The basic structure of the sun is a sphere made of hot gas, mainly composed of hydrogen and helium, of which hydrogen accounts for 80% and helium accounts for 19%. Solar energy is the energy produced by the continuous nuclear fusion reaction process inside the sun. The average solar radiation intensity in the earth’s orbit is 1367kW/m², and the circumference of the earth’s equator is 40 000 km. It can be calculated that the energy obtained by the earth can reach 173 000 TW. The standard peak intensity at sea level is 1KW/m², and the average annual radiation intensity at a certain point on the earth’s surface for 24 hours is 0.20KW/m², which is equivalent to 102,000 TW of energy. Humans rely on this energy for survival, including all other forms of energy. Renewable energy (except geothermal energy resources). Although the total amount of solar energy resources is equivalent to more than 10,000 times the energy used by human beings, the energy density of solar energy is low, and it varies from place to place and changes with time. This is the main problem facing the development and utilization of solar energy. These characteristics of solar energy will limit its role in the entire integrated energy system.
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 Stored solar energy, so the broad sense of solar energy includes a very large range, and the narrow sense of solar energy is limited to the direct conversion of solar radiant energy, photo-thermal, photoelectric, and photochemical.
Solar energy is both a primary energy source and a renewable energy source. It is rich in resources, can be used free of charge, does not require transportation, and does not pollute the environment. The total amount of solar energy is very large. The annual solar energy received by the land surface is very scattered, and the energy flow density is low. The solar energy reaching the ground is only about 1000w per square meter. At the same time, the solar energy on the ground is also affected by seasons, day and night, climate, etc. It is cloudy and sunny at times, strong at times and weak at times, which is unstable and restricts the effective use of solar energy.
Mankind has a long history of using solar energy. As early as the Warring States Period, China used steel four-sided mirrors to focus sunlight for ignition and use solar energy to dry agricultural and sideline products during the Warring States Period. In modern times, the use of solar energy has become increasingly widespread, including the use of solar heat, photoelectric use of solar energy, and photochemical use of solar energy. As a new energy source, solar energy has the following three advantages compared with conventional energy sources:
(1) It is the most abundant energy available to mankind. According to estimates, in the past 1.1 billion years, the sun has consumed 2% of its own energy, which can be said to be inexhaustible and inexhaustible.
(2) Solar energy is available everywhere on the earth, and it can be developed and utilized on the spot. There is no transportation problem. It is especially valuable for rural areas, islands and remote areas with underdeveloped transportation.
(3) Solar energy is a kind of clean energy. When it is developed and utilized, it will not produce waste residue, waste water, exhaust gas, noise, and will not affect the ecological balance.