Offshore Wind Energy Analysis of Cyclone Xaver over North Europe

Cyclone Xaver (5 December 2013; North Sea) was an extreme weather event which affected northern Europe, yielding a record of wind power generation. The most striking aspects of this atmospheric phenomenon were the gale-force winds and the upcoming abrupt increase of the wind power over the North Sea. The main objective of the study is the analysis of the impact of Xaver on offshore wind power production. In this way, the WRF numerical model was used to simulate the cyclone in a fine horizontal resolution (5km x 5km). The focus of the simulation is on the extended region of the North Sea and the Baltic Sea. The evaluation of the model outputs against observational data from 3 offshore locations denotes a sufficient agreement (SI≈0.12) and supports a realistic analysis of the wind field. The simulation exposed much higher values for wind speed over the North Sea compared to the neighboring regions during the passage of the cyclone. The wind speed at the 100 m level ranged within 11-25 m/s (rated output wind speed) for 40 hours over the North Sea and 70 hours over the Baltic Sea. On the other hand, the wind speed at 100 m exceeded 25 m/s (cut out wind speed) for ca 30 hours over the North Sea. In addition, comparison of wind power density between two different height levels (100 m and 200 m) is presented. The model results indicate 15% to 20% higher wind power density at 200 m than for 100 m for the largest part of the North Sea. For some regions the difference exceeds 25%.