A wind turbine converts wind energy into a rotating movement, which is used by a generator to generate electricity.
The two main types of wind turbine are the horizontal axis turbine and the vertical axis turbine. Horizontal axis wind turbines are the most used worldwide. Vertical axis wind turbines are independent of wind direction. Vertical axis turbines are very suitable for use in urbanized areas or in buildings.
For wind turbines, scheduled maintenance is carried out on average four times a year: visual, lubrication, electrical and mechanical maintenance. This is done as much as possible on days without wind, so that there is the least possible production loss.
Parts of a wind turbine
A wind turbine consists of a base, a mast, a gondola that contains the real turbine and finally wicks.
Wind turbine base
A wind turbine must be well anchored to the ground in which it is located. Sometimes, a shallow base is used for cost reasons. The base is made of concrete and is equipped with penetrations through which the electrical wiring can pass.
In marine wind farms there are three types of usual foundations, a three-legged foot (tripod), a spoon base or a straight mast. The possibility of making floating windmills without direct anchoring to the seabed is being investigated. This would allow wind turbines to be placed in deeper waters and use more renewable energy with smaller investments. However, these are still in the test phase.
Because modern wind turbines are larger than previous versions, (still) it is not possible to use their base for new wind turbines.
The mast of a windmill must be able to withstand many loads. Even greater than the load on the gondola, the generator and the blades is the wind load that the mast has to bear. That is why the rule is: the higher the mast, the wider the foot. The height of the axis of a wind turbine has also increased considerably over the years. While wind turbines were around 15 meters high around 1980, in the mid-1990s they were already 50 meters high. Today, wind turbines average 100 meters high. The expectation is that in the future the wind turbines will have an average shaft height of 150 to 200 meters high.
The mast can be made of concrete or steel. Depending on its size, it can be raised with winches. Larger samples must be assembled with a tap. Inside the mast is a ladder, possibly an elevator and power cables.
The transport of masts from the place of production to the construction site is a great logistical challenge. Because a mast cannot be transported in one piece in terms of weight and size, the mast is transported in parts and assembled on site. The various components are as large as possible. A steel pole consists of two to four sections that are made together with flange connections. The thickness of the wall is 20 to 60 millimeters.
Because the surface of the earth reduces the wind speed by friction, the energy efficiency of wind turbines increases with height. This means that at a higher height more kinetic energy is obtained from the wind to generate more wind energy.
In the gondola of a wind turbine there is a generator and a gearbox in the gondola. The generator converts the kinetic energy of the shaft into electricity and can be compared with a great dynamo. Most wind turbines have a gearbox.
This works like a gearbox: it increases the speed of rotation. The gearbox is a vulnerable component, which means that some manufacturers opt for a direct drive generator, the so-called direct drive or gearless. Wind turbines are equipped with an aerodynamic braking system to be able to stop them during emergency or maintenance situations. A weather vane in the gondola measures the wind direction. As soon as it changes, a handheld engine points the gondola directly to the wind.
Blades of a wind turbine
The blades of a wind turbine are important components. Modern blades are made of fiberglass or carbon fiber reinforced plastic. The maximum length of the blades of modern wind turbines is about 65 meters for land turbines and approximately 85 meters for offshore turbines. The center is the point where the blades meet.
The blades rotate at a constant speed of between 15 and 40 revolutions per minute. However, an increasing number of turbines operates at a variable speed. The revolutions of rotation depend on a physical limit that is the maximum speed of the tips of the blades. This maximum speed is constant with all wind turbine rotors, but what makes the revolutions vary is the length of the blades. An increase in the length of the blades implies an increase in radial speed with the same revolution. This means that wind turbines with a larger rotor diameter (from 90 meters) have a maximum of about 19 turns per minute. Therefore, large wind turbines rotate more slowly than small wind turbines.
Risks of an accident in a wind turbine
Also in wind turbines, accidents sometimes occur. Often, wind turbines are in the open field and not in a densely built environment, so accidents do not usually cause personal injury.
If there is an injury, this is often related to the work done. Because windmills are very tall and extend above existing buildings, fires and destructive rotor blades in windmills give a spectacular view.