Today, with the rapid development of the new century, energy has become an important factor restricting the development of countries and a vital part of people’s lives. Among many energy sources, the most directly used is electric energy. People have invented a variety of methods to convert other energy into electric energy. At present, thermal power generation is still the most widely used, while emerging energy power generation technologies include solar power generation, hydropower generation, wind power generation, nuclear power generation, garbage incineration power generation, and so on.
1.1: Overview of new energy technology
The United Nations Conference on New and Renewable Energy, held by the United Nations in 1980, defined new energy as: based on new technologies and new materials, to modernize the development and utilization of traditional renewable energy, to replace fossil energy with inexhaustible renewable energy that has limited resources and pollutes the environment, and to focus on the development of solar energy, wind energy, biomass energy, tidal energy, geothermal energy, hydrogen energy and nuclear energy.
Generally speaking, conventional energy refers to the energy that is relatively mature in technology and has been used on a large scale, while new energy usually refers to the energy that has not been used on a large scale and is being actively researched and developed. Therefore, coal, oil, natural gas and large and medium-sized hydropower are regarded as conventional energy, while solar energy, wind energy, modern biomass energy, geothermal energy, marine energy, nuclear energy and hydrogen energy are regarded as new energy. With the progress of technology and the establishment of the concept of sustainable development, the industrial and domestic organic waste, which has been regarded as garbage in the past, has been re recognized, and has been deeply researched, developed and utilized as a material for energy resource utilization. Therefore, the resource utilization of waste can also be regarded as a form of new energy technology.
It is estimated that the annual solar radiation to the earth is 1.78 billion kilowatts, of which 50~100 billion kilowatt hours can be developed and utilized. However, due to its scattered distribution, little can be used at present. Geothermal energy resources refer to the total heat content of rocks and water bodies within a depth of 5000 meters underground. Among them, 1.4 million tons of standard coal are high temperature geothermal energy resources with a depth of 3 kilometers and a temperature above 150 ℃ in the global land. At present, some countries have started commercial development and utilization. The potential of wind energy in the world is about 350 billion kilowatts. Because of the intermittent dispersion of wind power, it is difficult to use it economically. If there are significant improvements in energy transmission and storage technology in the future, the use of wind power will increase. Ocean energy includes tidal energy, wave energy, seawater temperature difference energy, etc., and the theoretical reserves are very considerable. Limited to the technical level, it is still in the stage of small-scale research. At present, because the utilization technology of new energy is not yet mature, it only accounts for a small part of the total energy required by the world, and has a great future in the future.
2.1: Solar power generation technology
2.1.1 Overview of solar power generation technology
The solar interior is undergoing a violent nuclear reaction from hydrogen to helium, and constantly radiates huge energy into space, which can be said to be “inexhaustible” energy. The actual available amount of solar radiation energy on the ground is low as time, geographic latitude and climate change, but the available resources are still far greater than the total energy consumption of human beings and the planned energy utilization after 2100.
At present, the solar power generation technology in the United States, Australia, Germany and other countries is relatively mature, and Spain has put two 10MW solar power stations into use in recent years. China’s solar power generation technology started late, and only started some basic research until the 1970s. There is a big gap between China and developed countries. China’s solar workers have a long way to go.
The main disadvantages of solar energy are:
(1) It cannot generate electricity continuously, and is greatly affected by weather conditions such as season, day and night, as well as cloudy and sunny weather;
(2) It is difficult to accurately predict the power generation of the system;
(3) At present, the cost of photovoltaic system is relatively high, with the system cost of 40000~60000 yuan/kW
2.1.2: Principle of solar power generation
Solar power generation mainly includes two basic modes: solar photovoltaic power generation and solar thermal power generation. The utilization mode of converting solar energy directly into point energy without thermal process becomes solar photovoltaic power generation. At present, photovoltaic cells are actually used. Solar thermal power generation is a device that converts absorbed solar radiation heat energy into point energy. There are many types of solar thermal power generation, mainly including tower system, trough system, disk system, solar pond and solar tower thermal airflow power generation. The first three are concentrated solar thermal power generation systems, and the last two are non concentrated solar thermal power generation systems. Some developed countries have taken solar power generation technology as the national research and development focus, and manufactured dozens of solar thermal power generation demonstration power stations of various types, which has reached the practical application level of grid connected power generation.
