Reconsidering downwind operation by analysis of the National Renewable Energy Laboratory’s Phase VI data

Power was not reduced as expected for downwind, which may be attributed to inboard three-dimensional effects. Average flap bending loads were reduced with downwind coning and compared well with prediction.

Fatigue loads were increased with downwind; however, fatigue was mitigated with a tower shroud. The shroud needs to align with the freestream, demonstrated by an increase in fatigue loads from a 10° shroud misalignment. Pressure data were acquired in the tower wake at the rotor location with and without the shroud.