Today, ordinary people know that the windmills with their large, constantly rotating blades are actually wind turbines, but do we understand their internal structure?
A wind turbine is an electrical device that converts wind energy into mechanical work, which drives a rotor to rotate and ultimately outputs alternating current (AC). A wind turbine typically consists of components such as a wind turbine rotor, generator (including the generator itself), directional control unit (tail fin), tower, speed limiting safety mechanism, and energy storage device.
The working principle of a wind turbine is relatively simple. The wind turbine rotates under the action of wind, converting the kinetic energy of the wind into the mechanical energy of the turbine shaft. The generator then rotates under the drive of the turbine shaft to generate electricity. Broadly speaking, wind energy is also solar energy, so a wind turbine can also be described as a thermal energy generator that uses the sun as a heat source and the atmosphere as a working medium.
Wind turbine structure:
(Structure diagram of wind turbine)
Nacelle: The nacelle houses the key equipment of the wind turbine, including the gearbox and generator. Maintenance personnel can access the nacelle through the wind turbine tower. The wind turbine rotor, consisting of the blades and shaft, is located at the left end of the nacelle.
Rotor blades: They capture the wind and transmit the wind power to the rotor shaft. On a modern 600-kilowatt wind turbine, each rotor blade measures approximately 20 meters in length and is designed much like an airplane wing.
Shaft: The rotor shaft is attached to the low-speed shaft of the wind turbine.
Low-speed shaft: The low-speed shaft of a wind turbine connects the rotor shaft to the gearbox. In modern 600 kW wind turbines, the rotor speed is quite slow, approximately 19 to 30 revolutions per minute. The shaft contains conduits for the hydraulic system, which activates the aerodynamic brakes.
Gearbox: The low-speed shaft is located on the left side of the gearbox, which can increase the speed of the high-speed shaft to 50 times that of the low-speed shaft.
High-speed shaft and its mechanical brake: The high-speed shaft operates at 1500 revolutions per minute and drives the generator. It is equipped with an emergency mechanical brake for use in case the aerodynamic brake fails or the wind turbine is under maintenance.
Generator: Commonly referred to as an induction motor or asynchronous generator. In modern wind turbines, the maximum power output is typically between 500 and 1500 kilowatts.
Yaw mechanism: An electric motor rotates the nacelle to align the rotor with the wind. The yaw mechanism is operated by an electronic controller, which senses wind direction via a wind vane. Typically, the wind turbine yaws only a few degrees at a time as the wind changes direction.
Electronic controller: Contains a computer that continuously monitors the status of the wind turbine and controls the yaw mechanism. To prevent any malfunction (i.e., overheating of the gearbox or generator), the controller can automatically stop the wind turbine from rotating and call the wind turbine operator via telephone modem.
Hydraulic system: Used to reset the aerodynamic brake of the wind turbine.
Cooling components: This includes a fan for cooling the generator. Additionally, it includes an oil cooling element for cooling the oil inside the gearbox. Some wind turbines have water-cooled generators.
Tower: The wind turbine tower houses the nacelle and rotor. Taller towers are generally advantageous because higher elevations result in higher wind speeds. Modern 600 kW wind turbines typically have towers ranging from 40 to 60 meters in height. They can be tubular or lattice-shaped. Tubular towers offer greater safety for maintenance personnel, as they can access the top via internal ladders. Lattice towers are more affordable.
Anemometers and wind vanes: used to measure wind speed and direction.
Tail rudder: Commonly found in small wind turbines (generally 10KW and below) with a horizontal axis facing the wind. Located behind the rotating body and connected to it. Its main functions are: 1) to adjust the turbine's direction of rotation, ensuring the turbine faces the wind; and 2) to deflect the turbine's nose away from the wind direction in strong winds, thereby reducing speed and protecting the turbine.
Generator type
Based on the characteristics of fixed-pitch stall type wind turbines and variable-speed constant-frequency variable-pitch type wind turbines, the motors currently installed in China are generally divided into two categories:
1. Asynchronous
(1) Squirrel-cage induction generator; power ratings are 600/125kW, 750kW, 800kW, and 12500kW.
The stator supplies 50Hz alternating current of varying power to the power grid;
(2) Wound-rotor doubly-fed asynchronous generator; power of 1500kW
The stator supplies 50Hz AC power to the power grid, while the rotor, controlled by a frequency converter, indirectly supplies active or reactive power to the power grid.
2. Synchronous type
(1) Permanent magnet synchronous generator; power of 750kW, 1200kW, 1500kW. The magnetic field is generated by permanent magnets, and the stator output is rectified and inverted at full power to supply 50Hz AC power to the grid.
(2) Electrically excited synchronous generator; the magnetic field is generated by the DC current connected to the rotor, and the stator output is rectified and inverted at full power to supply 50Hz AC power to the grid.
Based on the different blade designs, existing wind turbines can be divided into the following two categories:
1. Horizontal axis wind turbine
The most widely used form in the world, with a maximum power of around 5MW.
2. Vertical axis wind turbine
Invented almost simultaneously in China, Japan, and Europe in the early 21st century, this new type of wind turbine differs from the earliest vertical-axis wind turbines (Darrieus type). It boasts higher efficiency than horizontal-axis wind turbines, operates without noise or a steering mechanism, and is easy to maintain. It has become the preferred choice for small and medium-sized wind turbines in the European and American markets. Currently, its power output ranges from 1 kilowatt to 50 kilowatts.
1kW Vertical Axis Wind Turbine
