Basic Construction of Wind Turbine

Major Parts of Wind Turbine

Tower of Wind Turbine

The tower supports every other part of a wind turbine. It raises the rotor high enough that the blade tips stay clear of the ground during rotation, and it must be tall enough to reach the stronger winds that blow higher above the ground. The required height ultimately depends on the power capacity of the turbine. Towers in commercial wind power plants usually stand between 40 and 100 meters, and many modern utility-scale towers are taller still; the average U.S. land-based hub height reached about 103 meters in 2023. These towers may be either tubular steel towers, lattice towers or concrete towers. Large wind turbines normally use a tubular steel tower, manufactured in sections of 30 to 40 meters in length.Each section has flanged ends with bolt holes, and the sections are bolted together at the site to form the complete tower. The tower has a slight conical shape, which gives it better mechanical stability. A lattice tower is assembled from steel members such as GI angles or tubes, bolted or welded together to form a complete tower of the desired height. These towers cost much less than tubular steel towers but look far less pleasing. Transportation, assembly and maintenance are straightforward, yet modern wind power plants avoid lattice towers because of their appearance. Another type of tower used for small wind turbines is the guyed pole tower: a single vertical pole held upright by guy wires anchored on several sides. The many guy wires make the footing area difficult to access, so this type of tower is avoided on agricultural land.

A hybrid tower is another option for small plants. It is also guyed, but instead of a single central pole it uses a thin, tall lattice mast, so the design combines a lattice tower with a guyed tower.

Nacelle of Wind Turbine

The nacelle is a large housing on top of the tower that contains the main wind turbine components: 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 because they convert wind energy into mechanical energy. Shaped like airplane wings, they generate aerodynamic lift as the wind flows over them, and that lift turns the rotor and its shaft. Onshore blades are typically 40 to 90 meters long, while offshore blades can exceed 100 meters. A blade must be strong enough to withstand storms yet light enough for smooth rotation, so manufacturers build them from fiberglass and carbon fiber.

A modern turbine normally carries three identical blades bolted to a central hub, each set 120^o apart. This arrangement distributes the mass evenly around the hub and keeps rotation smooth.

Shaft of Wind Turbine

The shaft coupled directly to the hub is the low-speed shaft, and it spins at the same rpm as the rotating hub. With a low-speed generator, this shaft drives the generator directly. In most turbines, however, a gearbox couples the low-speed main shaft to a high-speed shaft, so the mechanical energy delivered by the blades reaches the generator at its required speed.

Gearbox

A wind turbine rotor turns slowly, yet most electrical generators need high-speed rotation to produce electricity at the desired voltage level. The gearbox provides that speed multiplication. For example, if the gearbox ratio is 1:80 and the low-speed main shaft turns at 15 rpm, the gearbox raises the generator shaft speed to 15 × 80 = 1200 rpm.

Generator

The generator converts mechanical energy from the shaft into electrical energy. Modern wind turbines typically use induction generators, often in doubly-fed form, whose converters allow the shaft speed to vary with the wind while the output stays locked to the grid frequency. Some wind turbines use Permanent Magnet DC generators or synchronous generators with full power converters, which take additional steps to stabilize the output.

An induction generator whose stator connects directly to the grid delivers power at the grid frequency across its small operating slip range, and doubly-fed designs add a rotor converter that permits roughly ±30 percent speed variation around synchronous speed. If we use a three-phase synchronous generator, we first rectify its output to DC and then convert it to AC of the desired voltage and frequency using an inverter circuit, because the alternating power produced by the synchronous generator varies in voltage and frequency with the speed of the rotor. For the same reason, some cases use a DC generator, whose DC output is inverted to AC of the desired voltage and frequency before being fed to the grid.

Power Converter

Wind speed is never constant, so the electrical output of the generator also varies, but the grid needs stable voltage. A power converter is an electrical device that conditions the generator output and stabilizes the alternating voltage transferred to the grid.

Turbine Controller

The turbine controller is a computer (PLC) that manages the entire turbine. It starts and stops the turbine and runs self-diagnostics in case of any error in the turbine.

Anemometer

It measures the wind speed and passes that information to the PLC, which uses it to control the turbine power.

Wind Vane

It senses the direction of the wind and passes the direction to the PLC. The PLC then turns the nacelle so that the blades face into the wind and cut the maximum airflow.

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

The blades and other components of a wind turbine are housed in the nacelle. Whenever the wind direction changes, the nacelle must face into the wind to extract the maximum energy from it. For this purpose, the yaw drive motor rotates the nacelle, controlled by the PLC using the wind vane information to sense the wind direction.