The basic source of solar heat is to collect solar radiation energy and convert it into heat energy through harmless interaction.
At present, the most widely used solar collectors are mainly flat plate collectors, vacuum tube collectors and focusing collectors. Generally speaking, according to the different temperatures and uses, solar photothermal utilization can be divided into low-temperature utilization (below 200℃), medium-temperature utilization (200~800℃) and high-temperature utilization (above 800℃). At present, low-temperature utilization mainly includes solar water heaters, solar dryers, solar distillers, solar houses, solar greenhouses, solar air conditioners and refrigeration systems. Medium temperature utilization mainly includes solar cookers and solar thermal power generation devices. High-temperature utilization mainly includes high-temperature solar furnaces. The following briefly introduces several main ways of solar energy thermal utilization.
① Direct utilization of solar light and heat. Solar collector mainly refers to solar water heater, which is the most common device for solar heat utilization. Its basic principle is to collect solar radiation energy and convert it into heat energy through interaction with matter for production and life. The development of solar water heaters has experienced four generations: stuffy dry type, flat type, glass vacuum tube type and heat pipe vacuum tube type.
(2) Solar energy collects heat to generate electricity. Solar thermal power generation, also called solar thermal power generation, is one of the focuses in the field of solar energy utilization in the world today. The principle of solar heat collection power generation is very simple, that is, the solar collector collects the high temperature generated by solar radiation to replace the conventional boiler or drive the Stirling generator to generate electricity. Compared with traditional power plants, solar thermal power plants have two advantages: the whole power generation process is clean and there is no carbon emission from Jehol; The use of solar energy has no fuel cost. Solar thermal power generation requires high heat collection temperature, so it is generally necessary to use focused heat collectors to improve the light energy flow density.
At present, there are three main types of solar thermal power generation systems: slot line focusing system, tower system and dish system. Trough system uses parabolic trough mirror to focus the sunlight on the tubular receiver, and the heat transfer working medium in the heating pipe generates steam to drive the conventional steam turbine to generate electricity. The tower system uses an independent heliostat to track the sun and focus the sunlight on the receiver fixed at the top of the tower, resulting in high temperature. Dish system is a parabolic reflector composed of many mirrors. The receiver is at the focus of the paraboloid, and the heat transfer working medium in the receiver is heated to about 750℃ to drive the engine to generate electricity.
2. Solar photovoltaic power generation Solar photovoltaic power generation is a new type of power generation method that directly converts solar radiation energy into electric energy by using the photovoltaic effect of solar cell semiconductor materials. There are two kinds of power generation systems: independent operation and grid-connected operation. Independent photovoltaic power generation system needs storage battery as energy storage device, which is mainly used in remote areas without power grid and scattered population areas, and the whole system cost is very high; In areas with public power grid, photovoltaic power generation system connected to the power grid can save batteries, which not only greatly reduces the cost, but also has higher power generation efficiency and better environmental protection performance.
Photovoltaic power generation system is mainly composed of solar cell module, controller and inverter. Among them, solar cell module is the core part of the whole power generation system and the most valuable part of the solar power generation system. Its function is to convert solar energy into electric energy or send it to a storage battery for storage. The quality and cost of solar panels will directly determine the quality and cost of the whole system. The function of solar controller is to control the working state of the whole system and protect the battery from being overcharged and discharged. In places with large temperature difference, qualified controllers should also have temperature compensation function. In addition, light-controlled switch and time-controlled switch light are common functions of the controller. The main function of inverter is to convert the low-voltage DC directly output by solar energy into usable alternating current.
Solar cell is the basic component of photovoltaic power generation system and the source of its power generation. Its principle is to generate free charges in some specific semiconductors under the irradiation of sunlight. The directional movement of these free charges accumulates and generates a certain electromotive force, which can provide current for external circuits. This phenomenon is called photovoltaic effect or photoelectric effect, which is the physical basis for manufacturing solar cells.
As the core of the whole solar photovoltaic industry chain, commercial solar cells mainly include the following types: monocrystalline silicon cells, polycrystalline silicon cells, amorphous silicon cells, cadmium telluride cells, copper indium selenium cells and so on. At present, polysilicon thin films and organic solar cells are also being studied. But as far as practical application is concerned, the thin film technology represented by monocrystalline silicon, polycrystalline silicon and amorphous silicon is the main one.
3. Hydrogen production from solar energy belongs to secondary energy and new energy. It is clean and non-toxic, pollution-free to the environment and widely used. At present, the methods of using solar energy to decompose water to produce hydrogen are: solar energy to decompose water to produce hydrogen, solar energy to generate electricity to electrolyze water to produce hydrogen, photocatalytic water to produce hydrogen, solar energy to produce hydrogen and so on.
