What is the new hope for the windmill to turn out?

As a primary energy source, wind energy is an available energy provided to human beings due to the work done by air flow. In short, the kinetic energy possessed by air flow is called wind energy. The history of human utilization of wind energy can be traced back to BC. China is one of the earliest countries in the world to develop and utilize wind energy. People in China use wind to lift water, irrigate, grind flour and use sails to propel ships forward. However, after thousands of years, wind technology has developed slowly, which has not attracted enough attention.

however, since the world oil crisis in 1973, conventional energy has been in urgent need. Especially in recent years, with the development of world industrial economy, the sharp increase of population, the infinite rise of human desire and the unrestrained production and lifestyle, the whole world has shown a trend of rapid economic growth and continuous increase of energy consumption. The use of a large number of fossil energy directly leads to more and more serious environmental pollution. In particular, the emission of greenhouse gases, mainly carbon dioxide, has risen sharply, resulting in global warming, reduced snow cover in glaciers, melting icebergs at both poles and obvious rise in sea level, which has caused floods in coastal areas, thus affecting the ecological environment. In this context, how to deal with global warming has become a topic of common concern all over the world and has become one of the great challenges facing all mankind. As a kind of renewable and clean energy, wind energy has great development potential, and it is getting more and more favor, especially for coastal islands, remote mountainous areas with inconvenient transportation, grassland pastures with vast land and sparsely populated areas, rural areas and frontiers that are far from the power grid and are difficult to reach in the near future. Wind energy is of great significance as a reliable way to solve energy sources for production and life (Li Li, 216).

China is located in the southeast of the Asian continent, near the west coast of the Pacific Ocean, with strong monsoon. Monsoon is the basic feature of China's climate. For example, the winter monsoon lasts for 6 months in North China and 7 months in Northeast China, and the southeast monsoon spreads all over the eastern half of China. The total reserve of wind resources in China is 1.6×16MW. Although China's wind power industry started late, based on the support of national policies and funds, it has developed rapidly. So far, China has built several large-scale wind farms in Zhangjiakou, Hebei, Inner Mongolia, Rongcheng, Shandong, Yingkou, Liaoning, Fujin, Dabancheng, Xinjiang, Nan 'ao, Guangdong and Hainan, and plans to build GW-class wind farms in Nantong, Guanyun and Yancheng, Jiangsu.

at present, China has increased its investment in the utilization and development of wind energy, making efficient and clean wind energy utilization occupy its due position in China's energy pattern.

first, the causes and characteristics of wind energy

wind energy is the kinetic energy generated by a large amount of air flowing on the earth's surface, and it is a form of conversion of solar energy. Because of the different temperature changes and the different water vapor content in the air after being irradiated by the sun, the air pressure varies from place to place, and high-pressure air flows to low-pressure areas in the horizontal direction, which forms wind.

a force of .1kN per square meter is blown on the surface of an object by a 5-level wind with a wind speed of 9-1m/s. The force of a 9-level wind with a wind speed of 2m/s on the surface of an object can reach about .5kN per square meter. The wind speed of a typhoon can reach 5 ~ 6m/s, and its pressure on the surface of an object per square meter can reach more than 2.kN. The rough waves are stirred by the wind, and their impact on the coast is extremely great, sometimes even as high as 2 ~ 3 kN per square meter, and even as high as 6kN per square meter. This shows that the energy of the wind is beyond our imagination.

wind energy not only has great energy, but also plays a great role in nature. It can transport water on the surface, and water vapor is mainly transported by strong air flow, which affects the climate and forms rainy season and dry season. The energy in the wind is much higher than the energy that humans have been able to control so far. Compared with other energy sources, wind energy has both obvious advantages and certain limitations. Its characteristics include:

(1) huge accumulation. It is estimated that although only about 2% of the solar energy reaching the earth is converted into wind energy, its total amount is considerable, and the global wind energy is about 2.74×19MW, of which the available wind energy is about 2×17MW, which is 1 times larger than the total amount of water energy that can be developed and utilized on the earth. The energy obtained by burning coal in the world every year is less than 1% of the energy provided by wind to the earth at the same time.

(2) The source is abundant and inexhaustible. Wind is caused by repeated natural cycles and is widely distributed on the earth.

(3) No pollution, clean and harmless. Wind energy itself belongs to clean energy, and the mature wind energy utilization and conversion technology is also environmentally friendly and pollution-free.

(4) low energy density. This is an important defect of wind energy, because wind energy comes from the flow of air, and the density of air is very small, so the energy density of wind energy is also very small. As can be seen from Table 4-2, among all kinds of energy sources, the energy density of wind energy is extremely low, which brings certain difficulties to its utilization.

(5) unstable. The airflow changes frequently, and the pulsation, diurnal variation and seasonal variation of the wind are very obvious, with great fluctuation and seasonal and random characteristics.

