A tandem mother-daughter-vessel routing problem for maintenance activities in offshore wind farms

This paper studies an innovative but complex transportation problem in offshore wind farms to improve operations and maintenance. The problem comprises a service operation vessel and safe transfer boats in a tandem configuration. The service operation vessel is referred to as the mother vessel, which may be equipped with multiple safe transfer boats known as the daughter vessels. The aim is to obtain optimal or near-optimal routes for both the vessels to drop and pick up technicians and equipment to maintain the service quality of the selected offshore turbines to minimize the total cost. A new mixed-integer linear programming model is first designed and tested on small instances. As the model becomes inappropriate for medium and large instances, an effective metaheuristic based on variable neighborhood search, equipped with powerful local searches and effective speed-up mechanisms, is then developed. Our approach is assessed using available realistic instances, which yields interesting managerial insights. Additionally, as there are no benchmark solutions for this new problem, the performance of our method is benchmarked against existing state-of-the-art methods for a related drone routing problem. The computational results indicate that our approach is powerful and flexible enough to outperform these well-known methods.