Aerodynamic power generators can be classified into vertical generators, including Darrieus or Savonius types, and propeller-equiped horizontal generators. Most generators used today are horizontal types. Horizontal wind force generators come in various capacities, from small to large and vertical types (Darrieus) are widely used in capacities below mid-sized generators. The horizontal generators, with no exceptions, should have th blades facing the winds. To make this possible, manually yaw the body of the wind power generator or use the tail blade so it can spontaneously face the winds. On the other hand, vertical wind power generators have blades revolve around a vertical axis and do not require yawing mechanism as it is unrelated to the direction of winds. The way of controlling the outputs of the generators can be classified into two: with a controller or with the blades. An example of the former is the coil-type induction generator that controls the output by varying it through slip changes in the generator as the wind velocity increases. An example of the latter is the control of output using the aerodynamical characteristics of the blades: concretely classified into stall control and pitch control. Stall control puts a brake on the blades by generating turbulence on the rear of the blades in case of the wind velocity exceeding rated velocity and pitch control controls the torque by altering the blade angle. When the wind velocity increases with the wind turbine generating normal output, alter the pitch angle of the blades or move it to reduce the torque. This is achieved when the angle of attach on the blades is decreased. Eventually, the pitch should be controlled to increase the pitch angle.
1. Horizontal Blade
The angle formed by the revolving surface of the blades on horizontal wind power generators and the chord line of the blades is defined as the pitch angle. Since the blade is twisted as it reaches the root from the tip, the revolving surface and the chord line of the blades unify on the tip during normal drive for 0 pitch angle. The ratio of the chord lengths on the tip and the root of the blades is called the Taper Ratio. .
2. Vertical Blade
When the revolving angle of vertical wind turbine is centered the wind turbine revolves from 0 to 360 when viewed from the top (Wind Turbine). When the blades of the turbine face the winds, that is when the chord lines of the winds and the blades accord, the revolving angle is 0, defining the complete opposite 180. The angle of attach of the blade refer to the angle formed by the chord line of the blade and the direction of the winds. When the blades revolve the driving velocity of the blades combine with the wind velocity in vector science to generate a resulting wind velocity that does not equal the actual wind velocity. The life and the drag impact the blades according this resulting wind velocity. The angle formed by this resulting wind velocity and the chord line of the blades is defined as the angle of attach and its variable is.