O&M cost modelling of major replacements in next-generation offshore wind turbines

When using large, 15MW next-generation offshore wind turbines, the choice of turbine drive-train configuration has the potential to significantly impact the cost associated with the major replacement of large wind turbine components over the wind farm lifetime. This paper presents an O&M cost modelling analysis of major replacement tasks across a range of site locations and major replacement rate scenarios using both 15MW direct-drive and 15MW medium-speed turbine configurations. Using an existing, previously benchmarked offshore wind O&M model and major replacement rate values previously estimated for 15MW next-generation offshore wind turbines using structured expert elicitation, the total cost of major replacement tasks, consisting of vessel cost, repair cost and lost electricity cost, is estimated for three case study locations and three different major replacement rate scenarios using both turbine configurations. It was found that, across all scenarios, the medium-speed turbines achieved a lower cost associated with large component major replacement tasks, driven mainly by the lower component costs of the medium-speed generator and gearbox compared to the expensive direct-drive generator.