18 Jan 2022
18 Jan 2022
Status: a revised version of this preprint is currently under review for the journal WES.

Offshore wind farm cluster wakes as observed by a long-range scanning wind lidar

Beatriz Cañadillas1,2, Maximilian Beckenbauer1, Juan José Trujillo2, Martin Dörenkämper3, Richard Foreman2, Thomas Neumann2, and Astrid Lampert1 Beatriz Cañadillas et al.
  • 1Institute of Flight Guidance, Technische Universität Braunschweig, Germany
  • 2Renewables, UL International GmbH, Oldenburg, Germnany
  • 3Fraunhofer Institute for Wind Energy Systems, Oldenburg, Germany

Abstract. To establish long-term flow measurements for the validation of wake models, a scanning Doppler wind lidar system was installed at the western edge of the wind farm Gode Wind 1 in the German Bight for a period of five months. The main goal was to detect the wakes from clusters for different wind directions and atmospheric stabilities. The lidar data are categorized into five sectors based on the different upstream conditions. The influence of wakes and atmospheric stability are initially investigated with respect to airborne measurements collected within the lidar measurement period. Mesoscale simulations are used as a reference for the free wind flow. The percent wind speed difference downstream of the wind farm clusters and at the location of the scanning lidar measurements (1.5 km downstream the closest wind farm) can reach a maximum of about 30 % for a mean wind speed of 10 m s−1 depending on the wind direction and under stable atmospheric conditions. A good agreement between mesoscale simulations (without any wind farm parameterization) and lidar measurements is found for undisturbed wind sectors and unstable and near-neutral atmospheric conditions. By taking into account the surrounding wind farms through a parameterization in the mesoscale simulations, the agreement of the model with the measurements is relatively good for unstable and near-neutral conditions, including sectors influenced by wind farm wakes. For stable conditions, however, the highest discrepancies between simulations and observations occur. Overall, the scanning lidar dataset can be used as a validation tool for wake model validations.

Beatriz Cañadillas et al.

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Beatriz Cañadillas et al.

Beatriz Cañadillas et al.


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Short summary
Lidar measurements combined with meteorological sensors reveal the strong directional and stability dependence of the wake strength in the direct vicinity of wind farm clusters.