Robust Tower Fairings to Mitigate the Tower Shadow Effect for Extreme Downwind Turbines

Motivated by manufacturing larger, more efficient, low cost, wind turbines, designers are considering downwind rotors. A downwind two-bladed rotor can produce equivalent power at a fraction of the cost compared with conventional upwind three-bladed rotors. The largest design obstacle for downwind rotors is the tower shadow effect, the aerodynamic effect that the tower wake has on the downwind rotor. The tower shadow effect can be mitigated by the use of an aerodynamic fairing to cover the tower. When designing a tower fairing, because in operation wind turbines will experience wind from varying directions, one should consider the fairing effectiveness at a variety of flow angles. Three tower fairings, with varying degrees of trailing edge roundness, were designed and experimentally characterized at misalignment angles, 0°, 10° and 20°. All three fairings significantly reduced the tower shadow effect at 0° misalignment angle, but only one fairing, the E863r45, reduced the tower shadow effect at misalignment angles as large as 20°. Of the fairings tested the E863r45 fairing is the most robust and recommended for applications where tower shadow reduction is necessary for a range of flow angles.