Effect of Leading-Edge Slot Blowing on a Vertical Axis Wind Turbine

An analysis of vertical axis wind turbines, subjected to flow control by means of leading-edge slot blowing, was performed. The analysis was based on blade-element momentum theory that included experimental data acquired on a NACA 0012 airfoil subjected to a wide range of blowing momentum coefficients. Two methods of control were considered: single-sided slot blowing that was active on either the upwind or downwind halves of the turbine disk or double-slot blowing applied on both upwind and downwind sides. The net turbine power output was calculated by accounting for the pumping power required to drive the slot-blowing system, including secondary system losses. The system could be optimized by employing blowing selectively below predetermined blade tipspeed to windspeed ratios or above the blade stall angle only. The results show significant potential for flow control by jet blowing using all methods and approaches. Single-sided blowing resulted in a 59% increase net energy yield, while double-sided blowing produced improvements in excess of 150%, even when secondary system losses were factored into the estimates.