Wind energy technology is one of the oldest forms of renewable energy but modern wind turbines and the infrastructure that supports them use the latest materials and skills combined to get the most from their reliability, efficiency and safety.
The wind passes over the blades creating a difference in air pressure (like lift on an aircraft wing) which causes the rotor to turn. The blades turn a low-speed shaft inside the nacelle: gears connect the low speed shaft of the rotor with a high speed shaft that drives a generator. Here, the slow rotation speed of the blades is increased to the high speed needed for the generator.
The rapidly spinning shaft drives the generator to produce electric energy. Electricity from the generator goes to a transformer which converts it to the right voltage for the electricity grid. The electricity is then transmitted via the electricity network.
The towers are mostly tubular and made of steel with concrete foundations underground level. The blades are made of fiberglass and they are light grey because it is inconspicuous under most lighting conditions. The finish is matt, to reduce reflected light.
The average size of onshore turbines being manufactured today is around 2.5-3 MW. One 2.5 MW onshore turbine produces power for over 1,500 average EU households.
Offshore turbines currently reach just over 6 MW with a rotor diameter of 120 metres – longer than a football field and powering around 5,500 average EU households.
Wind turbines start operating at wind speeds of 4 to 5 meters per second and reach maximum power output at around 15 meters/second. At very high wind speeds, i.e. gale force winds, (25 meters/second) wind turbines shut down. A modern wind turbine produces electricity 70-85% of the time, but it generates different outputs depending on the wind speed.
Over the course of a year, it will typically generate about 30% of the theoretical maximum output (higher offshore). This is known as its capacity factor. The capacity factor of conventional power stations is on average 50%. Because of stoppages for maintenance or breakdowns, no power plant generates power for 100% of the time.
Wind turbines can carry on generating electricity for 20-25 years. Over their lifetime they will be running continuously for as much as 120,000 hours. This compares with the design lifetime of a car engine, which is 4,000 to 6,000 hours.