Solar energy is a kind of renewable energy. It refers to the thermal radiation energy of the sun (see the three ways of thermal energy transmission: radiation), which is mainly represented by the sun's rays. In modern times, it is generally used to generate electricity or provide energy for water heaters.

Since the birth of life on the earth, it has mainly lived by the thermal radiation energy provided by the sun. Since ancient times, humans have also learned to use the sun to dry objects and use it as a method of making food, such as salt and salted fish. With the decrease of fossil fuels, solar energy has become an important part of human energy use and has been continuously developed. There are two ways to use solar energy: photothermal conversion and photoelectric conversion. Solar power generation is an emerging renewable energy. In a broad sense, solar energy also includes wind energy, chemical energy and water energy on the earth.