The propeller is generally made up of three blades shaped like the wings of an airplane. They measure between 35 and 60 metres in length. They begin to rotate under the effect of a wind speed of under 10 kilometres per hour.
The nacelle rotates automatically so that it is always facing the wind.Optimal wind speed is about 50kph. Beyond 90kph the propellers stop spinning for safety reasons.The spinning propeller turns a low-speed shaft inside the nacelle.
The rotation speed of the shaft is not high enough to produce electricity. However, a gearbox increases the speed to 1500 revolutions a minute and transfers it to a second shaft, connected to a generator.
The generator transforms the kinetic energy into electricity.
Inside the tower, a transformer raises the voltage to 20,000 volts. Electricity is sent by underground or undersea cable to a sub-station, where the voltage is increased again so that it can be injected into the power grid.
Wind farms are clean and sustainable and can be built quickly. However they have their drawbacks. Wind energy is intermittent, depending on the weather and environment. Wind turbines are noisy, don’t always fit happily into the landscape and represent a danger for birds.