Solar energy is the energy produced by the continuous nuclear fusion reaction process inside the sun. The average solar irradiance (radiation intensity) in the earth’s orbit is 1367kw/m². The circumference of the earth’s equator is 40000km, so it can be calculated that the energy obtained by the earth can reach 173000Tw. The standard peak intensity at sea level is 1kW/m², and the 24-hour average annual irradiance at a certain point on the earth’s surface is 0.20kW/m², which is equivalent to 102,000 TW of energy. Humans rely on this energy to survive. The sun is a huge, long-lasting, and endless source of energy. Although the energy radiated by the sun into the earth’s atmosphere is only one-2.2 billionth of its total radiant energy (approximately 3.865×10^26 W), it is already as high as 173,000W. The energy is equivalent to 5.9×10^6tce. The earth’s wind energy, water energy, ocean temperature difference energy, wave energy and biomass energy, and part of the tidal energy all come from the sun; even the fossil fuels on the earth (such as coal, oil, natural gas, etc.) are fundamentally ancient Solar energy stored since. Therefore, the broad sense of solar energy includes a very large range, while the narrow sense of solar energy is limited to the direct conversion of solar energy, photoelectricity and photochemistry.
Solar photovoltaic power generation is an important form of solar energy utilization. It is a power generation method that uses solar cells to convert light energy into electrical energy. With the continuous advancement of technology, photovoltaic power generation may be one of the most promising power generation technologies. The basic principle of solar cells is the photovoltaic effect of semiconductors, that is, the phenomenon of photovoltaic voltage generated under sunlight. In 1954, Bell Labs in the United States first invented a practically valuable crystalline silicon solar cell with a PN junction as the basic structure. Since then, solar cells have first been widely used in space technology, and are now gradually being applied on the ground.
Compared with fossil energy and nuclear power generation technologies, and also different from wind and biomass power generation technologies, photovoltaic power generation has a series of unique advantages, which can be summarized as follows.
(1) The principle of power generation is advanced, that is, direct conversion from photons to electrons, without intermediate processes (such as thermal energy-mechanical energy, mechanical energy-electromagnetic energy conversion, etc.) and mechanical movement, and the form of power generation is extremely simple. Therefore, theoretical analysis can get extremely high power generation efficiency, up to 80%. Due to the limitations of materials and processes, the efficiency of a single PN junction monocrystalline silicon cell studied in the laboratory is as high as 25%; and the efficiency of a compound semiconductor cell with multiple PN junctions has exceeded 40%. From the perspective of principle analysis and calculation and technological development potential, through 10 to 20 years of hard work, the realization of solar cell conversion efficiency in the range of 30% to 50% can be achieved.
(2) Solar energy resources are infinitely abundant, solar radiation is inexhaustible, renewable, and clean and environmentally friendly; the sun shines on the earth everywhere, without transportation, and the most important thing is that there is no hegemonic country to implement monopoly and control. may.
(3) The main raw material silicon used in photovoltaic power generation is rich in reserves, and its abundance ranks second in the earth’s crust after oxygen, reaching as much as 26%.
(4) Photovoltaic power generation has no combustion process, no greenhouse gas and other waste gas, no waste water, and it is environmentally friendly, and it is truly green power generation.
(5) The photovoltaic power generation system has no mechanical rotating parts, no mechanical wear, and no noise.
(6) Photovoltaic power generation system is easy to construct, install, disassemble and relocate, has a modular structure, and has a random scale, and it is easy to expand the installed capacity at any time.
(7) Decades of application and practice have proved that the performance of photovoltaic power generation system is stable and reliable, and the service life is more than 30 years.
(8) The photovoltaic power generation system can be unattended and has low maintenance costs.
Due to the high cost of solar photovoltaic power generation, there are still some difficulties in large-scale promotion and application in the country in the near future. But in the long run, with the advancement of technology and the gradual saturation of other forms of energy utilization, solar energy will become the mainstream form of energy utilization before and after 2050, with immeasurable development potential.