Characteristics of Offshore Wind Farm Wakes and their Impact on Wind Power Production from Long-term Modelling and Measurements

Abstract

As the penetration of offshore wind farms continues to increase in Western Europe, the North Sea in particular is becoming more densely populated by offshore wind farms. Wind turbine wakes have been a topic of great research in the field of wind energy for some time, however the industry now seeks an understanding of the in- fluence of the wake from one wind farm on the performance of a downstream wind farm. Few studies have been conducted to this end. This project will contribute to the greater work of the DTU OffshoreWake project. This master thesis will use 2018 SCADA data provided by the project partner, Vattenfall, meteorological mast data provided by BMWi and PTJ, and the author will conduct and analyse simulations using the Weather Research and Forecasting (WRF) model for the same time period. Additionally, this project will comment on the validity of the wind farm param- eterization sub-models within WRF, and investigate the dependance of wakes on climatological variables and offer a longer term study than previously conducted, therefore giving the possibility of conclusions with greater certainty based on this body of work. It is found that both of the wind farm parameterization schemes (Fitch and EWP) used in this project can reasonable replicate the trends seen in the measured data. The EWP scheme tends to over-predict both gross power produc- tion and mean wind speed, while the Fitch scheme tends to underpredict the same. However, for both schemes, good agreement is found with measurements when the wind speed is accurately predicted. Wind farm wakes are observed in SCADA data and WRF simulations. The magnitude of velocity deficit tends to increase for sea- sons in which atmospherically stable conditions are most frequent. In the region of study, these stable conditions are accompanied by generally lower wind speeds and winds which prevail from the east.