Solar energy introduction

The sun has provided energy directly to humans for a long time, but the use of mechanical devices to convert solar energy into other forms of energy is still a modern matter.

Solar energy generally refers to the radiant energy of sunlight. The nuclear reaction from the "hydrogen" to the "氦" carried out inside the sun constantly releases huge energy and continuously radiates energy to the space, which is solar energy. This nuclear fusion reaction inside the sun can last for several billion to tens of billions of years.

The radiant power emitted by the sun into space is 3.8x10^23 kW, of which one billion is reaching the Earth's atmosphere. 30% of the solar energy reaching the Earth's atmosphere is reflected by the atmosphere, 23% is absorbed by the atmosphere, and the rest reaches the surface of the Earth. Its power is 800 billion kW, which means that the sun's energy per second is equivalent to burning 5 million. The heat released by tons of coal. The average energy received per minute per square meter of area outside the atmosphere is approximately 1367W.

Solar energy in a broad sense is a source of many energy on Earth, such as wind energy, biomass energy, water energy, and so on. Narrowly defined solar energy is limited to the direct conversion of solar thermal energy to photothermal, optoelectronic and photochemical.

Humans have a long history of using solar energy. As early as the Warring States Period more than 2,000 years ago, China knew that it would use steel four-sided mirrors to focus on the sun to ignite; use solar energy to dry agricultural and sideline products. In the modern era, the use of solar energy has become increasingly widespread, including the solar thermal utilization, the photovoltaic utilization of solar energy and the photochemical utilization of solar energy. The use of solar energy has two modes: photothermal conversion and photoelectric conversion.

Solar water heaters are devices that use the heat of sunlight to heat water. They are one of the most widely used methods of solar thermal utilization. The promotion and application of solar greenhouses, solar plastic greenhouses and other devices have prolonged the growth period of crops such as vegetables, and brought great changes to agricultural production and the lives of urban and rural residents. Through photothermal conversion, solar energy can be used for thermal storage and heat generation. Seawater desalination can also be carried out using solar energy.

Solar power is an emerging form of renewable energy use. The solar cell is used to convert the energy contained in sunlight into electrical energy through photoelectric conversion. At present, the use of solar cells is not very popular, and the use of solar power has the problems of high cost and low conversion efficiency, but solar cells play a major role in providing energy for artificial satellites.