2.2 Wind power generation
2.2.1 Overview of wind power generation technology
Wind energy is a kind of green energy. With the dual pressure of energy crisis and environmental protection, the development of wind power generation technology and the continuous reduction of equipment costs, wind energy has become a renewable energy with great economic utilization and industrial development value. According to the latest data provided by the European Wind Energy Summit, the global new capacity of wind power generation in 2005 was 11.8GW, an increase of 43.4% over 2004. At present, the total installed capacity of wind power generation in the world has reached 59.32GW, an increase of 25% over 2004. At present, Europe still holds the leading position in wind power generation, accounting for 69% of the total installed capacity in the world. From a worldwide perspective, it is estimated that in 2020, the installed capacity of wind power will reach 1.231 billion kW, the annual installed capacity will reach 150 million kW, and the annual power generation will be equivalent to 12% of the world demand at that time.
China’s wind power generation started in the late 1950s and then stagnated. In the mid-1970s, it received renewed attention under the influence of the world energy crisis. By 1991, it had been rapidly developed and promoted. By 2007, China had added 3144 wind turbines outside Taiwan Province, with a cumulative installed capacity of 5890MW.
Therefore, in a country building a resource conserving society, wind power generation is no longer an insignificant supplementary energy, but one of the emerging energy industries with the most commercial development prospects. Advantages of wind power generation:
- Clean, good environmental benefits;
- Renewable and never exhausted;
- Short capital construction period;
- Flexible installation scale.
Disadvantages:
- Noise and visual pollution;
- Occupying a large area of land;
- Unstable and uncontrollable;
- The cost is still high.
- It affects birds.
2.2.2 Principles of wind power generation
Wind power generation uses the wind to drive the windmill blades to rotate, and then increases the speed of rotation through the booster engine to promote the generator to generate electricity. According to the current windmill technology, a light wind speed of about three meters per second can start to generate electricity.
2.3 Nuclear power generation technology
2.3.1 Overview of nuclear power generation technology
In World War II, the explosion of the atomic bomb made people realize the power of nuclear energy. In June 1954, with the completion of the first nuclear power plant in the world in the Soviet Union, mankind’s peaceful use of nuclear energy also began.
Among the 30 countries with nuclear power generation capacity in the world, nuclear power generation capacity is very different. The percentage of electricity generated by nuclear reactors ranges from 78 per cent in France to 2 per cent in China. As of 2008, there are 439 nuclear reactors in the world, and another 35 are under construction. Among them, there are 104 in the United States, 59 in France, 55 in Japan, 31 in Russia and another 7 under construction. Nuclear power development is mainly in Asia, where 20 of the 35 reactors under construction are in Asia, and 28 of the 39 reactors recently connected to the grid for power generation are also in Asia.
For our country, nuclear energy plays an important role in the future energy structure. China’s air pollution is serious, greenhouse gas emissions are quite large, and nuclear power generation does not actually produce any greenhouse gases. More importantly, China is seriously short of per capita resources. Both oil and coal are important chemical raw materials. It is very important to develop and maintain certain reserves. From the perspective of sustainable development, the development of nuclear power is very beneficial to China’s energy structure. Nuclear power also has its drawbacks:
(1) Low resource utilization
(2) The nuclear waste generated after reaction has become a potential factor endangering the biosphere, and its final treatment technology has not been completely solved
(3) The safety problems of reactor still need to be monitored and improved continuously
(4) Constraints of nuclear non-proliferation requirements, i.e. plutonium-239 generated in nuclear power plant reactors is controlled
(5) The investment cost of nuclear power construction is still higher than that of conventional energy power generation, and the investment risk is high
2.3.2 Principles of nuclear power generation
The energy of nuclear power generation comes from the fission energy released by the fission reaction of the fissile material (nuclear fuel) in the nuclear reactor. Fission reaction refers to the process in which uranium 235, plutonium-239, uranium-233 and other major elements are split into two fragments under the action of neutrons, releasing neutrons and a large amount of energy at the same time. In the reaction, the nucleus of the fissionable material absorbs one neutron and then splits and releases two or three neutrons. If these neutrons are consumed, at least one neutron can cause the fission of another atom, which is carried out in a self-sustaining manner, then this reaction is called chain fission reaction, and the realization of chain fission reaction is the premise of nuclear power generation.