(6) There are great regional differences. Due to the change of terrain, the regional difference of wind power is very obvious. The wind power in adjacent areas and favorable terrain may be several times or even dozens of times that in unfavorable terrain.

table 4-2 energy flow density of various energy sources

ii. distribution of wind energy resources in China

China has a vast territory, with a total land area of more than 2, kilometers, a coastline of more than 18, kilometers and more than 5, islands in the marginal sea, which is rich in wind energy resources. The annual average wind speed of existing wind farm sites in China has reached more than 6 m/s. Generally speaking, the wind conditions of wind farms can be divided into three categories: the annual average wind speed is better than 6m/s, 7m/s and 8 m/s. According to the wind speed frequency curve and the power curve of the unit, the annual power generation of the unit under the international standard atmospheric state can be estimated. Our country is equivalent to an area of more than 6m/s, which is only limited to a few areas in the whole country. As far as inland is concerned, it only accounts for about 1/1 of the country's total area, mainly distributed in the southeast coast and its islands between the Yangtze River and Nan 'ao Island. These areas are China's largest wind energy resource areas and rich in wind energy resources, including Shandong, Liaodong Peninsula, the coast of the Yellow Sea, the South China Sea coast west of Nan 'ao Island, Hainan Island and South China Sea Islands, and Inner Mongolia from north of the yinshan mountains to north of Daxing 'anling, Dabancheng, Alashankou, Hexi Corridor, the lower reaches of Songhua River.

iii. Utilization of wind energy

In principle, any object that can generate asymmetric force in the flow of wind can generate rotation, translation or vibration, thus obtaining wind energy. The earliest use of wind energy was sails. At present, wind energy is mainly used in the following aspects.

(1) Wind-driven water lifting

Wind-driven water lifting has a long history as the main way of wind energy utilization. For thousands of years, it has been a simple and practical technology to solve the problems of agricultural irrigation and drainage, drinking water for people and animals in pastoral areas and salt production in pond culture and coastal beaches, especially in many remote areas and coastal islands where the power grid is not as good as it is, which has important practical significance for saving conventional energy, improving the ecological environment and promoting the sustainable development of local economy and society. As early as the Ming Dynasty, Fang Yizhi's "Physics Tips" recorded that "six sails were used to irrigate the fields, and the Huaiyang Sea was used to irrigate the fields", describing the scene when people used sails to drive water trucks to irrigate the fields (Liu Huimin et al., 211).

According to the difference of lift and flow, modern wind-driven water pumping units can be divided into three types (Table 4-3): one type is high-lift and low-flow type, and the diameter of the wind wheel of such units is generally less than 6m, and the lift is 2-1m, which is mainly used to extract underground water in deep wells, and it converts the rotary motion of the wind wheel shaft into the reciprocating linear motion of the piston pump to carry out water pumping operation; The second type is the medium lift and large flow type. The diameter of the wind wheel of this kind of water pump unit is generally 5 ~ 8m, the lift is 1 ~ 2m and the flow rate is 15 ~ 25m3/h, which is mainly used for extracting groundwater. This kind of wind-driven water pump is generally a modern streamlined blade with high efficiency, advanced performance and strong applicability, but its cost is higher than that of the traditional wind-driven water pump. The last type is low-lift and large-flow type. The lift of this type of unit is generally .5 ~ 3m, the flow rate is 5 ~ 1m3/h, and the diameter of the wind wheel of the unit is 5 ~ 7m. It can extract surface water such as river water, lake water or seawater for irrigation and drainage in farmland, salt making in salt field and aquaculture. The power of the wind wheel shaft is transmitted to the water truck or the screw pump through the bevel gear. Generally, the automatic windward mechanism is adopted to adjust the wind direction of the wind wheel, and the wing-counterweight speed regulating mechanism is used for automatic speed regulation.

Table 4-3 Several kinds of wind-driven water pumps commonly used in China and their performance tables (according to Liu Huimin et al., 211)

(II) Sail-assisted navigation

Humans have long used wind energy as the propulsion power of ships. Sailing appeared in ancient Egypt and Babylon before BC, while sailing boats were recorded in China as far back as Qin and Han Dynasties. As early as the early 15th century, the famous Ming Dynasty Zheng He's fleet was a large-scale sailing fleet. By the late 16th century, the large-scale merchant ships and warships powered by sails had become very common in Europe. Until the propeller was used as the propeller and the steam engine appeared, ancient sailing ships gradually withdrew from the historical stage.

Modern windsurfing and ancient windsurfing have completely different usage principles. First of all, ancient windsurfing is assisted by the sail as the main propulsion power, while modern windsurfing is propelled by the engine as the main propulsion power and the sail as the boosting means, which can not only make use of the characteristics of energy saving and environmental protection of windsurfing, but also minimize the environmental restrictions on windsurfing. At present, 1,-ton cargo ships use computer-controlled sails to aid navigation, and the fuel saving rate reaches 15%.

