Optimization of hydrofoils for a bidirectional tidal stream turbine

Abstract Tidal stream turbines present an appealing approach for consistent renewable energy generation. Capitalizing on the periodic nature of tidal streams, these turbines can be designed to function bidirectionally, eliminating the need for a yaw control system. Although airfoils and hydrofoils in general have been extensively studied, there is less work available on bidirectional designs. Through the use of optimization methods, this work introduces bidirectional hydrofoils of varying thicknesses with improved performance compared to elliptic profiles. The optimization was performed using the hydrodynamic efficiency as the objective function, with simulations performed using 2D computational fluid dynamics. The optimized hydrofoil was then used in a turbine design, which is simulated using blade element momentum theory. The hydrofoils showed an improvement in hydrodynamic efficiency of up to 10 %. In the turbine design, this resulted in an improvement of 5.3 % in power coefficient and a reduction in thrust coefficient of 13.2 %. The new line of hydrofoils are promising for use in cost-effective and reliable tidal stream turbine designs.