Solar energy is produced by the hydrogen 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. Coal, oil, natural gas and other fossil fuels are also primary energy formed by the evolution of ancient buried animals and plants through a long geological age. The energy contained in the earth itself usually refers to the energy related to the heat 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 the atomic nucleus changes, it can release a lot of energy, which is called atomic nuclear energy, referred to as nuclear energy, commonly known as atomic energy. It comes from the nuclear fission energy resources during fission reactions such as uranium and plutonium stored in the earth's crust, and the nuclear fusion energy resources during fusion reactions such as deuterium, tritium and lithium stored in the ocean. These substances release energy when nuclear reactions occur. At present, the biggest use of nuclear energy is power generation. In addition, it can also be used as other types of power source, heat source, etc.

Solar energy is the energy produced by the continuous nuclear fusion reaction inside the sun. The average radiation intensity on earth is 1369w /. The circumference of the earth's equator is 40076 kilometers, so it can be calculated that the energy obtained by the earth can reach 173000 tw. The standard peak intensity at sea level is 1kW / m2, and the 24h annual average radiation intensity at a certain point on the earth's surface is 0.20kw/m2, equivalent to 102000tw of energy.

Although the energy radiated by the sun into the earth's atmosphere is only one of 2.2 billion of its total radiation energy, it has reached 173000tw, that is, the energy irradiated by the sun on the earth per second is equivalent to 5 million tons of coal and 1.465 tons of energy irradiated on the earth per second × 10 ^ 14 joules. Wind energy, water energy, ocean temperature difference energy, wave energy and biomass energy on the earth all come from the sun; Even the fossil fuels on the earth (such as coal, oil, natural gas, etc.) are basically solar energy stored since ancient times, so the scope of solar energy in the broad sense is very large, while solar energy in the narrow sense is limited to the direct conversion of solar radiant energy to photothermal, photoelectric and photochemical.