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- How the energy is generated
According to the way of energy generation, it can be divided into primary energy and secondary energy.
(1) Primary energy
Primary energy refers to the energy that exists in natural form in nature, which directly comes from nature without being processed and converted by people, so it is also called natural resource. Coal, oil, natural gas, hydropower, solar energy, wind energy, biomass energy, ocean energy, geothermal energy, etc. are all primary energy sources. Usually what we call energy refers to primary energy.
Primary energy is called energy resources when it is in a state of natural occurrence before being developed by humans. The energy production and consumption of countries in the world generally refer to primary energy. In order to facilitate comparison and calculation, it is customary to convert various primary energy sources into “standard coal” or “oil equivalent” as a unified unit of measurement for various energy sources.
(2) Secondary energy
Secondary energy means that people convert it into an energy form that meets people’s requirements on the basis of primary energy. Electricity, gasoline, diesel, coke, coal gas, steam, hydrogen energy, etc. are all secondary energy sources.
The residual pressure and heat generated in the production and life processes (such as high-temperature flue gas discharged from the boiler flue, combustible exhaust gas, waste steam, waste hot water discharged from the reaction device, and pressurized fluid discharged from the closed reactor, etc.) Belongs to secondary energy. In today’s energy shortage, human beings also make full use of the “waste” secondary energy in these industrial production processes, such as using waste heat from cement kilns to generate electricity, and using steel waste heat from steel plants to generate electricity.
Primary energy only serves humans in its original form in a few cases, and more often needs to be processed for different purposes and converted into easy-to-use secondary energy to meet needs or improve energy efficiency. With the development of science and technology and the modernization of society, the proportion of secondary energy in the entire energy consumption system will increase.
- The nature of energy
According to the nature of energy, energy can be divided into process energy and energetic energy.
(1) Process energy
Process energy refers to energy that cannot be stored directly. It is a material movement process with relatively concentrated energy, or energy process, which can generate energy during material flow, such as flowing water, ocean currents, tides, wind, electricity, ocean energy, etc. Among them, electric energy is the most widely used process energy
(2) Energetic energy
Energetic energy refers to substances containing energy that can be stored directly, such as fossil fuels, plant fuels, nuclear fuels, etc. Among them, fossil fuels such as diesel and gasoline are the most widely used energy sources. Because process energy cannot be directly stored in large quantities, modern transportation vehicles with strong mobility such as automobiles, ships, and airplanes cannot directly use the electrical energy output from power plants. They can only use energy such as diesel and gasoline. Energy energy. It can be seen that process energy and energetic energy cannot replace each other.
With the ever-increasing consumption of fossil fuels, the reserves of energetic energy sources are declining and will eventually be exhausted. There is an urgent need to find a new energy-containing energy that does not rely on fossil fuels and has abundant reserves. Hydrogen energy is exactly a new energy-containing energy that people are looking forward to when the conventional energy is in crisis.
- The status of energy
According to the status of various energy sources in contemporary human social and economic life, people often divide energy sources into two categories: conventional energy and new energy.
(1) Conventional energy
Technically mature, energy that has been mass-produced and widely used by mankind is called conventional energy, also known as conventional energy (Conventional Energy). Conventional energy takes a long time to use, such as coal, oil, natural gas, hydropower, and nuclear fission. Can wait. At present, the world’s energy consumption is almost entirely supplied by these five energy sources. For a long time to come, they will still play the leading role on the world energy stage.
Coal, oil, natural gas, etc. are fossil energy sources, also known as fossil fuels or mineral fuels. They are a mixture of hydrocarbons or hydrocarbon derivatives, including natural resources such as coal, oil, and natural gas, which are non-renewable resources.
(2) New energy
The energy that has not yet been used on a large scale by humans and needs to be further studied, tested and developed is called new energy. For example, solar energy, wind energy, geothermal energy, ocean energy and nuclear fusion energy. The so-called new energy is relatively speaking. The current conventional energy was also a new energy in the past, and today’s new energy will also become a conventional energy in the future.
Due to the low energy density, low grade, and intermittent energy of new energy, the economic efficiency of new energy conversion and utilization according to the existing technical conditions is still poor, and it is still in the research and development stage, and can only be developed and utilized according to local conditions; Most of the energy is renewable energy, which is rich in resources and widely distributed, and is one of the main energy sources in the future.
- Is the energy renewable?
