What Is A Wind Turbine?
Wind turbines are devices that are extremely important in the production of sustainable energy due to their ability to produce electricity from the kinetic energy of the wind, but how do a wind turbines work? They are the opposite of a fan, where we use electricity to generate wind.
Wind turbines come in a range of shapes and sizes dependent on space and location and sometimes rotate about a different axis. The largest of wind turbines are easily visible and tend to be installed in large open spaces e.g. fields and at sea. When many wind turbines are installed in proximity, the area is known as a wind farm.
Due to the pledges made by nations around the world towards sustainable development and energy generation, wind turbines are becoming increasingly popular and important. Large numbers of installations led to wind turbines/wind farms generating approximately 650 GW of power as of 2020.
Wind turbines can also be used for smaller components instead of generating electricity for the electrical grid. Small wind turbines are used to charge batteries on vehicles such as boats and caravans.
How Do Wind Turbines Work?
The most well-known wind turbines are the large wind turbines installed out at sea and in large farms and these type of wind turbine work on a simple principle. These types of wind turbine work from the same principle as an aeroplane. An aeroplane wing generates lifts by a pressure difference across the top and underneath the wing.
Air travels quicker over the top of the wing, creating a high-pressure region. Underneath the wing, the air travels slower creating a low-pressure region. The pressure differences generate a force acting upwards.
Large wind turbine blades utilise the same shape like an aeroplane wing. As the wind travels over the turbine blades, pressure regions are created over the surface. The pressure differences result in a force and hence the movement of the blades.
How is Electricity Converted to the Grid?
Wind turbines generates AC electricity, which requires amplifying allowing it to be added to the national grid. For this to be achieved, a transformer is needed. A transformer is used because the voltage produced by wind turbines is not high enough. The transformer increases the voltage making it compatible with the national grid. The voltage is increased to the region of 150 – 800 kV.
How Is Wind Generated?
The wind is generated primarily due to the uneven heating of the earth’s surface. At different temperatures, the air has varying densities. The difference in densities causes the air to circulate – the warm air travels up and the cold air down in a circular motion generating wind.
Other factors affecting wind are the terrain, lakes, oceans, vegetation.
Types of Wind Turbines
There are two primary types of wind turbines – horizontal axis turbines and vertical axis turbines.
Horizontal Axis Wind Turbines
Horizontal axis turbines are a traditional wind turbine that many people are familiar with. They commonly have three blades and are operate upwind. Onshore turbines tend to have concrete foundations to keep them secure and stable while experiencing forces from the wind. Offshore turbines that are well into the ocean, their base is floating. Although the base is floating it has a large enough mass to keep the turbine stable.
Vertical Axis Wind Turbines
Vertical axis turbines come in a variety of forms, however, unlike horizontal axis turbines, they do not need to change direction to face the wind – they are omnidirectional.
What Components Are In Wind Turbines
Blades
The most obvious component of a wind turbine is the blades. Wind turbines tend to have either two or three blades. As discussed above, when wind travels over the blades, a lift force is generated, which rotates the blades.
The blades are commonly made of composites composed of glass and carbon fibre.
Rotor
The blades and hub of the wind turbine together form the rotor, initiating the rotational movement of the wind turbine.
Low-Speed Shaft
The low-speed shaft is connected directly to the rotor. It is called a low-speed shaft due to its low rpm (revolutions per minute) and matches the speed at which the turbine blades are travelling. The speed at which the shaft travels is generally between 30 – 60 rpm.
Gearbox
Most generators require a high rotational rate (1,000 – 1,800 rpm) to be able to generate electricity. 30 – 60 rpm is not high enough, therefore a gearbox is required to create mechanical advantage and generate a high rotational rate. The gearbox is a costly part of the wind turbine, and a way to remove this component would be via the introduction of a direct drive system to generators that can operate at lower speeds.
High-Speed Shaft
The high-speed shaft is the output of the gearbox and rotates anywhere between 1,000 – 1,800 rpm to help drive the generator.
Generator
The high-speed shaft drives the generator, which produces 60 cycle AC electricity.
Anemometer
A key component of a wind turbine is the anemometer, which is a device that is used to measure the speed of the wind flow. The measurement of the wind speed allows the control system to turn the turbine on and off if the wind speed is too high or low.
Controller
Wind turbines can only operate at certain speeds. They can not operate at speeds below 8 mph and above 55 mph. Speeds above 55 mph have the potential to cause harm to the turbines if they operate. It is the role of the controller to turn the wind turbine on or off depending on the wind speeds measured by the anemometer.
Pitch System
It is the pitch systems responsibility to turn the wind turbine to ensure that it is not facing wind speeds that are too high or too low, meaning they cannot produce electricity.
Brake
The brake has the role of stopping the rotor, which is only generally required in the case of an emergency. The brake can be applied mechanically, electrically or hydraulically.
Wind Vane
The wind vanes measures and communicates the direction of the wind to the yaw system.
Yaw System
The yaw system is comprised of the yaw drive and the yaw motor. The yaw drive has the role of ensuring the wind turbine is facing the wind as the direction of the wind can change regularly. The motor is the power behind the yaw drive allowing it to rotate.
Nacelle
The nacelle is the horizontal housing at the top of the turbine. The nacelle houses all the components at the top, such as the gearbox, generator, shafts etc.
Tower
The tower is the central vertical tube of the wind turbine and is made of steel or concrete (normally steel). The tower acts as structural support for the wind turbine because a wind turbine must withstand large forces like the wind speed increases with height. Inside, there is access to the top, via stairs, for any maintenance required on components such as the gearbox etc.
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