The yaw mechanism turns the turbine so that it faces the wind. Sensors are used to monitor wind direction and the tower head is turned to line up with the wind. Towers are mostly tubular and made of steel, generally painted light grey. Lattice towers are used in some locations. Towers range from 25 to 80 meters in height.
Turbines can range in capacity from several kilowatts to several Megawatts.
The crucial parameter is the diameter of the turbine - the longer the blades, the larger the areas swept by the rotor and the greater the energy output. At present the average size of new machines being installed is 600 kilowatts, although there are 1.5 Megawatt machines on the market. The trend is towards larger machines. There are many wind turbine designs, suggesting that there is still plenty of scope for innovation and technological development. Gearless and variable speed machines follow, again with three blades.