An adaptive yaw method of horizontal-axis tidal stream turbines for bidirectional energy capture

Tracking the flow direction is one of the effective ways to harvest more energy for a horizontal-axis tidal stream turbine (HATST). This paper presents a novel HATST design that incorporates a yaw method with a tail wing, inspired by horizontal-axis wind turbines. The design enables the HATST to adaptively yaw toward the bidirectional flow with a reciprocating rotation. To ensure stability, a small yaw angle was reserved and permanent magnets were employed to hold the yaw mechanism steady. The kinetic equations of the yaw mechanism were established, and the influence of the yaw shaft's position and the tail wing's mass on the yaw performance was analyzed. A test model was constructed to validate the design and analysis, and the optimum parameters were discussed. Experimental results demonstrated that the HATST yawed well toward the inflow and maintained the designed yaw angle of approximately 5 degrees at different velocities. Compared with the device without magnetic assisted yaw, the HATST achieves more than 4.47% increase in output power in the velocity range of 0.15 m/ s to 0.31 m/s, and exhibits minimal swing amplitude. This research provides a novel and practical solution for the effective utilization of bidirectional tidal steam energy.