What is wind energy?

main content:

  1. 1 How the wind is formed
  2. 2 "Catch" the gale

Wind is one of the natural phenomena that mankind is most familiar with. When a tree is uprooted by a strong wind and a huge wave raised by a hurricane even submerges a New Orleans city, people will marvel at the power of the wind. That is an extreme situation. The usual wind also has energy and can be exploited and utilized by humans as an energy source.

1 How the wind is formed

How the wind is formed

The wind is caused by the heat of the sun. When the sun shines on the surface of the earth, the heat and heat are different everywhere, which creates a temperature difference, which causes the convective movement of the atmosphere and forms the wind. The cold air with higher air pressure flows to the hot air area with lower air pressure, and the hot air flows to the cold air area at the same time to supplement the atmosphere. The poet's eloquent phrase "the sky is rolling and the cold current is swift, and the earth is slightly heated" is a vivid portrayal of the wind. Located in the northern hemisphere, the north wind is strong in winter, and the south wind is cool in summer, which is the result of the polar air current flowing to the equator. In coastal areas, there is sea breeze during the day and land breeze at night; in mountainous areas, there is valley breeze during the day and mountain breeze at night. These are winds with different wind directions due to changes in temperature due to the influence of terrain. These winds can all use their energy. The energy of the wind depends on the wind speed and has nothing to do with the wind direction. The higher the wind speed, the more energy the wind contains. The wind is not as stable as flowing water, but changeable. The wind is often buzzing, big and small, which is a common feeling among people. Generally, the higher the wind, the higher the wind speed. The space within 10 meters above the ground is called the ground boundary layer by meteorology as the most suitable space for wind energy development. Because the density of air is very small, which is 1/813 of the density of water, the energy density of wind is also small. As far as the ground area is concerned, 150 to 300 watts square meters is not bad. Therefore, people try to increase the height of the wind turbine as much as possible to "capture" a greater wind speed in order to obtain more wind energy. People use wind as a natural resource, but wind can sometimes cause natural disasters. In order to gain advantages and avoid disadvantages, it is necessary to carefully study the characteristics and changes of wind and grasp the customs.

Schematic diagram of sea and land breeze environment

Schematic diagram of sea and land breeze environment

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Wind energy is a kind of kinetic energy, which can be calculated with the formula of kinetic energy:

What is wind energy

In the formula, E is the kinetic energy of the movement of the object, m is the mass of the moving object, and v is the movement speed.
Since air is a fluid, only part of the energy is captured when the kinetic energy of the wind acts on the wind turbine, and the rest is lost. We can use the kinetic energy density of the wind per unit area to calculate the energy of the wind, so as to grasp the way to use wind energy.
If P is used to represent the wind energy density (E/m²) per square meter (m²) and ρ is the density of air (M/m³), the mass of air flowing per square meter area per unit time is ρν. Then, the wind energy density can be expressed as follows:

What is wind energy

The unit of wind energy density is expressed by the power per unit area (W/m²). It can be seen that the wind energy density is proportional to the third power of the wind speed. Obviously, the greater the wind speed, the greater the energy density of the wind, and the more wind energy the wind turbine can obtain. Therefore, wind turbines should be installed in places with high wind speeds, and a large windward area can obtain more wind energy.


People have designed a graphic to depict the distribution of wind direction and wind speed in a certain place over a period of time, called the "wind rose diagram" because it resembles a blooming rose. The most common wind rose diagram is a circle. 16 rays are drawn from the circle, representing 16 different directions of wind. The length of each ray represents the frequency of wind in that direction, which is 100% of the static wind. The frequency of wind is written in the middle. The icons indicate the range of wind speed in each direction and its percentage. In this way, the wind rose chart contains three data of wind direction, wind frequency and wind speed, which is very convenient and intuitive to use. Of course, these data are obtained through long-term scientific observations. The wind map reflects the variability of the wind, but this change is not impermanent. A certain place always has its dominant wind in a certain period of time.