(3) Wind heating

In recent years, people's living standards have been improving day by day, and the demand for heat energy in household energy is increasing, especially in some high-latitude areas, such as Europe and North America, where the energy consumption of heating and boiling water is high. In order to meet the needs of domestic and low-grade industrial heat energy, wind heating has made great progress.

the so-called wind heating is to convert wind energy into heat energy. There are three ways to heat by wind power: first, the wind turbine generates electricity, and then the electric energy is converted into heat energy through resistance wires. Although the efficiency of converting electric energy into heat energy is 1%, the efficiency of converting wind energy into electric energy is very low, so this method is not desirable from the perspective of energy utilization; Second, the wind energy is converted into air compression energy by a wind turbine, and then converted into heat energy, that is, the centrifugal compressor is driven by the wind turbine to adiabatically compress the air and release heat energy; The third is to directly convert wind energy into heat energy with wind turbines (Wang Xi et al., 215). Obviously, the third way has the highest heating efficiency and is therefore the most widely used. There are many ways to directly convert wind energy into heat energy with a wind turbine. The simplest and practical one is to stir the liquid for heating, that is, the wind turbine drives the agitator to rotate, so that the liquid becomes hot. In addition, there are solid friction heating and eddy current heating.

(4) Wind power generation

In recent years, wind power generation has gradually become the main form of wind energy utilization, and all countries have attached great importance to wind power generation, and its development speed is extremely fast.

1. the principle of wind power generation

the principle of wind power generation is to use wind power to drive the windmill blades to rotate, and then increase the rotating speed through the speed increaser to urge the generator to generate electricity (figure 4-4). According to the current windmill technology, power generation can be started at a breeze speed of about 3 m/s. Wind power generation is becoming an upsurge in the world, because wind power generation does not need to use fuel, nor does it produce radiation or air pollution.

figure 4-4 wind turbine

2. forms of wind power generation

1) off-grid applications

there are many off-grid applications of wind turbines, which are mainly divided into the following categories:

(1) charging batteries: most of these applications refer to small wind turbines for a single family residence. Wind turbines with rotor diameter of 3m (power range of 4 ~ 1 W) belong to this category.

(2) provide reliable power for remote areas, including small, unattended wind turbines. Wind turbines are usually connected to storage batteries, and can also be connected to other power sources such as photovoltaic batteries or diesel generators. Typical uses include power supply for maritime navigation equipment and long-distance communication equipment.

(3) Water supply heating: This system is mostly used in private houses. The typical usage is to connect the wind turbine directly to the immersion heater or electric radiation heater.

(4) Other uses in remote areas: including power supply for rural areas, power supply for small power grid systems, and power supply for commercial refrigeration systems and seawater (or brackish water) desalination equipment.

In the application of off-grid generators, the wind generator is the dominant one to charge the battery. The rotor diameter of this kind of wind turbine is usually less than 5m, and its rated power is less than 1W W.

2) networking applications

(1) single wind turbines: these generators can provide electricity for residents, businesses, industries or agriculture. Its electric load is close to the capacity of wind turbines, and it can also be linked to the power grid. In most cases, wind turbines are installed near a farm or a group of residential houses. The power of these wind turbines is generally 1 ~ 1～1kW.

(2) Wind farm: It is a centralized installation, uniform distribution and centralized management of multiple wind turbines by the control center, and the power generated is mainly transmitted through the power grid, not specifically serving a region. The power of these wind turbines is generally 5 ~ 5～5kW.

this decentralized networked wind turbine market is influenced by the national energy policy. The Netherlands, the United States, Denmark and Germany have always allowed individuals to connect private wind turbines to the power grid, and allowed surplus electricity to be sold to local power departments. Now there is a trend of large-scale development.

3. Development status of wind power generation at home and abroad

China is the country with the highest occupancy rate of wind resources in the world, and it is also one of the earliest countries to use wind energy in the world. According to statistics, the total amount of wind energy resources at the height of 1m in China is 3226GW, of which the total amount of land-exploitable wind energy is 253GW. Together with offshore wind energy resources, China can use nearly 1GW of wind energy resources. If the development rate of wind energy resources reaches 6%, only wind energy generation can support all the current power demand in China.

however, wind power generation started late in China. Compared with the developed countries of wind power generation in the world (such as Germany, America, Spain, etc.), there is still a big gap. Up to now, China has built a number of large-scale wind farms in Zhangjiakou, Hebei, Inner Mongolia, Rongcheng, Shandong, Yingkou, Liaoning, Fujin, Dabancheng, Xinjiang, Nan 'ao, Guangdong and Hainan, and plans to build 1 billion watt wind farms in Nantong, Guanyun and Yancheng, Jiangsu. According to relevant data, by the end of 23, the global installed capacity of wind power generation has exceeded 4×14kW, and wind power generation accounts for .5% of the global power supply. By the end of 213, the cumulative installed capacity of global electricity reached 3.18×15MW, and the global wind power market expanded by almost 2×15MW from 29 to 213. However, in 213, the installed capacity of wind power increased by 3.55×14MW, which was about 14MW lower than that in 212. In April 214, the cumulative installed capacity of global wind power has reached 3.654×15MW, up 14.9% year-on-year. add