There are two ways of solar power generation, one is light heat electricity conversion, the other is light electricity direct conversion.
1.Optical thermal electrical conversion
The light heat electricity conversion mode uses the heat energy generated by solar radiation to generate electricity. Generally, the solar collector converts the absorbed heat energy into the steam of the working medium, and then drives the steam turbine to generate electricity. The former process is light heat conversion process; The latter process is the thermal electric conversion process, which is the same as ordinary thermal power generation. The disadvantage of solar thermal power generation is its low efficiency and high cost. It is estimated that its investment is at least 5 ~ 10 times higher than that of ordinary thermal power stations. A 1000MW solar thermal power station requires an investment of US $2-2.5 billion, with an average investment of US $2000-2500 for 1kW. Therefore, it can only be used in special occasions on a small scale, and large-scale utilization is not economical, and it can not compete with ordinary thermal power plants or nuclear power plants.
2.Optical electric direct conversion
Solar cell power generation is made according to the photoelectric properties of specific materials. Blackbody (such as the sun) radiates electromagnetic waves with different wavelengths (corresponding to different frequencies), such as infrared, ultraviolet, visible light, etc. When these rays irradiate on different conductors or semiconductors, photons interact with free electrons in conductors or semiconductors to produce current. The shorter the wavelength and the higher the frequency of rays, the higher the energy they have. For example, the energy of ultraviolet rays is much higher than that of infrared rays. However, not all wavelengths of ray energy can be converted into electrical energy. It is worth noting that the photovoltaic effect is independent of the intensity of the ray. Current can be generated only when the frequency reaches or exceeds the threshold that can produce photovoltaic effect. The maximum wavelength of the light that can make the semiconductor produce photovoltaic effect is related to the band gap width of the semiconductor. For example, the band gap width of crystalline silicon is about 1.155ev at room temperature. Therefore, the light with a wavelength less than 1100nm can make the crystalline silicon produce photovoltaic effect. Solar cell power generation is a renewable and environmentally friendly power generation method, which will not produce greenhouse gases such as carbon dioxide during the power generation process and will not pollute the environment. According to the production materials, it is divided into silicon-based semiconductor batteries, CdTe thin film batteries, CIGS thin film batteries, dye-sensitized thin film batteries, organic material batteries, etc. Silicon cells are divided into single crystal cells, polycrystalline cells and amorphous silicon thin film cells. The most important parameter for solar cells is the conversion efficiency. Among the silicon-based solar cells developed in the laboratory, the efficiency of monocrystalline silicon cells is 25.0%, the efficiency of polycrystalline silicon cells is 20.4%, the efficiency of CIGS thin film cells is 19.6%, the efficiency of CdTe thin film cells is 16.7%, and the efficiency of amorphous silicon (amorphous silicon) thin film cells is 10.1%