4. Solar buildings use solar energy for power supply, heating, refrigeration and lighting, which is a new development direction of solar energy utilization.
The development of solar buildings can be roughly divided into three stages: the first stage is "passive solar house", which is a building that collects, stores and distributes solar energy completely through the structure, orientation and layout of buildings and the application of related materials; The second stage is "active solar house", which is a building with solar collector and air conditioning heating system; The third stage is the application of solar cells to provide heating, air conditioning, lighting and electricity for buildings, which can fully meet these requirements. It is called "zero-energy-consumption residence", and its typical use is photovoltaic building integration.
Photovoltaic Building Integration (BIPV) is the perfect combination of solar photovoltaic and building, and belongs to distributed power generation.
5. Other forms of solar energy ① Solar cars. Solar cars use solar cells to convert solar energy into electric energy, and use this electric energy as the energy to drive cars.
② Solar seawater desalination. Compared with the existing seawater desalination system, the solar seawater desalination system has many advantages: it can operate independently, is not limited by steam, electricity and other conditions, has no pollution, low energy consumption, low emission, safe, stable and reliable operation, and has outstanding application value; Flexible production scale, strong adaptability, relatively less investment and lower cost.
Wind power generation technology The utilization of wind energy is mainly wind power and wind power generation, among which wind power generation is the main one. Taking wind energy as power means using wind to directly drive various mechanical devices, such as driving a water pump to lift water.
The main utilization ways of wind energy are: wind power generation, wind-driven water lifting, sail-assisted navigation, wind-driven heating and so on.
1, horizontal axis wind turbine technology Because horizontal axis wind turbine has the advantages of high wind energy conversion efficiency, short rotating shaft and more prominent economy in large wind turbines, it has become the mainstream model of wind power development in the world and occupies more than 95% market share. At present, the vertical axis wind turbine developed in the same period has a small market share and a limited number of applications due to problems such as too long rotating shaft, low wind energy conversion efficiency, and difficulty in starting, stopping and pitching. However, due to its advantages of omni-directional wind direction, speed change device and generator can be placed under the wind wheel (or on the ground), the relevant international research and development has been carried out continuously and made some progress in recent years.
2. The single capacity of wind turbines has been continuously increased, and the utilization efficiency has been continuously improved. In recent years, the single capacity of wind turbines in the world wind power market has continued to increase. The mainstream models in the world increased from 500~ 1000 kw in 2000 to 2~3 MW in 2004. At present, the maximum single unit capacity of wind turbines in operation in the world is 5 MW, and the design and development of 10 MW wind turbines have begun.
3. Offshore wind power generation technology has become the development direction. At present, the cost of building offshore wind farms is 1.7 ~ 2 times that of onshore wind farms, and the power generation is 1.4 times that of onshore wind farms, so its economy is still not as good as that of onshore wind farms. With the continuous development of technology, the cost of offshore wind power will continue to decrease, and its economy will gradually become prominent.
4. Variable pitch speed and power regulation are widely used. Because of the advantages of stable load control, safety and high efficiency, variable pitch power regulation has been widely used in large wind turbines this year.
5. The technology of direct drive and full power converter has developed rapidly. The direct connection mode without gearbox can effectively reduce the unit failures caused by gearbox problems, effectively improve the operation reliability and life of the system, and reduce the maintenance cost, so it is favored by the market and its market share is expanding.
6. The new vertical axis wind turbine adopts a completely different design concept, adopts a brand-new structure and materials, and achieves excellent performance such as prestige start, no noise, typhoon resistance 12 or above, and is not affected by wind direction, which can be widely used in small and medium-sized applications such as villas, multi-storey buildings and street lamps. The wind-solar hybrid power generation system based on it has the advantages of stable output power, high economy and little impact on the environment, and also solves the impact on the power grid in solar energy development.
Hydroelectric power generation technology Hydroelectric power generation is one of the main energy sources in the world, providing about 1/5 of the world's electricity, accounting for 95% of the renewable energy generation. Compared with other energy sources, 33% of hydropower resources have been developed, and the remaining 90% of undeveloped hydropower resources are in developing China countries. Hydropower is very cheap and sustainable, so it is very important to solve the problem of climate and energy supply, especially for developing countries with economic transformation. At present, China is the country with the largest hydropower utilization in the world, with a total installed capacity of 1 17000 MW and an annual power generation of 40 1200 GWh. The Three Gorges Hydropower Station is the largest hydropower station in the world.
