Two-stage optimization of three and four straight-bladed vertical axis wind turbines (SB-VAWT) based on Taguchi approach

Abstract

This research uses computational fluid dynamics (CFD) to perform a two-stage optimization of power output in multiple vertical-axis wind turbines (VAWT) with straight blades. In the first stage, four configurations are evaluated and optimized utilizing the Taguchi approach. Three operational factors, including the distance between the third turbine and the y-axis (H), the distance between the second turbine and the third turbine (B) and, placing the fourth turbine along with two levels, are considered to account for their effects on the output of the multiple turbine system. The impacts of the three factors on the performance are highlighted by H > B > placing the fourth turbine. Subsequently, based on the Taguchi-optimized combination, the analysis of the specific factor is conducted in the second stage by varying the B value. The results suggest that B = 6m without placing the fourth turbine can further intensify the power output of the VAWT system by around 3%, increasing the mean power coefficient (Cp¯) from 0.5026 to 0.5174. This is attributed to the Magnus effect, originating from the first and the second turbine. Furthermore, the results also show that changing the rotating direction of the third turbine from counterclockwise to clockwise deteriorates the output power, reducing the Cp¯ to 0.3339. Overall, the mean power coefficient of the optimized three-turbine system is higher than that of the single VAWT (Cp = 0.4473) by a factor of 15.7% under the wind speed of 8 m⋅s−1 and a tip speed ratio of 2. This reveals that the optimal design can effectively increase the output power performance of VAWT systems.