On the wake dynamics, flow loading and power output of wind farms under wake steering control: a wind tunnel experiment

Wake steering control strategies have proven to be effective for increasing the power output of a wind farm. The variation of yaw angles of individual turbines within a wind farm produces distinctive impacts on the wake flow characteristics, and therefore alter the mean/fluctuating wind loads and power outputs of downstream turbines. In this work, systematic wind tunnel experiments were performed to evaluate the performance of modeled wind farms with 3 rows and 3 columns under aligned/staggered layouts and various wake steering control strategies. Results show that the change of upstream turbines yaw angles effectively increases the downstream wake flow velocities, especially within the rotor heights. The maximum wind farm power output can increase up to 8.5% with the yawing of first and second rows in the same direction for aligned wind farm, while the impacts of wake steering control on staggered wind farm is less distinctive. Measurements on the instantaneous wind loading of turbines in the first row reveal that the growth of yaw angle significantly increases the fatigue loading in the side-force direction across all frequency components.