Wind turbines convert wind into electricity. They are often situated in groups, or wind farms, either on- or offshore. A large wind farm may consist of hundreds of individual wind turbines, interconnected by a transmission system.
Offshore wind turbines are connected through an internal grid (see Interconnectors ) to an offshore substation, where the voltage is increased to improve transmission over long distances. From the offshore substation electricity is transmitted onshore through a control centre and then to the grid.
Wind drives the turbine’s blades and hub, which make up the rotor. The turbine’s shaft is connected to a generator located in the upper part of the tower. A gearbox, normally situated between the rotor and generator, steps up the slow speed of the rotor to a speed that suits the generator.
An automatic system keeps the turbine pointed into the wind. This allows the utilisation of wind blowing from different directions. Turbine blades are normally made from extremely durable fibreglass-reinforced plastic and sometimes of carbon-reinforced fibres. Lightning protection is built into the blades.
Needs wind of at least 3 Bft
When there is light or no wind, turbines rest in standby mode. When wind blows to a sufficient degree, approximately 4 m/s, the turbine starts operating automatically. It operates at full power when winds are around 6 Bft. In strong winds (in excess of around 10 Bft) the turbine is shut off to prevent unnecessary wear and tear.
In order for a wind farm to be profitable, it must have a good wind position. After an area has been identified, a thorough examination is made of the geographical surroundings, existing roads, electricity grids, proximity to residences, flora and fauna and any restricted areas. Winning the acceptance of nearby residents can sometimes be a major challenge.