Scientists from the Massachusetts Institute of Technology and the National Renewable Laboratory
Heat engine created by engineers,is a thermophotovoltaic (TVP) cell that captures high-energy photons from an incandescent heat source and converts them into electricity. This system repeats the idea of how solar panels work.
The thermal element developed at MIT consists ofthree main parts. The inner mirror layer of gold is sequentially coated with two layers of alloys, the upper (outer) of which has a high band gap, and the lower (intermediate) one has a slightly smaller width. Band gap - a characteristic of semiconductors and dielectrics, the minimum energy required for the transition of an electron from the valence band to the conduction band.
The outer layer captures photons from the highestenergy and converts it into electricity. The intermediate alloy captures and converts the lower energy light particles that pass through the first layer. Photons that have reached the gold layer are reflected by the mirror surface and returned to the heat source. This approach, according to engineers, reduces energy losses.
The researchers tested the created elementusing a heat flow sensor. The scientists concentrated the light from a high-temperature lamp on their heat engine and tested how the energy efficiency of the element changed depending on the temperature. Measurements showed that at temperatures from 1900°C to 2400°C the efficiency of the developed TVP element was 40%.
Schematic diagram of a thermal battery. Source: Henry et al., MIT, Nature
The engineers plan to turn their elements intothermal battery network scale. Such a system would absorb excess energy from renewable sources such as the sun and store it in highly insulated hot graphite jars. If necessary, for example, on cloudy days, TVP-elements will convert heat into electricity and supply it to the network.
Thermophotovoltaic cells are the latest step towards demonstrating that thermal cells are a viable concept.It is a safe, environmentally friendly technology that can have an impact on reducing carbon dioxide emissions.
Henry Asegun, Professor, MIT Professor and Co-Author of the Study
According to researchers, over 90%electricity in the world is generated from heat sources (coal, gas, nuclear energy). Steam turbines are the traditional way of converting heat into electricity. In such systems, heated water vapor rotates a turbine and sets in motion an electric generator, the magnetic field of which creates an alternating current.
Physicists note that, on average, steam turbinesreliably convert about 35% of heat into electricity. In addition, the moving parts of the system are sensitive to temperature, so high temperature heat sources cannot work with such turbines.
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