Science Advances
http://advances.sciencemag.org/content/4/5/eaat2621

New materials, heated under high magnetic fields, can produce record levels of energy
https://knowridge.com/2018/05/new-materials-heated-under-high-magnetic-fields-could-produce-record-levels-of-energy/

Thermoelectric power generationMeans that the temperature difference of the object is directly converted into electric powerSeebeck effectIt is a power generation method which obtains electric energy from the object with heat by utilizing the phenomenon called "power generation". In this system where electric potential can be generated by generating a potential difference between the two surfaces when one surface of the object is in a high temperature state and the other surface is in a low temperature state, a material capable of efficiently converting heat to electric energyThermoelectric conversion element) Is required. Researchers around the world have been searching for efficient thermoelectric conversion elements for 60 years since the practical application of thermoelectric power generation has been accepted with reality.

Meanwhile, according to research results published by MIT's research team on Science Advances of the scientific journal on May 25, 2018, a thermoelectric conversion element capable of generating power at a rate five times higher than that of a conventional thermoelectric conversion element was discovered It was said that it was done.

The thermoelectric conversion element joins two kinds of different metals and semiconductors, generates a temperature difference at both ends, moves the high temperature side electrons to the low temperature side, and generates a voltage. In most materials, electrons can only exist in a certain range (band), and when electrons moveBand gapIt is necessary to jump over the area that can not exist electrons called.

Being a researcher at MITBrian SkinnerWith Mr.Liang · FuMr,Topological semi-metalWe investigated the nature of a special group of substances without a band gap called as.

byMatthieu Y

Since the band gap does not exist in the topological metal, electrons on the high temperature side can easily move to the cold side. Topological metalloids made artificially in the laboratory move within the material while the movement of electrons is simpleFree electron, It was thought that there was no large thermoelectric potential.

Mr. Skinner and Mr. Hu are interested in "what kind of characteristics of topological metalloids are exposed in the state of being subjected to a strong magnetic field", the theory of the thermoelectric performance of topological metalloids while changing the temperature and the magnetic field I did the work to make it. Then, it turned out that the topological semimetal which is a compound of lead · tin · selenium has thermoelectric performance greatly exceeding the conventional thermoelectric conversion element.

The topological metalloid consisting of lead, tin and selenium is about 30TeslaThe research team calculated that "ZT" which is the evaluation unit of the thermoelectric conversion element has a high value of 10 under a strong magnetic field environment (general MRI operates at about 2 to 3 Tesla). ZT = 2 even for the thermoelectric conversion element which was considered to be the most efficient so far, Skriner and others have discovered material having thermoelectric conversion efficiency five times more than before.

byBrian Jeffery Beggerly

When the topological metalloid composed of lead, tin and selenium is exposed to a magnetic field, in addition to the movement of electrons from the hot side to the cold side, "the same behavior as an electron with a positively chargedHoleWill move from the cold side to the hot side. Because heat is converted to electric power by the function of electrons and holes, "In principle, voltage can be obtained only by strengthening the magnetic field," Skinner says.

Unfortunately, a very strong magnetic field of 30 Tesla can only be created in a special laboratory environment, and in order to maintain conversion efficiency, topological metalloids are required to have high purity. Skinner said that "There is a high possibility that even better materials are available besides the topological metal that we have experimented this time," he says, and it is said that more efficient materials will be found. In addition, the research team said that he will advance research so that it can have high thermoelectric conversion efficiency under the magnetic field which can be generated comparatively easily on the order of 3 Tesla.