The research and development of biomass energy technology 1, direct-fired biomass direct combustion and curing molding technology mainly focus on the design of special combustion equipment and the application of biomass molding. According to the shape of molded products, the developed molding technologies can be divided into three categories: screw extrusion technology developed by Japan, cylindrical block molding technology developed by piston extrusion in European countries, and particle molding technology and equipment developed by the United States.
2. Biomass gasification Biomass gasification technology is to heat solid biomass in a gasifier and introduce air, oxygen or steam at the same time to generate high-grade combustible gas. Its characteristics are that the gasification rate can reach more than 70% and the thermal efficiency can reach 85%. The combustible gas produced by biomass gasification can be used for synthesis, heating, power generation and other different purposes after treatment, which is of great significance to remote mountainous areas rich in biomass raw materials, which can not only change their quality of life, but also improve energy efficiency and save energy.
3. Liquid biofuels Liquid fuels made from biomass are called biofuels. Biofuels mainly include bio-ethanol, bio-butanol, bio-diesel and bio-methanol. Although the production of liquid fuel from biomass started earlier, it developed slowly. Influenced by the world oil resources, price, environmental protection and global climate change, many countries have paid more and more attention to the development of biofuels since 1970s, and achieved remarkable results.
4. Biogas Biogas is a kind of combustible gas produced by microbial fermentation under the conditions of isolated air (reduction) and suitable temperature and humidity. Methane, the main component of biogas, is similar to natural gas and is an ideal gas fuel. Colorless and odorless, it can burn after being mixed with proper amount of air.
① Traditional utilization and comprehensive utilization technology of biogas.
China is a country that develops more biogas in the world. At first, it was mainly rural household biogas digesters to solve the problems of straw burning and insufficient fuel supply. Later 1936 started large and medium-sized biogas projects. Since then, large and medium-sized wastewater, aquaculture wastewater, rural biomass waste and urban garbage biogas have come out one after another, broadening the scope of biogas production and use.
Since 1980s, biogas fermentation comprehensive utilization technology, which takes biogas as a link to realize multi-level utilization of materials and rational flow of energy, has gradually become an effective method to promote the sustainable development of rural areas in China. Through the comprehensive utilization technology of biogas fermentation, biogas is used for farmers' living energy and the production and processing of agricultural and sideline products, biogas slurry is used to produce feed, biological pesticides and culture solution, biogas residue is used to produce fertilizer, the "four-in-one" biogas ecological agriculture model of plastic greenhouse, biogas digester, gas poultry house and toilet promoted in the north, the ecological orchard model with biogas as the link in the central region, and the "pig fruit" model established in the south. As well as the models of "farming-biogas", "pig-biogas-fish" and "grass-cow-biogas" established in other areas according to local conditions, all of them are eco-agricultural models with agriculture as the leader, biogas as the link, and biogas, biogas slurry and biogas residue being utilized at multiple levels. The establishment of an eco-agricultural model for comprehensive utilization of biogas fermentation, which closely combines rural biogas with agricultural ecology, is an effective measure to improve rural environmental sanitation, an effective way to develop green planting and aquaculture, and a new growth point of rural economy.
② biogas power generation technology
With the continuous development of large-scale biogas digester construction and comprehensive utilization of biogas, biogas utilization technology appeared when biogas was burned to generate electricity. It uses biogas produced by anaerobic fermentation on the engine and is equipped with a comprehensive power generation device to generate electric energy and heat energy. Biogas power generation has the characteristics of high efficiency, energy saving, safety and environmental protection, and it is a widely distributed and low-cost distributed energy source. Biogas power generation has been widely valued and actively promoted in developed countries. In some western European countries, the grid-connected electricity of biomass power generation accounts for about 10% of the total energy.
③ biogas fuel cell technology
Fuel cell is a device that directly converts chemical energy stored in fuel and oxidant into electrical energy. When fuel and oxidant are continuously supplied to the fuel cell from the outside, it can continuously generate electricity. According to different electrolytes, fuel cells can be divided into alkaline fuel cells (AFC), proton exchange membranes (PEMFC), phosphoric acid (PAFC), dissolved carbonate (MCFC) and solid oxide (SOFC).
Fuel cells have the advantages of high energy conversion efficiency, cleanliness, no pollution and low noise. It can provide centralized power supply or decentralized power supply. It is one of the most competitive, efficient and clean power generation modes in 2 1 century. It has broad application prospects and huge potential market in clean coal-fired power stations, electric vehicles, mobile power supplies, uninterruptible power supplies, submarines, space power supplies and so on.
