On maintenance optimization for offshore wind farms

Doctoral thesis, 2013

The maintenance cost is known to be an important part of the levelized cost of energy generated by wind parks. Operational costs can be significantly reduced by optimizing decisions for maintenance strategies, maintenance support organization and maintenance planning. This is especially important for offshore wind power systems to reduce the high economic risks related to the uncertainties in the accessibility and reliability of wind turbines. This thesis proposes decision models for cost efficient maintenance for offshore wind power systems. The economical benefits of condition based maintenance strategies are evaluated for drive train and for blades of wind turbines. A model is presented to optimize the inspection interval for the blades. Models are proposed to perform cost-benefit analysis of the maintenance support organization by evaluating the benefit of logistic and personnel planning on availability. The maintenance planning of service maintenance activities is optimized by taking advantage of opportunities arising at low wind or when corrective maintenance activities are necessary. The models are tested in case studies with real environmental, reliability and cost data when available, and sensitivity analyses are performed for the parameters of interests. The results show that the proposed models can be used to reduce the maintenance costs through optimizing the maintenance strategies, the support organization and the maintenance planning.