Advantages of wind power generation:
1. Clean and good environmental benefits;
2. Renewable and never exhausted;
3 , Short infrastructure construction cycle;
4. Flexible installed capacity scale.
Disadvantages of wind power generation:
1. Noise, visual pollution;
2. Occupying large areas of land;
3. Unstable, Uncontrollable;
4. The current cost is still very high.
5. Impact on birds.
1. Concept
Wind power generation converts the kinetic energy of wind into electrical energy.
As a clean and renewable energy, wind energy has attracted more and more attention from countries around the world. Its potential is huge. The global wind energy is about 2.74×10^9MW, of which the available wind energy is 2×10^7MW, which is 10 times larger than the total amount of water energy that can be developed and utilized on the earth.
Wind has been used by people for a long time-mainly through windmills to pump water, grind flour, etc., but now, people are interested in how to use wind to generate electricity.
2. Resources
my country is rich in wind energy resources. The exploitable wind energy reserves are about 1 billion kW, of which the wind energy reserves on land are about 253 million kW (10m above the ground on land). Data calculation), the offshore wind energy reserves that can be developed and utilized are about 750 million kW, with a total of 1 billion kW. By the end of 2003, the country's installed electricity capacity was approximately 567 million kW.
Wind is one of the pollution-free energy sources. And it is inexhaustible. For coastal islands, grassland pastoral areas, mountainous areas and plateau areas that are short of water, fuel and have inconvenient transportation, the use of wind power to generate electricity according to local conditions is very suitable and has great potential. Offshore wind power is an important field for the development of renewable energy, an important force in promoting wind power technological progress and industrial upgrading, and an important measure to promote the adjustment of energy structure. my country is rich in offshore wind energy resources. Accelerating the construction of offshore wind power projects is of great significance for promoting atmospheric haze control, adjusting energy structure and transforming economic development methods in coastal areas.
3. Types
Overview
Although there are many kinds of wind turbines, they can be summarized into two categories: ① Horizontal axis wind turbines, wind turbines The rotation axis of the wheel is parallel to the wind direction; ② Vertical axis wind turbine, the rotation axis of the wind wheel is perpendicular to the ground or the direction of the air flow.
1. Horizontal axis wind turbine
Horizontal axis wind turbines are divided into two types: lift type and drag type. Lift-type wind turbines rotate quickly, while drag-type wind turbines rotate slowly. For wind power generation, lift-type horizontal axis wind turbines are mostly used. Most horizontal-axis wind turbines have wind-facing devices that can rotate as the wind direction changes. For small wind turbines, this wind-facing device uses a tail rudder, while for large wind turbines, a transmission mechanism composed of wind direction sensing elements and servo motors is used.
A wind turbine whose wind rotor is in front of the tower is called an upwind wind turbine, and a wind turbine whose wind rotor is behind the tower is called a downwind wind turbine. There are many styles of horizontal axis wind turbines. Some have rotors with counter-rotating blades. Some have multiple rotors installed on one tower to reduce the cost of the tower under certain conditions of output power. Some have horizontal axis wind turbines. Axial wind turbines create vortices around the rotor, concentrating airflow and increasing airflow speed.
2. Vertical axis wind turbine
Vertical axis wind turbine does not need to face the wind when the wind direction changes. This is a major advantage over horizontal axis wind turbine. , which not only simplifies the structural design, but also reduces the gyroscopic force of the wind wheel against the wind.
There are several types of vertical-axis wind turbines that use resistance to rotate. Among them are wind wheels made of flat plates and quilts, which are a pure resistance device; S-type windmills, which have partial lift, but It's mainly a resistance device. These devices have large starting torque, but low tip speed ratio, and provide low power output when the size, weight and cost of the wind wheel are certain.
3. The Darrieux-type wind wheel
was invented by French G.J.M. Darrieux in the 1830s. In the 1970s, the Canadian National Academy of Sciences conducted extensive research on this, and it is now the main competitor for horizontal axis wind turbines. The Darrieux wind wheel is a lift device. The profile of the curved blades is an airfoil. Its starting torque is low, but the tip speed ratio can be very high. For a given weight and cost of the wind wheel, it has a high power output. .
There are many kinds of Darrieux wind turbines, such as Φ type, Δ type, Y type and H type. These rotors can be designed as single blade, double blade, three blade or multi-blade.
