Cognitive Classroom - Wind Power
1、 What is wind energy?
Wind energy is the kinetic energy generated by the flow of air. The size of wind energy depends on wind speed and air density. Wind energy is converted from solar radiation, accounting for approximately 1% -2% of the total energy provided by the sun. A portion of it is converted into bioenergy by plants on Earth. The total amount of converted wind energy is 50-100 times that of biomass energy!
2、 Why is wind energy a green energy source?
Wind energy will not have the same environmental pollution problems as conventional energy and nuclear power. On average, installing a 1 megawatt wind turbine can reduce emissions by 2000 tons of carbon dioxide, 10 tons of sulfur dioxide, and 6 tons of nitrogen dioxide per year. Wind power technology is becoming increasingly mature, its economy is improving, and its cost is close to coal-fired power, lower than oil and nuclear power; The construction period of wind farms is short, the construction is flexible, and they can be built in remote areas and coastal islands with inconvenient transportation.
3、 The History of Human Utilization of Wind Energy
China is one of the earliest countries in the world to utilize wind energy. In decades BC, the Chinese people used wind power to grind rice, lift water, grind flour, and use sails to propel ships forward; Abroad, in the 2nd century BC, the ancient Persians used vertical axis windmills to grind rice. The Mis people used vertical axis windmills to grind rice; In the 10th century, Islamic people used windmills to lift water, and in the 11th century, windmills were widely used in the Middle East; In the 13th century, windmills were introduced to Europe; In the 14th century, it became an indispensable driving force in Europe; In the 18th century, wind turbines were used for irrigation and power generation in North America. Since 1920, people have been using wind turbines for large-scale power generation.
4、 China's wind energy resources
China has abundant wind resources, with a total of approximately 700 million to 120 million kilowatts on land and at sea. Mainly distributed in coastal and island areas with abundant wind energy: Shandong, Jiangsu, Zhejiang, Fujian, etc; Wind energy belt in the northern region: three eastern provinces, Hebei, Ningxia, Inner Mongolia, Gansu; The characteristics of wind energy in China include: (1) complementary seasonal distribution of energy resources and hydropower resources; (2) The geographical distribution of wind resources does not match the geographical distribution of power loads.
5、 Composition and principle of fans
A wind turbine is composed of wind turbine, transmission system, yaw system, hydraulic system, braking system, generator, control and safety system, engine room, tower, and foundation.
(1) Blades: Blades are units that absorb wind energy, used to convert the kinetic energy of air into mechanical energy for impeller rotation.
(2) Variable pitch system: The variable pitch system changes the pitch angle of the blades to enable them to be in the optimal state of absorbing wind energy at different wind speeds. When the wind speed exceeds the cut out wind speed, the blades are braked along the pitch.
(3) Gearbox: Gearbox transfers the power generated by the wind turbine under the action of wind to the generator, and causes it to obtain the corresponding speed.
(4) Generator: A generator is a component that converts the mechanical kinetic energy generated by the rotation of the impeller into electrical energy. The rotor is connected to the frequency converter and can provide adjustable frequency voltage to the rotor circuit. The output speed can be adjusted within the range of synchronous speed ± 30%.
(5) Yaw system: The yaw system adopts an active wind gear drive form, which is coordinated with the control system to keep the impeller in a windward state, fully utilizing wind energy and improving power generation efficiency. Simultaneously provide necessary locking torque to ensure safe operation of the unit.
(6) Hub system: The function of the hub is to fix the blades together and withstand various loads transmitted on the blades, which are then transmitted to the generator shaft. The wheel hub structure is fitted together with three radial flares.
Simply put, the working principle of a wind turbine is to drive the impeller to rotate through the wind, and then increase the speed of the generator through the transmission system to drive the generator to generate electricity, effectively converting wind energy into electrical energy.
6、 Classification of fans
(1) According to capacity, wind turbines can be divided into small, medium, and large ones.
(2) According to the speed of the wind turbine, it can be divided into fixed speed and variable speed wind turbines.
(3) According to the blade angle, wind turbines can be divided into stall type and variable pitch type. Variable pitch wind turbines are further divided into electric variable pitch wind turbines and hydraulic variable pitch wind turbines.
(4) According to the number of blades, wind turbines can be divided into single blade, double blade, and triple blade types.
(5) According to the transmission mechanism, wind turbines can be divided into gearbox acceleration type and direct drive type.
(6) According to the type of generator, it can be divided into asynchronous and synchronous wind turbines.
(7) According to the grid connection method, wind turbines can be divided into grid connected and off grid types.
(8) According to the relative position between the main axis and the ground, wind turbines can be divided into horizontal axis and five straight axis wind turbines. Horizontal axis wind turbines can be divided into upwind and downwind wind wind turbines depending on the relative position of the wind turbine and tower.
(9) According to the environment, wind turbines can be divided into high prototype and plain type; Room temperature and low-temperature wind turbines; Conventional and corrosion-resistant wind turbines.