Primary energy is divided into renewable energy and non-renewable energy according to whether it can be regenerated and recycled.
(1) Renewable energy
Renewable energy is energy that will not decrease with its own conversion or human use, and it has natural recovery capabilities. Such as solar energy, wind energy, water energy, biomass energy, ocean energy and geothermal energy, etc., are all renewable energy sources
(2) Non-renewable energy
Non-renewable energy refers to those energy sources that are gradually reduced with human use, such as fossil fuels and nuclear fuels. Fossil fuels and nuclear fuels have been formed for hundreds of millions of years and cannot be regenerated in a short period of time. They are becoming more and more with human use. few.
- Source of energy
According to the source classification, energy can be divided into three types: the first type of energy, the second type of energy, and the third type of energy.
(1) The first type of energy
The first type of energy is energy from celestial bodies outside the earth, mainly solar energy and coal, oil, natural gas, and biomass energy as a form of solar energy solidification, and wind energy, water energy, and seawater temperature difference energy as a form of solar energy conversion.
Most of the energy needed by humans comes directly or indirectly from the sun. In addition to direct radiation, solar energy can provide a basis for the production of wind energy, hydropower, biomass and fossil energy. Plants convert solar energy into chemical energy through photosynthesis and store it in the plant. This part of the energy provides energy for the survival of animals and humans.
Fossil fuels such as coal, oil, and natural gas were formed by ancient animals and plants buried in the ground over a long geological age. They are essentially solar energy fixed by ancient organisms.
(2) The second type of energy
The second type of energy is the energy contained in the earth itself. The energy contained in the earth itself usually refers to the energy or nuclear energy related to the thermal energy inside the earth, such as geothermal energy such as underground hot water, underground steam, magma, and nuclear energy contained in nuclear fuels such as uranium and needles.
Magma ejected from hot springs and volcanic eruptions is a manifestation of geothermal energy. The earth’s core is dominated by metallic iron and nickel. It is an extremely hot world with a temperature of over 7000°C. Therefore, the earth’s geothermal resources are stored in large quantities.
(3) The third type of energy
The third type of energy is the energy produced by the interaction between the earth and other celestial bodies, that is, the energy related to the interconnection of the earth, the moon, and the sun, such as tidal energy.
Tidal energy is the energy obtained from the day and night fluctuations of sea level, and is related to the gravitation of celestial bodies. The attraction and heat of the earth-moon-sun system are the sources of tidal energy.
As early as the 11th century, Britain, France and Spain had waterwheels that used tidal energy. At that time, tidal waterwheels were used to absorb a small part of the total potential energy to produce 30-100kw of mechanical energy. China’s sea areas are quite rich in tidal resources, and there are various types of lakes, making it one of the sea areas with the most abundant types of ocean tides in the world.
The use of tidal energy to generate electricity can be divided into three forms: single-storage one-way, double-storage one-way, and single-storage two-way. During the high tide or low tide, the lake contains huge energy in and out of the reservoir, thereby driving the hydroelectric generator to generate electricity.
With the increasing demand for energy from economic development, many developed countries attach great importance to the development and research of renewable energy, environmentally friendly energy and new energy sources.
Nuclear fuel (Nuclear Fuel) is a material that produces nuclear energy through nuclear fission or nuclear fusion in a nuclear reactor. Nuclear materials cannot be burned, nor do they produce energy through combustion, but people usually refer to nuclear materials as nuclear fuel or nuclear fuel rods.
In order to meet the energy needs of the sustainable development of human society and prevent the serious pollution and ecological damage caused by the large-scale use of fossil energy, it is necessary to follow the energy path of sustainable development, that is, the path of clean energy.
Clean energy can be divided into two categories: narrow and broad. In a narrow sense, clean energy only refers to renewable energy, which can be restored and supplemented after consumption, and produces no or very little pollutants. Therefore, renewable energy is considered to be the foundation of the future energy structure.
In a broad sense, clean energy refers to energy that has as little or no pollution as possible to the ecological environment in the process of energy production, productization and consumption, including low-pollution natural gas, clean coal and clean oil and other fossil resources and renewable resources. And nuclear power.
In the future when the science and technology of human society reach a fairly high level and have corresponding economic support, clean energy in a narrow sense is the most ideal energy. However, in recent decades or even half a century, clean energy in a broad sense is more realistic for human society, because the large-scale utilization of renewable energy still requires major technological breakthroughs and substantial reductions in cost prices.