Analysis of wind and wave data to assess maintenance access to offshore wind farms

For offshore wind farms, maintenance operations are only possible under specific weather conditions. This has a strong impact on farm availability: given a failure, there is a chance that the maintenance crew is not able access the site safely, but has to wait for appropriate weather conditions to arise. To model the uncertainty in offshore wind farm availability growth, which is our ultimate goal, we require a probability assessment of weather windows of specific durations. This paper presents the analysis of wind and wave data collected at an offshore wind farm in the North Sea and discusses how we might extract weather window and waiting time information to support availability growth modelling. We examine the statistics of the waiting time associated with different levels of maintenance of various subassemblies of the wind turbine. Wind and wave limitations assosiated with a given maintenance operation will be critical factors in determining the level of access available to the wind farm and it is shown that slight improvement in vessel capability can result in significantly reduced waiting times and greater access.