A Markov-Chain-Based Availability Model of Offshore Wind Turbine Considering Accessibility Problems

Availability of wind turbine (WT) is an essential parameter both for wind project feasibility analysis and operation and maintenance optimizations, but in offshore wind farms, it is greatly affected by accessibility which has been seldom considered in traditional reliability evaluations. This paper presents a Markov-chain-based availability assessing model of offshore WT considering accessibility problems. Based on the procedure analysis of corrective maintenance offshore, the contribution of poor accessibility to availability is summarized into two independent aspects: stochastic offshore weather and inadequate maintenance resources. A three-state model of offshore WT is established. A Poisson-process-based algorithm is presented to calculate a transition rate of the three-state model. A three-integer field representing a wind farm with NWT WTs is defined for the Markov chain. Mean availability of WT is obtained by solving a Markov transition matrix. The results of case study show that the proposed model provides an effective approach for the availability assessment of WT in a multi-turbine wind farm influenced by stochastic offshore weather and different logistic policies.