There are many types of energy family members. Generally, we add all kinds of sources that can be used by humans to obtain useful energy into the energy family, and through continuous development and research by humans, more new energy sources have begun to meet human needs. According to different division methods, energy can also be divided into different types.
1. Classification by energy source
Energy can be divided into the following 3 categories according to its source:
① The energy from celestial bodies outside the earth mainly refers to solar energy. In addition to direct radiation, this type of energy provides the basis for the production of wind, hydro, biomass, and fossil energy.
Most of the energy needed by humans comes directly or indirectly from the sun. In addition to the direct use of its light and heat, solar energy is also the main source of many kinds of energy on the earth. It is various plants that convert solar energy into chemical energy through photosynthesis and store it in the plant. Fossil fuels such as coal, oil, and natural gas are also formed by ancient plants and animals buried in the ground after a long geological age. They are essentially solar energy fixed by ancient creatures. In addition, water energy, wind energy, wave energy, ocean energy, etc. are also converted from solar energy. In terms of quantity, solar energy is huge. Theoretical calculations show that the energy radiated to the earth by the sun per second is equivalent to the heat released when more than 5 million tons of coal is burned; there are equivalent to 170 trillion tons of coal in a year, and the energy consumed by the world in a year is still Less than one ten thousandth of it. However, only one-thousandth of the solar energy that reaches the earth's surface is absorbed by plants and converted into chemical energy for storage. Most of the rest is converted into heat and radiated into space.
② 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.
One of them is the geothermal energy contained in the earth. Common underground steam, hot springs, and volcanic eruptions are all geothermal energy. The earth is a large thermal reservoir, from the ground down, as the depth increases, the temperature also increases. The earth can be divided into three layers: crust, mantle and core. The crust is a layer on the surface of the earth, generally ranging in thickness from several kilometers to 70 kilometers. Below the crust is the mantle, most of which is molten magma with a thickness of 2,900 kilometers. A volcanic eruption is usually the ejection of this part of magma. The inner part of the earth is the core of the earth, and the temperature of the core is 2000 degrees. Hot springs from the ground and magma from volcanic eruptions are manifestations of geothermal heat. The earth's geothermal resource reserves are also very large. According to current drilling technology, it can be drilled to a depth of 10 kilometers underground. It is estimated that the total geothermal energy resources are equivalent to more than 4 million times the world's annual energy consumption.
The other is the nuclear energy contained in nuclear fuels such as uranium, thorium, and lithium that exist on the earth. Nuclear reactions mainly include fission and fusion reactions. At present, more than 440 nuclear power plants in operation around the world use the heat released by uranium nuclear fission. Nuclear power plants that use atmosphere, tritium, lithium and other light nuclear fusion to release energy are under study. The proven reserves of uranium in the world are about 4.9 million tons and the reserves of thorium are about 2.75 million tons. These fission fuels are enough for humans to use to welcome the arrival of fusion energy. Fusion fuels are mainly deuterium and lithium. The content of deuterium in seawater is 0.03 g/L. It is estimated that the amount of seawater on the earth is about 13.8 billion cubic meters3, so the world's reserves of deuterium are about 40 trillion tons; lithium on the earth Although the reserves are much smaller than atmosphere, there are more than 200 billion tons. Using it to make tritium is enough for human beings to transition to the age of deuterium and deuterium fusion. The energy released by these fusion fuels is tens of millions of times greater than the total amount of energy currently available in the world. According to the current level of world energy consumption, the deuterium and tritium available for nuclear fusion on the earth can be used by humans for hundreds of billions of years. Therefore, as long as nuclear fusion technology is solved, mankind will fundamentally solve the energy problem. Realizing controllable nuclear fusion to obtain inexhaustible and inexhaustible fusion energy is exactly what nuclear scientists are diligently seeking.
③The energy produced by the interaction between the earth and other celestial bodies. The regular movement of the earth, moon, and sun causes periodic changes in their relative positions. The gravitational force generated between them causes the sea to rise and fall to form tidal energy. Compared with other energy sources, the amount of tidal energy is very small. The world's tidal energy is converted into coal at about 3 billion tons per year, but the only part of the shallow sea area that is actually available is about 60 million tons of coal per year.
The above three types of energy are all existing, unprocessed or converted energy sources in nature.
2. Classification according to the basic form of energy utilization
According to the basic forms of energy utilization, there are primary energy and secondary energy. Primary energy refers to energy resources that exist in nature and have not been processed or converted. Three energy sources including water, oil and natural gas are the core of primary energy, and they become the foundation of global energy; in addition, Renewable energy sources such as solar energy, wind energy, geothermal energy, ocean energy, biological energy, and nuclear energy are also included in the scope of primary energy; secondary energy refers to the direct or indirect conversion of primary energy into other types and forms of energy resources. For example: electricity, gas, gasoline, diesel, coke, clean coal, laser, and biogas are all secondary energy sources. Residual energy and waste heat discharged during the production process, such as high-temperature flue gas, combustible waste gas, and waste steam are also secondary energy sources. No matter how many times the primary energy is converted, the other energy is called the secondary energy. For example, the thermal energy, mechanical energy, and electrical energy in the process of hydropower and thermal power generation are all secondary energy sources.
Primary energy can be divided into renewable energy and non-renewable energy according to whether it can be supplemented from nature. Solar radiant energy, water energy, biomass energy, wind energy, tidal energy, ocean thermal energy and wave energy are all energy sources that can be continuously regenerated and supplemented or can be regenerated in a short period of time, so they are called renewable energy. renewable energy. Fossil fuels such as coal, oil, natural gas, and nuclear fuels such as uranium and needles are all left over hundreds of millions of years ago. energy.
