The vast majority of land-based utility-scale wind turbines currently installed in the US range from 1MW to 3MW. These turbines feature rotors with diameters ranging in width from 57 meters out to 114 meters and are perched on top of towers that might vary in height anywhere between 65 meters to 120 meters. The estimated number of wind turbines installed in the US is over 40,000 with installation rates continuing to increase.
What Types of Wind Turbines Are There?
There are two different groups of wind turbines: horizontal axis turbines and vertical axis turbines. The horizontal axis wind turbines are the type that we are most used to seeing in commercial scale wind farms, they are the turbines that look like windmills. Vertical axis wind turbines are more reminiscent of an egg beater and for the most part operate at a lower capacity.
There are many wind turbine manufacturers supplying geared system turbines to the wind industry including Gamesa, Clipper, GE and Vestas. Some manufacturers also provide direct drive systems such as Enercon, M-Torres and Northern Power Systems.
As well as the materials need to construct the rotor blades of the turbines there are turbine towers, footings, foundations and small parts required for every single installation. Each turbine consists of more than 8,000 components. Rather than examine every small piece we are going to take a look at the major components of a wind turbine.
What Are the Components of a Wind Turbine?
Displayed below is an illustration of the major components of a standard wind turbine. To get a better look you can click the image for a larger view.
When looking at a utility-scale wind turbine the rotor consists of three turbine blades, a hub and a spinner. The blades are constructed to a variety of lengths and will be used on a particular wind turbine depending on the prevailing wind conditions for the area. They are made from high-tech materials such as carbon fiber and fibreglass and have high strength-to-weight ratios. The shape of the blades are molded into airfoils to generate lift and this causes the rotor to turn.
The hub section of the rotor is a heavier component and is usually made of ductile cast iron. The hub must be rigid but capable of absorbing a lot of vibration. Around the hub is usually a covering known as a nose cone. This nose cone is also made of lighter materials and is used for two purposes, the first is to protect the hub and the second is for the aesthetic value it gives the turbine.
The nacelle is the outer body of the turbine that contains and protects the majority of the small components of the turbine. The nacelle is connected to the rotor and is made of a material such as fibreglass to ensure protection from the elements. It is attached to the main frame of the turbine and surrounds the working parts that make up the turbine engine.
When the turbine blades catch the wind they begin to turn the rotor and this drives the large shaft that turns the gears in the gearbox. The large shaft and gearbox work together with a generator to generate electricity and this sequence of components are known as the drive train.
One of the features that is necessary for all efficient wind turbines is the yaw drive which is required to keep the rotor facing properly into the wind. The yaw drive is essentially an electric or hydraulic motor and it is mounted on the nacelle where it drives a pinion mounted on a vertical shaft. Another job performed by the yaw drive is to apply a brake when it is necessary to stop a turbine from turning.
During the regular operation of a wind farm it is necessary to be able to control the operation of the turbines. This control is performed by an automated system of sensors that is able to track the speed and direction of the wind as well as the power generation that is being carried out. The blade’s pitch angle, vibration levels and lubrication factors are also measured to determine what changes need to be made to increase the turbine’s efficiency. This system also protects the turbines against dangerous operating conditions and makes changes accordingly.
All land-based wind turbines are connected to the ground by towers. These towers provide a stable base to hold the turbine properly in place and also increases the height of the turbine blades to take full advantage of the wind. It is most common for a turbine tower to measure around 80-100 meters tall.
The entire wind turbine sits atop a solid base to keep it stable and solid. The base is made from poured concrete and reinforced by steel bars. There are commonly two ways in which the base is created. It is either a flat disk that sits around 40 feet in diameter and is around 3 feet thick or it is smaller and deeper at around 15 feet in diameter but 16 feet deep. There are obviously many other way in which the base of a wind turbine may be constructed. This is particularly true of off-shore wind projects where the base has to be a far more carefully thought out design.
There is one other category of wind power generation that is in the early developmental stages that use types of wind turbines and that is the high altitude wind power sector. Although the end result is the creation of wind energy the components of these devices will differ either slightly or drastically from the wind turbines that have been described on this page.