Increasing the Coefficient of Performance of Wind Turbine by Applying Contra Rotating Rotor System

The development of wind power in India began in the 1990s, and has significantly increased in the last few years. Although a relative newcomer to the wind industry compared with Denmark or the US, India has the fifth largest installed wind power capacity in the world. In 2009-10 India's growth rate is highest among the other top four countries. Increasing the Cp [1] value increases the overall efficiency and hence several methods implemented to increase the efficiency one among these is applying contra rotating rotor system of wind turbine.

The theoretical maximum coefficient of performance (Cp) value of blades used in wind turbine is 0.59. In practical case out of 0.59 only 60 to 70% can be achieved .This is done by employing a contra rotating rotor systems. The contra[2] rotating rotors contain two set of rotors, each rotor containing three set of blades. Front set of rotor rotates in clockwise direction and rear set of rotor rotates in the counter clockwise direction.

In contra rotating wind turbine, the second set of rotor will need a lesser energy but it almost produces the torque which is equal to the front set of rotor. So the combination of both the rotors will give the maximum output.

Both the rotors are placed before the tower. The distance between the first and second set of rotor is minimized such away that the lift and drag which produced by the first set of rotor will operate the rear set of rotor.

The modeling is done by using the software Pro/E. The 3D model is transferred to gambit by IGES format. The flow field is analyzed using Fluent 6. The lift, drag and thrust values obtained and are used to compute Cl[3], Cd[4] and Cm[5] and also Cp.