1, according to the source, it can be divided into three categories: the energy contained in the earth itself usually refers to the energy related to the thermal energy in the earth and the energy related to the nuclear reaction.
(1) energy from celestial bodies outside the earth (mainly solar energy). In addition to direct radiation, it also provides a basis for the generation of wind energy, water energy, biological energy and mineral energy. Most of the energy needed by human beings comes directly or indirectly from the sun. It is all kinds of plants that convert solar energy into chemical energy through photosynthesis and store it in plants. Fossil fuels such as coal, oil and natural gas are also formed by ancient plants and animals buried underground after a long geological age. They are essentially the fixed solar energy of ancient creatures. In addition, water energy, wind energy, wave energy and ocean current energy are also converted from solar energy.
② The energy contained in the earth itself. Such as nuclear energy and geothermal energy.
(3) the energy generated by the interaction between the earth and other celestial bodies. Such as tidal energy. The magma ejected from hot springs and volcanic eruptions is the expression of geothermal energy. The earth can be divided into three layers: crust, mantle and core. This is a large thermal storage. The earth's crust is a layer of the earth's surface, and its thickness generally ranges from several kilometers to 70 kilometers. Below the crust is the mantle, mostly molten magma, with a thickness of 2900 kilometers. Volcanic eruptions are usually caused by this part of magma. Inside the earth is the core, and the temperature of the core center is 2000 degrees. It can be seen that the geothermal resources on the earth are also great.
2. According to the basic forms of energy, there are primary energy and secondary energy. The former, natural gas energy, refers to the ready-made energy in nature, such as coal, oil, natural gas, hydropower and so on. The latter refers to energy products transformed from primary energy processing, such as electricity, gas, steam and various petroleum products. Primary energy is divided into renewable energy (hydropower, wind energy and biomass energy) and non-renewable energy (coal, oil, natural gas and oil shale). ). According to the production mode, it can be divided into primary energy (natural gas energy) and secondary energy (artificial energy). Primary energy refers to energy resources that exist in natural form and have not been processed or transformed. Primary energy includes renewable hydraulic resources and non-renewable coal, oil and natural gas resources, among which water, oil and natural gas are the core of primary energy and become the basis of global energy. In addition, renewable energy such as solar energy, wind energy, geothermal energy, ocean energy, bioenergy and nuclear energy are also included in the category of primary energy; Secondary energy refers to the direct or indirect transformation of primary energy into other types and forms of energy resources, such as electricity, natural gas, gasoline, diesel, coke, clean coal, laser, biogas and so on.
3. According to the nature of energy, there are fuel energy (coal, oil, natural gas, peat and wood) and non-fuel energy (hydropower, wind energy, geothermal energy and ocean energy). Humans have used fire to use energy other than their own physical strength from the beginning. The earliest fuel was wood, and later various fossil fuels were used, such as coal, oil, natural gas and peat. New energy sources such as solar energy, geothermal energy, wind energy and tidal energy are being studied and utilized. At present, the consumption of fossil fuels is large, but the reserves of these fuels on the earth are limited. In the future, uranium and thorium will provide most of the energy needed by the world. Once the technical problem of controlling nuclear fusion is solved, mankind will actually get endless energy.
4. According to whether energy consumption causes environmental pollution, it can be divided into polluting energy and clean energy. Pollution energy includes coal and oil, and clean energy includes hydropower, electricity, solar energy, wind energy and nuclear energy.
5. According to the types of energy use, it can be divided into conventional energy and new energy. Conventional energy includes renewable hydraulic resources and non-renewable coal, oil, natural gas and other resources in primary energy. Compared with conventional energy sources, new energy sources include solar energy, wind energy, geothermal energy, ocean energy, biomass energy and nuclear fuel for nuclear power generation. Because the energy density of new energy is low, or the grade is low, or intermittent, the economy of conversion and utilization according to the existing technical conditions is still poor, and it is still in the research and development stage, so it can only be developed and utilized according to local conditions; But most of the new energy sources are renewable. It is rich in resources and widely distributed, and will be one of the main energy sources in the future.
6. People usually classify energy sources according to their morphological characteristics or the level of transformation and application. The types of energy recommended by the World Energy Committee are: solid fuel, liquid fuel, gas fuel, hydropower, electric energy, solar energy, biomass energy, wind energy, nuclear energy, ocean energy and geothermal energy. Among them, the first three are collectively referred to as fossil fuels or fossil energy. The above energy has been recognized by human beings and can be converted into some form of energy that people need under certain conditions. Such as firewood and coal, when heated to a certain temperature, they can combine with oxygen in the air and release a lot of heat energy. We can use heat for heating, cooking or refrigeration, and we can also use heat to generate steam, which can drive a steam turbine to change thermal energy into mechanical energy. You can also use a steam turbine to drive a generator to turn mechanical energy into electrical energy; If electricity is sent to factories, enterprises, institutions, agricultural and pastoral areas and families, it can be converted into mechanical energy, light energy or heat energy.
7. Commodity energy and non-commodity energy, such as coal, oil, natural gas and electricity, which enter the energy market and are sold as commodities, are all commodity energy. International statistics are limited to commodity energy. Non-commodity energy mainly refers to firewood and crop residues (straw, etc.). From 65438 to 0975, the global non-commodity energy was about 0.6 terawatt-year, equivalent to 600 million tons of standard coal. It is estimated that the non-commodity energy in China 1979 is about 290 million tons of standard coal.
8. Renewable energy and non-renewable energy People further classify primary energy. Any energy that can be continuously replenished or regenerated in a short period of time is called renewable energy, and vice versa. Wind energy, water energy, ocean energy, tidal energy, solar energy and biomass energy are all renewable energy sources; Coal, oil and natural gas are non-renewable energy sources. Geothermal energy is basically non-renewable energy, but from the huge reserves on the earth, it is renewable. The new development of nuclear energy will make the nuclear fuel cycle diffuse. The energy of nuclear fusion is 5 ~ 10 times higher than that of nuclear fission, and the most suitable fuel for nuclear fusion, deuterium, is abundant in seawater, which can be described as "inexhaustible". Nuclear energy is one of the pillars of the future energy system.
With the increasing demand for energy in the economic development of countries around the world, many developed countries now pay more attention to the development and research of renewable energy, environmental protection energy and new energy; At the same time, we also believe that with the continuous progress of human science and technology, experts will continue to develop and study more new energy sources to replace existing energy sources, so as to meet the large demand for energy for global economic development and human survival, and we can foresee that there are still many new energy sources on the earth that have not been discovered by human beings waiting for us to explore and study. Conventional energy and new energy, which have been widely used by human beings and played an important role in human life and production, are called conventional energy, usually referring to coal, oil, natural gas and hydropower. The energy resources that have just been developed and utilized by human beings and need further research and development are called new energy sources. Compared with conventional energy, new energy has different contents in different historical periods and scientific and technological levels. In today's society, new energy usually refers to nuclear energy, solar energy, wind energy, geothermal energy, hydrogen energy and so on.