Wind rose illustration

Wind rose illustration

How much wind energy is there in the world? Wind energy resources can be said to be very rich, both on land and on the sea. If the land with a wind speed greater than 5.0 m/s is used as a wind power plant, there are 30 million square kilometers of this land in the world, which accounts for 28% of the total land area of ​​the world. The installed capacity of this type of wind farm can reach 8,000 kilowatts per square kilometer, and the above-mentioned total land-based installed capacity will reach 240 billion kilowatts. Obviously, this is only a theoretical figure. There are many other uses for this part of the land, and it is impossible to use all of it as a wind farm. Assuming that the area used for a wind farm is 1% to 2% of it, that is not a lot. In terms of power generation, even if the utilization rate of wind turbines is only half (calculated by about 4000 hours of full-load operation per year), the annual power generation can reach 20 trillion kilowatt-hours, which is equivalent to 4 times the world's total electricity consumption in 2000. It is also equivalent to half of the total energy consumption of the year (9 billion tons of oil equivalent), which can support half the sky.

The above is for large-scale interconnected wind farms. In fact, there are more land areas with an average annual wind speed of 3 to 5 meters per second, accounting for about half of the global land area. These places can be installed with small wind generators and wind pumps, which is also an economical way of using wind energy, which is suitable for on-site utilization in many areas. Offshore wind resources are more abundant, about 3 to 5 times the resources on land. With the advancement of technology, the development of offshore wind energy will also increase, and it will be compared with the use of wind energy on land.

2 "Catch" the gale

Catch the gale

The use of wind energy has a long history and has already begun in ancient times. As early as several centuries BC, the Chinese would use wind energy to lift water, irrigate, and grind spring rice, and use sails to propel ships. In the 1st century AD, wind turbines have appeared and are widely used in the Middle East. In the 13th century, wind turbines were introduced to Europe and became an indispensable prime motive in Europe. After the industrial revolution in the 18th century, especially in the 20th century, the utilization of wind energy showed a downward trend due to the development and application of coal, oil and natural gas. It was not until the occurrence of the energy crisis in the mid-1970s that it aroused people's renewed attention to the development of wind energy. In recent years, wind power generation has made considerable progress. Countries such as Germany, the United States, Spain, and Denmark are leading the way. Large-scale wind turbines are more than self-sufficient and export large quantities. At present, the contribution rate of wind power to the world's electricity is still very small, but as a clean energy and renewable energy, wind energy is generally favored by all countries, and its development is rapid. It is estimated that by 2020, the global wind power generation capacity will exceed 400 million kilowatts.

China has a wide range of wind energy resources. The theoretical resource on land is about 1.6 billion kilowatts, and the known usable amount is about 250 million kilowatts. With the advancement of technology, the amount that can be developed may also increase exponentially. China's wind energy resources are second only to the United States and Russia, ranking third in the world. They are mainly distributed along the eastern coast and islands, and inland along the northeast, Inner Mongolia, Gansu and Xinjiang. The average wind energy density in these places is 150-300 watts/square meter, and the effective wind speed exceeds 3 meters/second for 4000-8000 hours in a year, which is a place with abundant wind energy resources. China's wind power development is also very fast. Since the first wind farm was built in Rongcheng, Shandong in 1986, wind farms have sprung up like bamboo shoots in various places, each becoming larger and larger. Typical wind farms, such as Nan'ao Island Wind Farm and Dabancheng Wind Farm, have achieved successful experiences. Guangdong Nan'ao Island is located at the mouth of the Taiwan Strait, known as the wind island. The annual average wind speed is 8.5 meters per second, and the effective wind speed is 7000 hours a year. The first-phase installed capacity of the wind farm is 50,000 kilowatts and has been operating normally. The short-term installed capacity is 200,000 kilowatts, and the long-term installed capacity will reach 600,000 kilowatts, which is full of development potential. Dabancheng in Xinjiang is located in the vents of the Junggar Basin and Turpan Basin. It has the best wind resources in mainland China, with an installed capacity of 70,000 kilowatts in the first phase and 2.5 million kilowatts of development potential. The song "The Girl of Daban City" by Wang Luobin, the king of western singers in the past, made this remote area at the foot of the Tianshan Mountains famous all over the country, but now it is not stones and watermelons, but precious clean energy wind power. By 2004, 43 wind farms had emerged across the country with an installed capacity of 760,000 kilowatts; looking forward to 2010, it may reach 40 million kilowatts; in 2030, it may reach 100 million kilowatts. By then, wind power can play a decisive role in power supply.