5. Bio-hydrogen production Hydrogen is a clean and efficient energy source, which has a wide range of industrial uses and great potential. In recent years, the research of biological hydrogen production has gradually become the focus of attention, but it is not easy to convert other substances into hydrogen. The process of biological hydrogen production can be divided into two categories: anaerobic photosynthetic hydrogen production and anaerobic fermentation hydrogen production.
6. Biomass power generation technology Biomass power generation technology is a technology that converts biomass energy into electric energy, mainly including agricultural and forestry waste power generation, garbage power generation and biogas power generation. As a kind of renewable energy, biomass power generation has been paid more and more attention in the world, and it has been paid more and more attention by the government and supported by the people in China.
Biomass power generation will collect, process and sort out abandoned agricultural and forestry residues to form commodities, prevent environmental pollution caused by straw burning in the field and change the appearance of villages, which is one of the energy strategic choices for building ecological civilization and sustainable development in China. If China's biomass energy utilization reaches 500 million tons of standard coal, it can solve more than 20% of China's current energy consumption, reduce the carbon content in carbon dioxide emissions by nearly 350 million tons every year, and reduce the emissions of sulfur dioxide, nitrogen oxides and soot by nearly 25 million tons, which will produce huge environmental benefits. More importantly, China's biomass energy resources are mainly concentrated in rural areas. Vigorously developing and utilizing the abundant biomass energy resources in rural areas can promote the development of rural production, significantly improve the rural appearance and living conditions of residents, and will have a positive and far-reaching impact on building a new socialist countryside.
Nuclear power generation technology Nuclear power generation uses the heat generated by nuclear fission reaction of uranium fuel to heat water to high temperature and high pressure. The heat released by nuclear reaction is much higher than the energy released by burning fossil fuels, but the amount of fuel required is far less than that of thermal power plants.
Throughout the history of nuclear power development, the technical scheme of nuclear power plants can be roughly divided into four generations.
The first generation of nuclear power plants. The development and construction of nuclear power plants began in the 1950s. 1954, the former Soviet union built an experimental nuclear power plant with a power generation capacity of 5 MW;
1957, the United States built a prototype nuclear power plant in Shiping Port with a power generation capacity of 90,000 kilowatts. These achievements prove the technical feasibility of using nuclear energy to generate electricity. Internationally, the above experimental prototype nuclear power unit has become the first generation nuclear power unit.
Second generation nuclear power plant. At the end of 1960s, on the basis of experimental and prototype nuclear power units, nuclear power units such as pressurized water reactor, boiling water reactor, heavy water reactor and graphite water-cooled reactor with power generation capacity of 300,000 kilowatts were successively built. They further proved the feasibility of nuclear power generation technology and the economy of nuclear energy. At present, most of the more than 400 nuclear power units that have been put into commercial operation in the world are short for this period and are customarily called the second generation nuclear power units.
Third generation nuclear power plant. In 1990s, in order to eliminate the negative effects of the accidents at Three Mile Island and Chernobyl, the nuclear power industry concentrated on preventing and alleviating serious accidents. The United States and Europe successively issued the User Requirements Document for Advanced Light Water Reactor (URD Document) and the User Requirements for European Light Water Reactor (EUR Document), which further clarified the requirements for preventing and mitigating serious accidents and improving safety and reliability. Internationally, nuclear power units that meet the URD document or EUR document are usually called the third generation nuclear power units. The requirement of the third generation nuclear power unit is that it can be built for commercial use 20 10 years ago.
The fourth generation nuclear power plant. From June, 5438 to October, 2000/kloc-0, at the initiative of the US Department of Energy, the United States, Britain, Switzerland, South Africa, Japan, France, Canada, Brazil, South Korea, Argentina and other countries interested in developing nuclear energy jointly formed the "Fourth Generation International Nuclear Energy Forum", which was held in July, 2006.
Geothermal energy technology is the best way to utilize high-temperature geothermal resources. Geothermal energy of 200~400℃ can be directly used to generate electricity.
Steam geothermal power generation is to directly introduce the dry steam from steam field into the steam turbine generator set for power generation, but before the steam is introduced into the generator set, the cuttings and water droplets contained in the steam should be separated. This power generation method is the simplest, but the dry steam geothermal resources are very limited, and most of them exist in deep strata, so it is difficult to mine, so its development is limited. There are mainly two kinds of power generation systems: back pressure type and condensed gas type.
