Solar energy is generated by hydrogen and helium fusion of hydrogen atoms in the sun, which releases huge nuclear energy. It comes from the radiant energy of the sun. 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 contained 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 the nuclear fission energy resources of uranium and plutonium stored in the crust during the fission reaction, and the nuclear fusion energy resources of deuterium, tritium and lithium stored in the sea during the 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.