4. Doubly-fed induction generator
With the development of power electronics technology, double-fed induction generators (Double-Fed Induction Generator) are increasingly used in wind power generation. The wider. This technology does not rely too much on the capacity of the battery, but starts from the excitation system and appropriately controls the excitation current to achieve the purpose of outputting a constant frequency of electrical energy. The structure of the doubly-fed induction generator is similar to the asynchronous generator, but the excitation of the doubly-fed induction generator uses AC excitation. We know that a pulsating magnetic potential can be decomposed into two rotating magnetic potentials in opposite directions, and the appropriate arrangement of the three-phase windings can eliminate the effect of one of the magnetic potentials, so that a magnetic potential rotating in space is obtained. It is equivalent to the rotor with DC excitation in a synchronous generator. The advantage of the doubly-fed generator is that the frequency of the AC excitation is adjustable, which means that the frequency of the rotating excitation magnetomotive force is adjustable. In this way, when the speed of the prime mover is uncertain, the frequency of the excitation current can be appropriately adjusted to meet the purpose of outputting constant frequency electric energy. As the capacity of power electronic components is getting larger and larger, the excitation system adjustment capability of the doubly-fed generator set is also getting stronger and stronger, which allows the single-machine capacity of the doubly-fed generator to be increased. Although some theories are still being improved, the trend of widespread application of doubly-fed reaction generators will become increasingly obvious.
Wind power generation is not in line with national conditions. Most of the wind power plants that have been launched in China are image projects. Miao Wei, Vice Minister of the Ministry of Industry and Information Technology, recently made shocking remarks. He believed that China is still surrounded by wind and sand, and wind power equipment is severely damaged by wind and sand. Too many wind power projects being launched are inconsistent with my country's national conditions. Miao Wei said that there is no sand in windy places abroad, such as ocean wind. Miao Wei said: In China, wherever there is wind, there is sand. Wind and sand cause severe wear and tear on wind power generation equipment. Nowadays, wind power generators should have a life span of 20 years, but if there is erosion from wind and sand, the life span will not reach 20 years. In another five years, there will definitely be problems with the lifespan, especially for the typical image project of the multi-million-kilowatt wind power station in Gansu. On this topic, Miao Wei said that the focus of energy layout should be to achieve a balance between the supply side and the user side. The current situation is that high-level energy drives low-level energy. For example, Miao Wei said that Hubei originally has an advantage in hydropower, so more electricity from the Three Gorges should be kept in Hubei for use. This is the best clean energy. But now Hubei's electricity is transported to the eastern region, and Hubei then buys coal from surrounding areas and transports it to Hubei. This triggers a series of effects. Henan does not have enough, and coal is transported to Shanxi, Shandong and even Xinjiang. On a grand tour across the country, half of the nation's rail freight was used to transport coal. What a huge logistics cost and waste. According to reports, the 10-million-kilowatt wind power base in Jiuquan, Gansu was fully launched in August 2008, marking that China has officially entered the stage of building the Three Gorges Wind Power Project. According to the latest wind energy assessment results from the meteorological department, Jiuquan’s total wind energy resource reserves are 150 million kilowatts, with a developable capacity of more than 40 million kilowatts and an usable area of ??nearly 10,000 square kilometers.
5. Magnus effect wind wheel
The Magnus effect wind wheel is composed of a spinning cylinder. When it works in the air flow, it moves The force is due to the Magnus effect and its magnitude is proportional to the wind speed. Some vertical axis wind turbines use pipes or vortex generator towers to turn horizontal airflow into vertical airflow through casings or diffusers to increase speed. Sometimes they also use solar energy or burn some kind of fuel to turn horizontal airflow into vertical airflow. direction of airflow.
6. Runoff twin-wheel effect wind wheel
Runoff twin-wheel effect or twin-wheel effect is a new type of wind energy conversion method.
First of all, it is a double-wheel structure. Compared with the horizontal axial flow fan, it is a radial flow type. Like the existing vertical axis fans, the blades are arranged along the long axis and can be directly used. The single-wheel vertical-axis wind wheel works by rotating due to the thrust of the wind. Because the blades on both sides of the shaft receive wind force at the same time, the torques are opposite and cancel each other out, so the output torque is not large.
Designed as a two-wheel structure and installed close together, running synchronously, the original dependence of the vertical axis torque output on the hydrodynamic shape of the blade is changed to the utilization of the vortex force generated by the rotation between the two wheels. The two wheels borrow force from each other and push each other. ; And the reverse wind flow blowing between the two wheels can block each other, and then distribute it to the outside of the two wheels in turn, so that the outside of the two wheels can get a superimposed wind flow, so that the outer edge linear speed of the two wheels can be high. Depending on the wind speed, the mutual assistance of the two-wheel structure actively utilizes the characteristics of wind power to produce a "two-wheel effect".
Compared with some single-wheel structure wind turbines, external shielding methods, movable pitch changes and other passive designs are used to reduce the impeller rotation reset resistance, which reflects the characteristics of actively utilizing wind power. Therefore, this invention not only has a practical effect and promotes the research and development of wind power utilization, but also has new fluid mechanics significance. It opens up a new space for the development of wind energy and is a basic invention. This two-wheel fan has simple design, easy manufacturing and processing, low rotation speed, lowered center of gravity, good safety, low operating cost and low maintenance. It has obvious characteristics such as ease of use and no noise pollution. It can be widely popularized and promoted to meet China's energy conservation and emission reduction needs, and has great market prospects.