Performance Analysis of a Horizontal Axis Wind Lens Wind Turbine

Abstract

In reaction turbines, the main purpose of draft turbine is to increase the available net head and to increase the efficiency. By using the same principle in the case of a wind turbine, we can significantly improve the performance. As we all know that, the power generated by a wind turbine is always directly proportional to the cube of wind velocity at the inlet. If we try to increase inlet velocity by capturing and concentrating locally, there is a significant increase in the output power of a wind turbine. This is to be done by using wind lens technology, which comprises of inlet shroud, diffuser and brim. According to Betz limit, the maximum possible limit of efficiency for any horizontal axis wind turbine is 59.3% [1–3]. But, recent studies had shown that the maximum power coefficient from horizontal axis wind turbine (HAWT) using wind lens technology can be increased beyond the Betz limit. This study compares the maximum efficiency possible from a horizontal axis wind turbine without diffuser and that with diffuser enclosed around a turbine. A numerical simulation is done for the same model using ANSYS CFX with different inlet conditions. The geometry of the diffuser is optimized for the maximum possible efficiency. From this study it is found that a diffuser of divergence angle 8° around wind turbine operated at an optimum wind velocity of 2 m/s (for the chosen wind turbine model) gives the power coefficient of 0.6 which is greater than Betz limit.