Publication

Abstract : Performance analysis of a VAWT and HAWT is highly complex due to fluid structure interactions and blade vortex interactions. However, there are simplified methods such as momentum theory to most expensive CFD models available for performance prediction. CACTUS is neither as simple as the momentum theory nor as complex as the CFD models, it is an open source code that uses the free vortex method to predict the performance of a wind turbine. In this paper, the effect of solidity and wind shear on the performance of an H-type Darrius VAWT is studied using CACTUS. Variation of solidity was achieved by changing the chord length (c/R =0.04-0.07) and number of blades (N =2,3). It has been observed that at lower tip speed ratio (TSR lt; 3) the turbine with longer c/R was found to be more efficient due to large wind interception by the blades; and at higher TSR ( gt; 3) shorter c/R was more efficient due to relatively low wake blade interaction. The improvement in performance due increasing the number of blades is effective only up to a particular TSR. Effect of wind shear due to the tower height from the ground using the power law equation with values of power law coefficient ranging from 0.1 to 0.3 has also been studied. It is observed that the power coefficients of the VAWT under a turbulent boundary layer are in congruence with the experimental results.