Wind Turbine Wake-Redirection Control at the Fishermen's Atlantic City Windfarm

In this paper, we will present our work towards designing a control strategy to mitigate wind turbine wake effects by redirecting the wakes, specifically applied to the Fishermen's Atlantic City Windfarm, proposed for deployment within the next few years off the shore of Atlantic City, New Jersey. As wind turbines extract energy from the air, they create low-speed wakes that extend behind them. Full wake recovery to the undisturbed wind speed takes a significant distance. In a wind energy plant the wakes of upstream turbines may travel downstream to the next row of turbines, effectively subjecting them to lower wind speeds, meaning these waked turbines will produce less power. Wakes can be redirected laterally to some degree, though, by applying yaw misalignment to the wake-generating turbine (i.e., not pointing the turbine directly into the wind). Yaw misalignment causes part of the rotor thrust vector to be pointed in the cross-stream direction, deflecting the flow and the wake in that direction. Yaw misalignment reduces power production, but the global increase in wind plant power caused by decreased wake effects creates a net increase in power production. With the increase in power can come an increase in fatigue loads, though, caused by yaw misalignment. However, if misalignment is applied properly, and it is layered with individual blade pitch control, the load increase can be mitigated. To explore the idea of wake redirection, we used high-fidelity computational fluid dynamics. Our computational fluid dynamics simulations predict that when winds are aligned with the row, which is one of two predominant wind directions, wake-redirection control can create a 10% increase in energy capture efficiency. This means that, for a given wind energy plant's electrical generating capacity, if wake-redirection control were employed, turbines could be more closely spaced, thereby reducing the watersheet area of the wind plant. Likewise, for a given watersheet area, the total electrical generating capacity can be increased. In this paper, we discuss the concept of wake redirection through wind turbine yaw misalignment and present our computational fluid dynamics results of the Fishermen's Atlantic City Windfarm project. We also discuss the implications of wake-redirection control on annual energy production and fatigue loads, as well as plans to implement wake-redirection control at Fishermen's Atlantic City Windfarm when it is operational-something not done before at a commercial wind plant.