Wind turbines convert the energy of the wind into electricity. There are two basic components to a wind turbine: blades that are moved by the wind and the mechanical gears and electricity generator. As the wind moves the turbine blades, the rotor shaft moves the gears inside the gearbox. This movement creates energy, which is captured by the electricity generator and added to the power grid. There are two types of wind turbines: horizontal axis and vertical axis.
A horizontal axis wind turbine (HAWT) is very similar to a windmill in appearance. The electrical generator and main rotor shaft are located at the top of the tower. Wind sensors and servomotors are often used to automatically align wind turbines with the direction of the prevailing wind. The gearbox converts the large, slow rotation into the rotational speed necessary to generate electricity.
The blades of wind turbines are very stiff and made from a combination of hard plastics and light metals. The blades are installed in front of the tower and are usually pointed upwind. This is done to prevent the blades from being forced back into the tower and to accommodate turbulence forces
There are usually three blades on a wind turbine. They are between 65 to 130 feet (20 to 40 meters) long and lightly colored. In the event of high wind speeds, all wind turbines have a shut down feature. This feature is used to avoid damage to the wind turbine equipment.
A vertical axis wind turbine (VAWT) differs slightly from the HAWT. In this model, the generator and gearbox are located on the ground, at the base of the turbine. This shift allows greater flexibility and removes the need to point the turbine directly into the wind. The location of the mechanical equipment at the bottom of the turbine makes them more accessible for repairs and maintenance.
VAWTs are usually installed on the ground or on a building rooftop. The wind speed at this height is usually slower, and therefore generates less energy. One possible work around is to create a very long axis, which requires significant resources and materials.
Rooftop mounted units pick up wind that has been redirected over the roof by the shape of the building. This feature can significantly increase the wind speed. A rooftop turbine should be installed so that the blades are at least half the building height off the roof. This is the ideal distance to capture the most wind energy.
