A stochastic fleet size and mix model for maintenance operations at offshore wind farms

•We consider a new maritime fleet size and mix problem arising for offshore wind farms.•Uncertainties in vessel price, weather, electricity price and failures are considered.•A new three-stage stochastic programming model is proposed.•The model is solved as its scenario tree node-based deterministic equivalent.•Results show that it is valuable to incorporate uncertainty in the modeling approach.

A fleet of vessels and helicopters is needed to support maintenance operations at offshore wind farms. The cost of this fleet constitutes a major part of the total maintenance costs, hence keeping an optimal or near-optimal fleet is essential to reduce the cost of energy. In this paper we study the vessel fleet size and mix problem that arises for the maintenance operations at offshore wind farms, and propose a stochastic three-stage programming model. The stochastic model considers uncertainty in vessel spot rates, weather conditions, electricity prices and failures to the system. The model is tested on realistic-sized problem instances, and the results show that it is valuable to consider uncertainty and that the proposed model can be used to solve instances of a realistic size.