Maximizing wind turbine life-cycle profitability through an optimal preventive maintenance strategy

This paper presents a novel periodic preventive maintenance (PM) strategy for wind turbines (WT) of a wind farm located in southern Morocco. The production rate is affected by the degradation state and the age of the WT. Preventive maintenance ensures age reduction such that the lower the virtual age after the i th PM (more reliable equipment), the greater the energy produced during the subsequent PM period. The maintenance department must decide how often preventive maintenance should be performed and at what level of effectiveness. The latter is determined by selecting one of five packages of maintenance tasks to be performed. Each package has a given cost and effectiveness. The more effective, the more costly, but the lower the virtual age, resulting in a higher production rate. The objective is to find the right balance between the effectiveness to be adopted for each PM, the PM period, and the production and revenue loss due to aging. To achieve this goal, a mathematical model is developed to express the expected total profit over the operating life of the WT. This profit is the difference between the revenue generated by the energy produced and the cost of preventive maintenance and repairs. A numerical iterative procedure is used to simultaneously determine the optimal maintenance period and the maintenance package (effectiveness) to be applied for each PM in order to maximize the expected profit. A sensitivity analysis is performed to illustrate the impact of variation of key operational and economic parameters on the optimal policy.