1, hot water geothermal power generation ① flash system
When high-pressure hot water is pumped from the hot water well to the ground, due to the pressure drop, part of the hot water boils and "flashes" into steam, which is sent to the steam turbine to do work; The separated hot water can be discharged after continuous utilization, and it is of course best to re-inject it into the formation.
② Dual-cycle system
Geothermal water first flows through the heat exchanger, transferring geothermal energy to another low-boiling working fluid, boiling it and generating steam. Steam enters the steam turbine to do work, then enters the condenser, and then passes through the heat exchanger to complete the power generation cycle. Geothermal water flows back from the heat exchanger and is injected into the ground. The system is especially suitable for geothermal resources with high salt content, strong corrosiveness and high non-condensable gas content. The key technology of developing dual-cycle system is to develop high-efficiency heat exchanger.
2. When the high-grade energy of coal, oil and natural gas is used for geothermal heating and the boiler is turned into low-grade hot water heating, it is a waste of energy and brings serious air pollution. It is best to use low-temperature geothermal resources with higher temperature (below 90℃) for geothermal heating.
① Conventional geothermal heating
Iceland uses underground hot water above 90℃ to realize 0/00% geothermal heating in Reykjavik, the capital, and 90% geothermal heating in the whole country. It is a model of geothermal heating and the only smoke-free city in the world. Tianjin geothermal heating area accounts for more than 70% of the country, and Tianjin is rich in geothermal resources at 80℃ underground. Underground hot water can be directly sent to the radiator system for heating. A single well can produce more than 2,000 cubic meters of hot water day and night, which can provide heating for a building area of 6,543,800 square meters. After the first cycle, the temperature of underground hot water is reduced to 40~48℃, which can also be used for floor heating, and the heating can be expanded by 20 ~ 40 thousand square meters.
② Ground source heat pump heating
In Tianjin, the secondary backflow of geothermal water is used for floor heating (30~35℃), and then the heat pump is used to extract heat, and the heating capacity of a single well can be expanded by 50 ~ 60 thousand square meters.
③ Geothermal greenhouse planting
Using geothermal heating greenhouse, or even using warm water of about 30℃ to heat the soil, can implement geothermal greenhouse planting, produce high-grade anti-season fresh vegetables in winter, and produce bananas, oranges and high-grade flowers in northern geothermal greenhouse, which can meet the consumption needs of hotels, tourism and people's lives and create higher economic benefits.
④ Geothermal aquaculture
The advantages of geothermal culture are: prolonged culture time in a year, high-density culture of special fish, and increased yield of adult fish per unit water area.
Ocean energy technology 1, tidal energy The tidal phenomenon caused by the change of lunar gravity leads to the periodic rise and fall of sea level. The energy generated by seawater fluctuation and tidal flow is called tidal energy. The main utilization mode of tidal energy is power generation. According to the estimation of the World Power Congress, by 2020, the global tidal power generation will reach 654.38+00 billion to 300 billion kilowatts. The largest tidal power station in the world is the rance river Power Station on the English Channel in northern France, with a power generation capacity of 240,000 kilowatts, which has been in operation for more than 30 years. The largest tidal power station in China is Jiangxia experimental tidal power station with a total capacity of 3000 kilowatts.
2. Wave energy Wave energy refers to the kinetic energy and potential energy of waves on the ocean surface. It is a kind of mechanical energy generated by wind and stored by short-period waves in the form of potential energy and kinetic energy. The energy of waves is proportional to the square of wave height, the period of wave motion and the width of wave front. Wave energy is one of the most unstable marine energy sources.
Wave power generation is the main way to use wave energy. In addition, wave energy can also be used for pumping water, heating, seawater desalination and hydrogen production.
3. Seawater temperature difference energy Seawater temperature difference energy refers to the heat energy generated by the water temperature difference between surface seawater and deep seawater, and is an important form of ocean energy. In low latitudes, the sea surface water temperature is high, and there is a temperature difference with the deep cold water. The heat energy is stored by the temperature difference, and its energy is proportional to the temperature difference and water quantity. The main utilization mode of temperature difference energy is power generation.
4. Seawater permeability If there are two kinds of salt solutions: one is that the salt concentration in the solution is high, and the other is that the salt concentration in the solution is low. Then the two solutions are put together and separated by osmotic membrane, which will produce osmotic pressure and water will flow from the solution with low salt concentration to the solution with high salt concentration. What flows in rivers is fresh water, and what exists in the ocean is salt water, and there is also a certain concentration difference between them. If a turbine generator is placed in the estuary, the osmotic pressure between fresh water and seawater can push the turbine to generate electricity. Infiltration energy is a kind of renewable energy with the largest energy density in ocean energy.