- Wind Turbine Definition: A wind turbine is a machine that converts wind energy into electrical energy through mechanical parts like blades, a shaft, and a generator.
- Tower Types: Towers can be tubular steel, lattice, concrete, or guyed pole, providing support and optimal height for the turbine.
- Nacelle Components: The nacelle houses the generator, power converter, gearbox, and controller, crucial for energy conversion and system control.
- Rotor Blades Function: Blades capture wind energy and turn it into mechanical energy, rotating to drive the shaft.
- Construction of Wind Turbine: The construction includes towers, nacelles, blades, shafts, gearboxes, and generators, each part playing a key role in producing electricity.
Major Parts of Wind Turbine
Tower of Wind Turbine
Tower is very crucial part of wind turbine that supports all the other parts. It not only supports the turbine but raises the turbine to sufficient height so that its blades tips would be at safe height during rotation. Not only that, we have to maintain the height of the tower, so that it can get sufficiently strong wind. The height of tower ultimately depends on the power capacity of wind turbines. The tower of the turbines in commercial wind power plants usually ranges from 40 meters to 100 meters. These towers may be either tubular steel towers, lattice towers, or concrete towers. We use a tubular steel tower for a large wind turbine. These are normally manufactured in a section of 30 to 40 meters in length.
Each section has flanges with holes. Such sections are fitted together by nut bolts at the site to form a complete tower. The complete tower is slight conical shape to provide better mechanical stability. We assemble a lattice tower by different members of steel or GI angles or tubes. All members are bolted or welded together to form a complete tower of desired height. The cost of these towers are much less than that of steel tubular tower, but it aesthetically looks not as good as steel tubular tower. Although, transportation, assembling, and maintenance are quite easy but still use of lattice tower is avoided in modern wind turbine plant due to its aesthetic look. There is another type of tower used for small wind turbines, and this is guyed pole tower. Guyed pole tower is a single vertical pole supported by guy wired from different sides. Because of numbers of guy wires, it is difficult to access the footing area of the tower. Because of that, we avoid this type of tower in the agricultural field.
There is another type of wind turbine tower used for small plant, and this is a hybrid type tower. Hybrid type tower is also a guyed type tower, but the only difference is that instead of using a single pole in the middle it uses a thin and tall lattice type tower. Hybrid type tower is hybrid of both lattice type and guyed type tower.
Nacelle of Wind Turbine
The nacelle is a large box on top of the tower that contains key wind turbine components. Inside, it holds the electrical generator, power converter, gearbox, turbine controller, cables, and yaw drive.
Rotor Blades of Wind Turbine
Blades are the main mechanical parts of a wind turbine, converting wind energy into mechanical energy. Designed like airplane wings, they rotate when struck by wind, transferring energy to the shaft. Blades can be 40 to 90 meters long and must be strong enough to withstand storms but light enough for smooth rotation. They are made of fiberglass and carbon fiber.
In a modern turbine, normally three identical blades are fitted to a central hub using nut bolts. Each identical blades are aligned at 120o to each other. The process makes a better distribution of mass and gives the system more smooth rotation.
Shaft of Wind Turbine
The shaft directly connected to the hub is a low-speed shaft. When the blades rotate, this shaft spins with the same rpm as the rotating hub. We couple this shaft directly to the electrical generator in case of a low-speed generator. But in most cases, the low-speed main shaft is geared with a high-speed shaft through a gearbox. In this way, the rotor blades transfer its mechanical energy to the shaft which ultimately enters into an electrical generator.
Gearbox
The wind turbine does not rotate at high speed rather it rotates gently at low speed. But most of the electrical generators require high-speed rotation, to generate electricity at a desired voltage level. So there must be some speed multiplication arrangement to achieve the high speed of the generator shaft. The gearbox of the wind turbine does this. Gearbox increases the speed to much higher value. For example, if the gearbox ratio is 1:80 and if the rpm of a low-speed main shaft is 15, the gearbox will increase the speed of generator shaft to 15 × 80 = 1200 rpm.
Generator
The generator converts mechanical energy from the shaft into electrical energy. Modern wind turbines typically use induction generators, which can handle variable shaft speeds caused by changing wind speeds. This helps maintain consistent frequency and voltage in the generated power. Some wind turbines use Permanent Magnet DC generators or synchronous generators, which require additional steps to stabilize the output.
Because the induction generator always produces electric power synchronized to the connected grid irrespective of the speed of the rotor. If we use the three-phase synchronous generator, then we first rectify the output power to DC and then convert it to AC of desired voltage and frequency using inverter circuit. Because the alternating power generated by the synchronous generator is not constant in voltage and frequency, rather it varies with speed of the rotor. Because, for the same reason, in some cases, we use a DC generator for the purpose. In these cases, the output DC power from generator inverted to AC of desired voltage and frequency, before feeding it to the grid.
Power Converter
Because wind is not always constant, so electrical potential generated from a generator is not constant, but we need a very stable voltage to feed the grid. A power converter is an electrical device that stabilizes the alternating output voltage transferred to the grid.
Turbine Controller
Turbine controller is a computer (PLC) that controls the entire turbine. It starts and stops the turbine and runs self diagnostic in case of any error in the turbine.
Anemometer
It measures the wind speed and passes the speed information to PLC to control the turbine power.
Wind Vane
It senses the direction of the wind and passes the direction to PLC then PLC faces the blades in such a way that it cuts the maximum wind.
Pitch Drive
Pitch drive motors adjust the blade angles to capture maximum wind energy as wind conditions change. This process is called pitching.
Yaw Drive
Blades and other components in wind turbine are housed in a nacelle, whenever any change in wind direction is there, the nacelle has to face in the direction of the wind to extract the maximum energy from wind. For this purpose yaw drive, a motor is used to rotate the nacelle. It is controlled by PLC that uses the wind vane information to sense the wind direction.
