Wind energy turbines are such wind power processing units that can harness wind resources to produce electricity. Since the latter make use of the latest and the most up to date techniques, these turbines are becoming more popular with the passage of time. Wind energy turbines are, in general, divided into two types – the horizontal axis variety and the vertical axis variety. As these names suggest, this division is based on how the axes of the turbines are oriented. Thus, horizontal axis energy turbines, that are extensively used these days, rotate around horizontally placed axes.

Ideal for the generation of electric power, these turbines have a rotor, which has two or three rotating blades. The latter points in the same direction as that of the wind flow. The rotor, along with these blades, is then attached to a movable shaft, and the latter is connected to an electronic generator. The shafts move, thereby spinning the generator, which, in turn, generates electrical power (from the mechanical energy obtained). Hence, much more important in determining the output efficiency of these turbines is the velocity of wind flow, with the speed of rotation of the propelling blades having much less of an impact.

More upgraded wind turbines generally are also equipped with a gearbox that can add considerable speed to the rotation rate of the blades. Hence, most wind turbines have a downwind orientation from the wind tower. The blades of these wind turbines have a slight upward tilt, so that there are no risks of these blades being forced inside the wind tower, under the effect of strong winds. The extremely stiff nature of the blades is also meant to achieve the same purpose. Wind turbines that point downwind of the wind tower are also produced.

Their blades need not match the direction in which wind blows either. However, these turbines have little resistance power to strong winds, due to frequent fatigue failures, which also render them less efficient. Broadly speaking there are three types of horizontal axis wind turbines – the modern ones, the ones made in the 19th century and those from the 12th century.