Offshore wind turbine sub-assembly failure rates through time

O&M costs can make up to 30% of the lifetime CoE of an offshore wind farm [1]. As a means of reducing this cost operators and O&M providers need a greater understanding of what is driving that O&M cost. Failure rates of wind turbines and their components are a key driver of O&M costs. Past papers have modelled O&M costs assuming a fixed average failure rate for wind turbine subsystems [2]. This work aims to determine if it is accurate to assume a fixed failure rate or if a failure rate distribution through time can be provided to allow for more accurate O&M cost modelling and in turn CoE modelling. This paper shows the results of an analysis of offshore wind turbine annual failure rates over an 8 year period. The analysis is based on around 350 modern multi MW offshore turbines located in 5-10 offshore wind farms throughout Europe. The literature review for this paper indicated that a constant average failure rate should only be used if the shape parameter of the failure distribution is around 1. However results from the failure rate analysis in this paper have shown that in many cases a constant failure rate is not correct for O&M Modelling.