How a wind turbine works depends on the type of wind turbine discussed.
While most people think of windmills as being the only true type of wind turbine, this is simply not the case, as there are horizontal axis, vertical axis, and various other types of "special" wind turbines in service around the world.
Horizontal Axis Wind Turbines
Horizontal axis wind turbines, also known as HAWTs are the most common and most well known types of wind turbines. They are all modeled after the classic Dutch windmills of yesteryear, but they are considerably more efficient and are able to produce relatively large amounts of energy in comparison to other types of renewable energy. HAWT type turbines have a horizontal rotor shaft and an electrical generator which are both located at the top of a tower. These types of turbines must always be pointed in the direction of the wind if they are to be used efficiently. Older and smaller wind turbines of the horizontal type can change directions via a simple wind vane while large and more modern turbines have special motors in them which allow them to change direction as the wind shifts.
In order to generate power via a HAWT system, the wind must first blow on the giant blades of the turbine. As the wind blows the blades, they begin to rotate in a given direction, based on the angle of deflection of the blades. The rotating blades are connected to a gearbox located at the top of the turbine's tower. In the gearbox, the slow movement of the blades is transformed into a quicker rotation of gears which is much better suited to generating electrical power.
Vertical Axis Wind Turbines
In contrast to horizontal axis wind turbines, there are also vertical axis wind turbines, known as VAWTs, which work in a much different way and are designed to harvest different types of wind. While they are not as well recognized as their horizontal brethren, they do serve an important purpose nonetheless. VAWTS are designed with a vertical rotor shaft, a generator and gearbox which are placed at the bottom of the turbine, and a uniquely shaped rotor blade that is designed to harvest the power of the wind no matter which direction is it blowing.
Types of VAWT Turbines
The first is the Darrieus wind turbine, which is designed to look like a modified egg beater. These turbines have very good efficiency, but poor reliability due to the massive amount of torque which they exert on the frame. Furthermore, they also require a small generator to get them started.
Another type of VAWT is the Giromill. This wind turbine has vertical blades and is essentially a modified Darrieus type turbine. Unlike their predecessors, they have self starting capabilities and do not produce as much strain on the frame, leading to better reliability.
Some of the most advanced vertical axis wind turbines are the Windstar Turbines designed by Wind Harvest. They consist of a variety of aluminum blades which are attached to a centrally rotating shaft. Each rotor has its own generator and if the turbines are located close enough to each other, the center rotor can obtain an efficiency that is on par with the more modern HAWTs due to what is known as the vortex effect.