Presentations

Abstract

Wakes from neighbouring wind farms, either operational or yet-to-be-built is understood to have a significant impact on project yield.  However, most discussions on this topic rely on numerical modelling studies to understand their impact. In this study, Two floating lidar measurement systems “A=North West” and “B=South East”, located in the N12 and N11 areas respectively, have been used to analyse wakes from producing windfarms in the N6, N7 and N8 area of Germany. During periods when wind directions originate from behind the existing projects, windspeed measurements at B (situated 15-22km from the operating projects) are lower by an annual average of 1.2m/s at hub height compared with A.  During periods when the wind directions originate from unwaked sectors, the windspeeds at A and B are within 0.3 m/s. To help ensure that the observed windspeed difference is caused by the upstream wind farms, satellite imagery was screened to identify precise moments where wakes can be observed stretching towards the B measurement location.  A specific moment was clearly identified on 2025-04-29 at 10:55:56, where climate conditions allow for wake disturbed low cloud to be visible to the satellite, and clearly persisting to floating lidar B (but not A).   We can be confident that at this moment, any delta between the two measurement stations is derived primarily from the wake effects of the neighbouring windfarms. At this timestamp, the windspeed difference between A and B is 1.7m/s at 140m (10.51ms vs 8.82ms).  Looking across the day, where windspeeds persist from the direction of the existing windfarms, a consistent ~1.5-2m/s delta is present at this height as windspeeds fluctuate between 11 and 5m/s.  When the wind direction changes, the difference between the two measurements returns to negligible.