Smart pro-active pitch adjustment for VAWT blades: Potential for performance improvement

Vertical-Axis Wind Turbines are an appreciated design for small-scale units (Re < 5*105, P < 15 kW), with demonstrated reliability and performance levels comparable, at such scales, to horizontal-axis design and also present significant benefits (no sensitivity to wind direction, simple construction). However, the fluid dynamics performance is limited by operating the airfoils at limited Reynolds numbers (10^4 < Re < 5*105), consequently with a poor response to high incidence conditions. A potential improvement is to use morphing blades, or – as a starting point – to reduce dynamically the angle of attack through pitch adjustment. A multiple-stream tube double-actuator disk model, including dynamic stall treatment, was modified to evaluate the effect of different possible control laws for dynamic pitch adjustment. The results show that the margin for performance improvement is relevant, and that a moderate amplitude of pitch excursion can be sufficient, which is technically feasible using fast-response actuators.