Optimal post-warranty maintenance contracts for wind turbines considering availability

Outsourcing maintenance is an economical way for wind farm owners to address sophisticated and expensive maintenance operations of wind turbines. This paper proposes three options for the post-warranty maintenance contract of wind turbines from the perspective of service providers. Option 1 involves corrective maintenance only. In option 2, the first preventive maintenance is performed at a certain time point and after that periodic maintenance is carried out. Option 3 initiates with a preventive replacement and performs periodic maintenance subsequently. An availability target is set over the contract period and failing to satisfy the target incurs a penalty from the service provider. The objective is to determine the optimal preventive maintenance programs of option 2 and option 3 that minimize the contract servicing cost. Numerical examples are provided to illustrate the proposed policies. The results show that option 2 and option 3 are more effective than option 1 and their effectiveness grows when warranty and contract coverages increase.