Scientists in the USA They have experimentally demonstrated the possibility of producing electricity using the temperature difference between Earth and space. The study, published in Applied Physics Letters , reported that physicists managed to generate 64 nanowatts of power per square meter of installation, a small but remarkable amount.
The standard version of solar cells is a photodiode, a semiconductor device that generates current when photons are irradiated from a source heated to a higher temperature. However, it is possible to carry out in a certain sense the inverse scheme, in which frame a photodiode with a higher temperature interacts through the radiation with a cold surface. In this case, it is said that the diode is in a state of negative illumination.
Physicists, several years ago, showed that under ideal conditions and absorption only in a narrow range, the efficiency of energy production tends to marginal efficiency in thermal engines, defined by Carnot’s theorem.
The radiation of the Earth
In general, energy can be generated in all situations where there is a flow of heat from a body warmer to a less hot one. The usual in this case is the conversion of the energy of solar radiation into electricity on the surface of a relatively cooler Earth. However, one can also use the radiation of the Earth itself, in which case the rest of the Universe will be the cold body, the average temperature at which it is determined by the photons of the CMB is approximately 2.7 Kelvin.
The use of the infrared luminescence of bodies on Earth allows potentially creating renewable energy sources that operate according to the same principles as solar panels but operate at night.
In a study led by Shanhui Fan of Stanford University, the production of electrical energy using a photodiode aimed at the night sky was experimentally demonstrated for the first time. “We experimentally demonstrate the generation of electrical energy directly from the coldness of the Universe,” the scientists write.
The authors used radiation at wavelengths of 8 to 13 microns, for which the atmosphere is transparent. As a result, they managed to generate an electric current with a power of approximately 64 nanowatts per square meter of installation. The energy conversion efficiency was 2.3 × 10% -5%. Such values are associated with the imperfect correspondence of the parameters of the diode used and the window of atmospheric transparency, as well as other parasitic effects.
Low, but theoretically useful
The researchers constructed a theoretical model that takes into account both the losses in the atmosphere and the non-ideality of the diode. As a result, they conclude that the theoretical limit of such facilities is approximately 4 watts per square meter, that is, approximately one million times more than what was shown in the current work.
Despite the fact that it is significantly less than the generation of modern solar cells, for which typical values are at the level of 100-200 watts per square meter, the use of negative lighting, in theory, should be sufficient for many devices work at night. Another use of this technology may be the use of heat dissipated by parts of heated machines.
Recently, researchers have taught the photo matrix to simultaneously generate energy from the recorded light and correct it. In addition, scientists have demonstrated the possibility of converting light into electricity in non-living natural systems, some types of soil and mineral crusts that form on the surface of stones in a dry and hot climate.