Presentations

Abstract

In this study, we share results from a unique floating lidar buoy campaign in the N11-N12 area of the German Bight. The campaign consists of two buoys sited approximately 20km apart from each other with several operating wind farms to the south and southwest at distances of 15-70 km. Given the orientation of the two buoys and the neighboring wind farms, we often find that one buoy is waked from the nearby wind farms while the other buoy is not. Thus, by comparing the lidar wind speed measurements from the two buoys, we can directly measure the wind speed wake loss caused by the neighboring wind farms. Optical and radar satellite imagery during wake events provides independent verification that the measured wind speed differences are caused by the upstream wind farms and not some other external influence. These lidar buoy measurements are valuable for quantifying the impact of long-distance wakes across multiple timescales. Initial results show that the measured wake loss, i.e. the wind speed difference between the two buoys when the wind blows from the south and southwest, exceeds 1.5 m/s at hub height during individual wake events. The long-term mean wake loss is nearly 1m/s within the most affected sector where wind farms are 15km upstream. The mean wake loss is still 0.5 m/s from the sector where wind farms are more than 35km away from the buoys. Thus, wake losses are shown to be significant even from distant wind farms.  The measurement campaign will complete two years of data collection at the end of April 2026. Our final presentation will explore the seasonality of the measured wake losses and the year-to-year variability of long-distance wakes. We’re particularly interested to understand the drivers of interannual wake variability by analyzing wind direction and turbulence intensity measurements across the two years of the campaign. Lastly, we suggest that this measurement campaign design be utilized at other prospective wind farm sites with surrounding wind farms. Concurrent measurements across two (or more) floating lidar buoys enable direct measurement of the long-distance wind speed deficits caused by surrounding wind farms. These data are very valuable for bias-correcting wake model results and reducing the uncertainty of wake models. Direct measurements also allow us to understand additional facets of long-distance wakes that are not traditionally incorporated into energy assessments, including seasonal variability and interannual variability of wakes.