Application of solar energy: 1. Use solar cells to convert the energy contained in the sunlight into electrical energy through photoelectric conversion; 2. Use solar water heater to heat water with the heat of sunlight; 3. Use the heat of sunlight to heat water and use hot water to generate electricity; 4. Use solar energy for seawater desalination. Solar energy is a kind of renewable energy. It refers to the thermal radiation energy of the sun, which is mainly expressed as 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.

Solar energy is produced by the hydrogen and ammonia fusion of hydrogen atoms in the sun, which releases huge nuclear energy. It comes from the sun's radiant energy. Most of the energy needed by human beings comes directly or indirectly from the sun. Plants release oxygen and absorb carbon dioxide through photosynthesis, and convert solar energy into chemical energy for storage in plants. Fossil fuels such as coal, oil and natural gas are also primary energy formed by the evolution of ancient buried animals and plants over a long geological period. The energy stored in the earth itself usually refers to the energy related to the thermal energy inside the earth and the energy related to the nuclear reaction.

The energy related to nuclear reaction is nuclear energy. When the structure of atomic nucleus changes, it can release a large amount of energy, which is called atomic nuclear energy, or nuclear energy for short, commonly known as atomic energy. It comes from uranium stored in the earth's crust and nuclear fission energy resources during fission reaction, as well as gas, potassium and other nuclear fusion energy resources stored in the ocean during fusion reaction. These substances release energy when nuclear reactions occur. At present, the largest use of nuclear energy is power generation. In addition, it can also be used as other types of power source and heat source.