Optimization and performance study of bidirectional Savonius tidal turbine cluster with deflectors

Savonius vertical axis tidal turbines (S-VATT) show potential utilization in bidirectional tidal regions because of the high start-up characteristics and coupled enhancement effects. Previous studies suggested that deflectors can significantly improve the power output of the isolated turbine and cluster. However, few studies focus on the deflectors installed on the bidirectional S-VATT cluster. This study proposed a deflector system for a bidirectional cluster and used the Kriging method combined with genetic algorithm to optimize the configuration of deflectors. The optimization study showed that the optimized cluster has a power coefficient improvement of 34.5 % compared with the cluster without deflectors. The flow mechanisms of the optimized cluster were analyzed by mean and transient flow fields, which reveal that deflectors could reduce the high-pressure area at the returning blade and increase the low-pressure strength and area at the advancing blade. The effect of tidal direction on the optimized cluster was investigated, and the results showed that the cluster has a high efficiency with a flow angle range of 60 degrees. Finally, this study developed a four-turbine cluster using the configuration of the optimized cluster, and the results showed a power improvement of 22.7 % to the four-turbine cluster without deflectors. In sum-mary, this study provides a high-efficiency cluster with deflectors that maintained a potential to be developed into a large-scale farm installing bidirectional tidal regions.