Influence of wakes and atmospheric stability on the floater responses of the Hywind Scotland wind turbines

Abstract

As the worlds first floating wind farm, one of the main technical challenges in the design phase of Hywind Scotland was the uncertainty related to wake interaction effects between the floating wind turbines. In this paper, we address this challenge by presenting an analysis of full-scale measurements from the Hywind Scotland wind farm. Measurements of the floaters' roll, pitch and yaw motions are presented, both in the form of statistical data and response spectra. The floater responses of a turbine in free wind and a turbine in wake are compared, and the influence of different atmospheric stabilities on the floater motions is investigated. Despite the large distance between the turbines of 9 rotor diameters, wake effects in the measured floater motions are observed at the downstream turbine. Furthermore, both the wake responses and the free wind responses show a clear dependency on atmospheric stability. However, overall motions are small for all wind speeds, showing that the design performs satisfactorily in both free wind and wake conditions.