Wind power plant on Nan'ao Island

Wind power plant on Nan'ao Island

Some people say that in the United States, North Dakota and other three states alone have developed wind power to meet the power needs of 50 states in the country; in densely populated Europe, it is easy to obtain wind power along the coast to meet the power of the entire Europe; in China , Wind power alone can easily double the current national power generation; in the world, as long as 1% of the global land-based wind energy is used, the global total energy needs can be met. These words are not deliberately exaggerated, not too outrageous, but should be encouraging.

However, the use of wind energy has not been smooth sailing.

There are many aspects of wind energy utilization, and power generation is the main utilization aspect, especially for large-scale wind farms. Often dozens or even hundreds of wind turbines are installed in a wind farm to provide electricity to the grid. Become the main development direction of wind power. However, wind energy has the characteristics of low energy density, which is also a shortcoming of wind energy, which brings greater difficulties to the utilization of wind energy. At present, the single-machine power of wind turbines is mostly around 500 kilowatts. In order to obtain more power, wind turbines have a trend of large-scale. Countries are developing megawatt-level wind turbines, the largest of which has reached 5,000 kilowatts. The height of the wind turbines is also increasing, and wind turbines more than 100 meters high have appeared to take advantage of greater wind speeds. Because of this, the investment in the construction of wind farms is relatively large. At present, most of the wind turbines used in wind farms in China are imported, and the price is relatively high. With tariffs, the construction cost per kilowatt of electricity is more than 10,000 yuan, which is more than twice as high as that of thermal power plants, resulting in the cost of wind power. With high levels, wind power has also become a weak product in market competition. On the other hand, the natural conditions where wind farms are mostly located in remote and impoverished areas have the advantage of building wind farms, but their economic strength is relatively weak and there are market risks, which limits the enthusiasm for the development of this new energy to a certain extent.

Faced with the difficulties in the utilization of wind energy, to develop it faster, government support is an indispensable basic condition, which is also proved by the experience of developed countries. In order to promote the development of new energy and renewable energy, China has introduced a renewable energy power generation quota system (RPS) policy. The purpose is to use laws and regulations to ensure fair competition between new and renewable energy and other energy sources. This is a newly introduced policy from abroad, which rigidly stipulates that a certain amount of renewable energy quotas must be included in the energy composition of electricity consumption in a region. Those without or insufficient quotas can be purchased from other places, otherwise they will be punished. This is a market-based macro-control policy with simple operation and management. This system has little impact on consumers. Although areas with insufficient quotas have to purchase high prices from other places, each family pays less than 1 yuan more for electricity per month. For areas that purchase quotas, it not only promotes The region’s enthusiasm for the development and utilization of renewable energy also supports the further development of regions with renewable energy. This policy is undoubtedly good news for the development of wind energy. It should be noted that both the RPS policy and the government's preferential tax support policy are very effective. Every country has gone through this process, and it is only a temporary need. With the advancement of technology and the development of scale, the economic benefits of renewable energy utilization will inevitably increase, and product prices will inevitably decrease and become more competitive. The situation of higher wind power costs and prices will also change, and the feed-in tariff will be comparable to thermal power. The price is comparable.