Optimal Maintenance Strategy for Wind Power Plants

  Maintenance strategy without inspections (Source: FCN/B. Kerres; FCN Study Thesis)

Wind power is a relatively young but nevertheless rapidly growing source of electricity production. The costs for operations and maintenance (O&M) of wind turbines make up a significant part of their life-cycle costs, with some potential for optimization. Maintenance planning can be done by using qualitative or quantitative methods. However, a comparative cost-benefit analysis of different maintenance strategies has to use a quantitative approach. In this research project, we develop a model for estimating the costs and reliability as a consequence of the maintenance strategy performed.

The maintenance model developed consists of two major parts, a wind turbine and a service team. The wind turbine is modeled as a series connection of important components which fail according to a stochastic process. The service team carries out maintenance at the turbine according to a given set of rules, the maintenance scenario. The model calculates the costs of the maintenance actions, while the wind turbine availability, together with power prices and wind speeds, are used to calculate the revenues from the turbine. The trade-off between higher maintenance costs and higher downtimes is evaluated in order to rank the strategies in their order of cost-effectiveness.

As an illustration of the model’s viability, we perform a case study for a Vestas V44-600kW turbine. Specifically, we use the results of a reliability-oriented maintenance analysis of this wind turbine for identifying important components and deriving possible maintenance scenarios. The wind turbine reliability and maintenance cost model then calculates income and cost distributions for different maintenance scenarios with the help of Monte Carlo simulation. Finally, by comparing different maintenance scenarios for several wind turbine components, we find that in the V44 case study the components investigated are best serviced by a runto- failure strategy.