5. Offshore Wind

5.3.1. Technology Types (Level 2)

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Operating Principles

The wind turbine operation principle is straightforward. The wind causes the rotors to start rotating the main shaft which is connected to the rotor hub.  Through the gearbox, the rotor shaft motion is transmitted to the generator which produces power.

As mentioned in Level 1, there have been designs of both vertical and horizontal axis turbines used in the past (illustrated above). Vertical wind turbines were abandoned in the mid-1990’s due to aerodynamic inefficiency since the range of the angle of attack between the wind and the rotor blades is very wide.

Horizontal wind turbines can be classified into several categories since many different concepts may be used related to the operation of the turbine. There are upwind turbines with blades facing the wind. Downwind turbines are the opposite as the wind flows from the rear of the turbine towards the rotors.

Wind turbines may also be classified according to the method by which their power is regulated at high wind speeds. One category is stall-regulated wind turbines. These types of turbines have constant rotor blade pitch angle which, as wind speed increases, the blades become increasingly stalled, thus regulating the rotational speed of the rotor. The second category is the pitch regulated wind turbines which, instead of using a fixed rotor angle, alters the angle in order to regulate the power of the wind turbine.

Main components






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