Modern solar energy is based on photoelectric conversion using semiconductors. For the conversion of solar radiation, only parts of the solar radiation spectrum are used in this way. The main part of such radiation (Planck spectrum) can not be used, since it is not absorbed and not transformed by available methods. However, if using nanofluids, for example, based on graphene flakes or nanotubes, it is possible, due to the strong absorption of the thermal spectrum of solar radiation, to effectively heat the working fluids to the formation temperature of steam. The results of experimental studies of such heating with the use of a solar radiation imitator are demonstrated, calculations of the absorption of radiation and heating of working fluids with very high efficiency are made. Conclusions are made about the possibility of creating new solar thermal power plants based on direct conversion of solar radiation from the whole Planck spectrum to steam. The possibility of using nanofluids as a coolant in solar concentrators was considered. In such solar thermal conversion system, special absorbers are used to absorb solar radiation, with a large absorption coefficient, which heats up giving off heat to the heat carrier, the absorber is used as in the coolant. In our work, we studied various nanofluids, for example, graphene nanocolloids and nanodiamond colloids. When using a nanofluid (carbon nanocolloids), the basic idea is to avoid absorbing solar radiation on the channel walls, since the nanofluids themselves have a high absorbing capacity, in this case there will be bulk absorption of nanoparticles. To achieve this goal, we first of all measured the absorption coefficients, the transmittance of nanofluids, but, in addition, other important measurements and calculations were made: 1). the absorption and transmission coefficients of nanofluids were measured and compared with distilled water, 2). according to the Bouguer-Lambert-Beer law, the intensity of the transmitted solar radiation was calculated through a layer of nanofluid, 3). the effect of nanoparticles on liquid heating has been studied, 4). the viscosity of the nanofluid is calculated.
This work was supported by the Russian Science Foundation (project No. 17-19-01757).
Advanced materials for energy generation and transmission , Photovoltaic and solar energy systems
