How a modern wind power turbine works
The wind turbine converts the wind’s kinetic energy into electricity.
The hub and blades of the wind power unit, or aerogenerator, are called the turbine (or rotor). Behind the turbine in the nacelle (engine house) is the rest of the electrical equipment and machinery (see sketch with cross-section). The nacelle is mounted on a tower in order to allow the wind to flow freely through the turbine, and because the speed of the wind increases considerably with the height above ground.
In the vast majority of wind power turbines the nacelle contains a yawing gear system, which ensures that the turbine automatically faces into the wind. The blades slow the wind down and recover part of its kinetic energy. The turbine on the wind power turbines at Horns Rev 1 (Horns Reef Offshore Wind Park 1) is 80 metres in diameter with a slewing area or sweep of 5,024 sq.m, in other words the size of a football pitch.
The mass of air sweeping through the slewing area every second at a windspeed of 10 m/s amounts to about 70 tonnes. That’s the equivalent of two fully loaded tankers.
The blades are made from composite material glass fibre reinforced plastic, which makes for a durable design. The turbine blades have an integral, lightning protection system, which offers protection from damage caused by strokes of lightning. The weight on the blades is typically more than 10 tonnes. Most towers are manufactured from steel, with a height of 60-100 metres. Their weight varies from 125 to 200 tonnes. However, even larger turbine towers and blades are ”in the pipeline”.
Exploiting the wind
As the wind blows, it creates a pressure difference in front of and behind the blades, causing the blades – and the turbine axle or shaft – to rotate. The turbine axle drives a generator, which generates electricity. The generator is located in the housing on the top of the tower, and the electricity is transmitted to the power grid via cables. The principle of a wind power turbine is remarkably similar to an old-fashioned bicycle dynamo.
The shaft of the turbine is connected to a generator located inside the wind power turbine’s engine house.
Between the turbine and the generator there is normally a gear, which converts the turbine’s low speed of, for example 6-16 revolutions per minute (r.p.m.) to the generator’s 1,500 r.p.m. The generator produces electricity, which is distributed through the national grid.
Wind power and the grid
When there is only a slight or no wind, the wind power turbines are ”on hold”, poised and ready to go. When the wind gets up sufficient speed, approximately 4 m/s, production starts automatically. At 12-14 m/s the wind power turbine produces its full output. In powerful winds, when the windspeed exceeds 25 m/s or so, the aerodynamic stresses are so great that the wind power turbines automatically stop in order not to cause unnecessary wear and tear.
3. Blade bearing
5. Main bearing
6. Main shaft
7. Transmission case
8. Brake disc
10. Service crane
12. Wind gauge (transducer)
14. Crown gear
15. Tower (mast)
16. Machine bed
17. Nacelle (engine house) casing
18. Oil filter
19. Generator fan
20. Oil cooler