Whether they’re large or small, most wind turbines connected to the grid are similar in design and made up of the following components. Wind turbines consist of the blades attached to a hub, which is jointly called the rotor.
The rotor is connected to a the nacelle, and the nacelle holds the key electrical and mechanical equipment at the top of the tower including the main shaft, gearbox and generator.
Here’s an illustration and simple breakdown of all the features that come together to create a wind turbine.
The foundation for wind turbines is constructed from concrete reinforced with steel. The condition of the soil and the strength of the wind will dictate the design aspects of the foundation.
It’s important that the foundation is constructed properly because it has to support the vertical load from the turbine, as well as the horizontal loads from the force of the wind.
There are several designs for the towers of wind turbines:
- Tubular steel
- Combination of these
Smaller wind turbines can also come on wood or guy-wired pole designs. The towers are either delivered in 20-30 meter segments or containers, or in the case of concrete are made directly on-site and bolted to the foundation. The average tower height for a larger wind turbine is about 80 meters or 260 feet.
The aerodynamic shape of wind turbine blades is usually constructed out of composite fiberglass with or without carbon fibers and with or without a support spar inside. The shape of the blades is designed so pressure differences across the surfaces causes them to rotate. And the larger the blades, the more power the wind turbine can ultimately produce.
The blades are connected to the hub, which is then connected to the main shaft, allowing rotation.
The rotor is the assembly of the hub and the three blades together. The average rotor diameter of a larger wind turbine is about 100 meters or more than 320 feet.
Found at the top of the tower, the nacelles house the electrical and mechanical components of the turbine. Some of the electrical components can also be based in the bottom of the tower or in a little house or box next to the wind turbine. At the top of the nacelle there is an anemometer and wind vane to monitor wind conditions (speed and direction).
Main Shafts and Gearboxes
The main shaft is a drive shaft that is connected to the rotor on the one side and the gearbox (in turbines that have a gear box) or to the generator (direct drive, without gearbox) and it’s called the low-speed shaft.
In the case of a geared wind turbine, there is a second shaft which connects the gearbox with the generator, which is called a high speed shaft.
Most generators are connected to the grid, depending on the size and application of the turbine. The electricity from the generator is transformed by the inverter, converter and transformer to make it suitable for the grid. The controls system known as SCADA, controls the wind turbine functions and the electrical quality to the grid to ensure safe connection.
Pitch Control Systems
The pitch system turns the angle of the blades in and out of the wind to speed up or slow down rotational speed. The pitch control system will angle the blades out of the wind in heavy wind conditions to protect the equipment from over-speed.
The Pitch system is either hydraulic or electric. A number of smaller or older wind turbines do not have a pitch system and rely on the aerodynamical properties of the blades (called stall effect) to achieve the same function.
The yaw system connects the nacelle to the tower and turns the nacelle with the blades horizontally into the wind to ensure that the turbine is capturing the maximum energy out of the wind. Based on the information from the wind vane on top of the nacelle, a controller tells the wind turbine where the wind is coming from and changes the direction of the turbine.
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