Design and Experimental Analysis of Oscillating Pitch Bi-rotor Horizontal Axis Wind Turbine

Abstract

Horizontal axis wind turbine (HAWT) is the promising source of machine to harness the wind that flows in a single direction. However, the pitch angle should continuously vary to optimize the energy conversion in the machine. It requires complicate servo mechanism to change the pitch angle as per the direction of the wind. In order to fix the above-mentioned issue, an effort is made to come up with the new design of oscillating pitch bi-rotor small wind turbine. In this work, the concept of oscillating pitch angle is tried. In this pitch angle of the HAWT is oscillate and adjust itself with reference to the direction and the wind speed and does not require any feedback mechanism to control the pitch. In the bi-rotor design, the 3 blade rotor is fixed at both ends of the shaft with a phase shift of 60°; between these two rotors and generator is kept in between the two rotors. So maximum possible effective surface area of the blade will increase which in turn develop more torque than a regular turbine. In this work, the effect of the power coefficient of the new oscillating pitch is compared with the variable and fixed pitch HAWT for different wind velocity. The results of the experiments show that the considerable improvement in the power coefficient of Small Horizontal Axis Wind Turbine with an oscillating pitch and bi-rotor configuration. It is witnessed from the results that the maximum coefficient of power of oscillation pitch bi-rotor turbine is 1.15 times more than that of the fixed pitch turbine. Moreover, it doesn't require any pitch control to reduce the speed of the turbine during unexpected high wind velocity.