Geothermal energy is basically a non-renewable energy source, but judging from the huge reserves inside the earth, it has the nature of regeneration. The new development of nuclear energy will give the nuclear fuel cycle a proliferative nature. The energy of nuclear fusion can be 5-10 times higher than that of nuclear fission. The most suitable fuel for nuclear fusion, heavy hydrogen (deuterium), is present in sea water in large amounts, which can be described as "inexhaustible and inexhaustible." Nuclear energy is one of the pillars of the future energy system.
3. Classification according to the nature of energy
According to the nature of energy, there are fuel-based energy (coal, oil, natural gas, peat, wood) and non-fuel-based energy (hydropower, wind energy, geothermal energy, ocean energy). The use of energy other than physical strength by humans began with fire. The earliest fuel was wood, and various fossil fuels, such as coal, oil, natural gas, and peat, were used in the future.
Fuel energy is used as fuel, mainly in the form of heat energy. Fuel is a substance that can generate heat and light energy when burned. Fuel energy includes fossil fuels, such as coal, oil, gas, etc.; biofuels, such as algae, wood, biogas, various organic wastes, etc.; and nuclear fuels such as uranium and thorium. Fuel energy can also be divided into three types: solid (coal, wood, uranium, etc.), liquid (oil, alcohol) and gas fuel (natural gas, hydrogen). Except for nuclear fuel, which contains atomic energy, all other fuels contain chemical energy, and some also contain mechanical energy. Through combustion, the energy in the fuel is converted into heat energy for direct use, or the heat energy is converted into mechanical energy and electrical energy for use. Fuel energy is the basic energy for mankind at present and for a long period of time in the future.
Non-fuel energy is not used as fuel. Non-fuel energy is an energy source that can directly generate energy for human use. Such as water energy, wind energy, tidal energy, ocean energy, laser energy, etc., most of which contain mechanical energy, and some also contain heat, light, and electrical energy.
4. Classification according to whether energy can cause pollution
According to whether energy consumption causes environmental pollution, it can be divided into polluting energy and clean energy. Polluting energy includes coal and petroleum; clean energy includes water, electricity, solar, wind, and nuclear energy.
5. Classification according to energy use
According to energy use, it can be divided into conventional energy and new energy. The utilization technology is mature and the commonly used energy is called conventional energy, including renewable water resources and non-renewable coal, oil, natural gas and other resources in the primary energy. Conventional energy, also known as traditional energy, is an energy with relatively mature technology that has been widely used by people under the current scientific and technological level. For example, coal, petroleum, natural gas, water energy, etc. are conventional energy sources, and the energy directly or indirectly converted from these conventional energy sources, such as gas, coke, gasoline, alcohol, electricity, steam, etc., are also classified as conventional energy sources. This is in contrast to new energy.
The energy that is newly used or is being developed is called new energy. New energy sources are relative to conventional energy sources, including solar energy, wind energy, geothermal energy, ocean energy, biological energy, hydrogen energy, and nuclear fuel for nuclear power generation. Because the energy density of new energy is low, or the grade is low, or it is intermittent, or the economic efficiency of conversion and utilization according to existing technical conditions is still poor, and it is still in the research and development stage, it can only be developed and used according to local conditions; but Most of the new energy is renewable energy. These energy resources are abundant and widely distributed, and are one of the main energy sources in the future.
Conventional energy and new energy are relative terms, and "conventional" means commonly used. "New" has two meanings: one is that it has only been used since the middle of the 20th century; the other is that it has been used before, and now there are new ways to use it. The essential difference between them is the difference in the use of time. Of course, with the passage of time and the advancement of science and technology, new energy sources will gradually become conventional energy sources. For example, oil was a great new energy source in the second half of the 19th century, and it is now also a conventional energy source. Another example is that nuclear energy has been regarded as a conventional energy source in developed countries, while it is considered a new energy source in developing countries.
6. Classification according to the morphological characteristics of energy
The World Energy Commission recommends classification according to the morphological characteristics of energy. Energy can be divided into: 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 types are collectively referred to as fossil fuels or fossil energy. The above-mentioned energy that has been recognized by humans can be converted into a certain form of energy required by humans under certain conditions. For example, firewood and coal, heating them to a certain temperature, they can combine with the oxygen in the air to release a large amount of heat energy. We can use heat for heating, cooking or cooling, or use heat to generate steam, and use steam to drive a steam turbine to turn heat energy into mechanical energy; or use a steam turbine to drive a generator to turn mechanical energy into electrical energy; It can be converted into mechanical energy, light energy or heat energy in factories, enterprises, institutions, agriculture, animal husbandry and forestry areas and households.
7. Commodity energy and non-commodity energy
All products that enter the energy market and are sold as commodities, such as coal, oil, natural gas, and electricity, are all commodity energy sources. International statistics are limited to commercial energy. Non-commercial energy mainly refers to firewood and crop residues (straw, etc.). In 1975, the world's non-commercial energy was about 0.6 terawatt-year, equivalent to 600 million tons of standard coal. It is estimated that China’s non-commercial energy in 1979 was approximately 290 million tons of standard coal.
With the increasing demand for energy in the economic development of countries around the world, many developed countries are now paying more attention to the development and research of renewable energy, environmentally friendly energy and new energy; at the same time, we also believe that with the continuous advancement of human science and technology, experts We will continue to develop and research more new energy sources to replace existing energy sources to meet the high demand for energy for global economic development and human survival, and we can predict that there are many new energy sources on the earth that have not yet been discovered by humans waiting for us to explore And research.