VESSEL FLEET OPTIMISATION FOR OFFSHORE WIND POWER MAINTENANCE

Sammanfattning: Wind power has been a leading energy source in the renewable energy sector. The offshore wind power industry is rapidly growing, having the advantages of great wind resources, with minimum impact on residential areas; however, the high O&M costs add significantly to the LCOE, and present a challenge to the project developers and operators. The objective of this Thesis is to develop an optimisation method aiming to optimise the O&M vessel fleet in terms of its size and mix, and implement it into a spreadsheet-based tool. At first, a review on the available literature was conducted, in order to establish the theoretical background on the topics of maintenance, optimisation and O&M vessels, and identify the O&M strategies used in offshore wind power. The optimisation method developed focuses on the implementation of different O&M strategies,and is mainly based on the vessel contracts strategy, which aims to acquire lease contracts of various vessel types, including helicopters, available in the market to support the maintenance activities of an offshore wind farm. The model developed consists of calculation modules and introduces a 5-stage weather data filtering process for the estimation of the operational weather window, a WT components' failures forecast method, and a 2-stage optimisation process. The model was applied on a case study of a fictitious offshore wind farm, by using measured and realistic input data, in order to examine its efficacy. The model's outputs generated presented the optimal O&M vessel fleet for three different scenarios (mean, best case, and worst case), together with the optimal allocation of the failure repairs to each O&M vessel, and the corresponding O&M costs.