Derating a wind turbine is a strategic move sometimes made by an operator to extend the life of an asset, moving potential failures from one fiscal year to the next.
Derating refers to lowering the maximum power output of the turbine to reduce loads on the gearbox and mitigate damage growth. The loss of energy production is offset by prolonging the need for a full gearbox replacement.
Use case example: Sentient de-rate recommendation results in 17 month life extension of “Asset 12,” a 2.5MW-rated machine.
Based on Sentient’s prognostic simulations, we recommended that the operator inspect Asset 12 on December 5, 2014, listing it as #11 on the Critical Turbine Watch List. After borescope inspection on December 8, 2014, the operator confirmed Sentient’s damage prediction.
Sentient recommended an optimal de-rate of 80% to 2 MW on March 23, 2015 to extend gearbox life by 6 months. The operator did a second borescope inspection on September 2, 2015 where Sentient recommended an additional de-rate to 70% or 1.75MW output to extend life further by 4 months. In Dec. 2015, Sentient recommended a change to the oil filter that had been changed 6 months prior in June due to metallic debris. The customer and Sentient chose to further de-rate Asset 12 to 50% or 1.25MW output for another 7 months of life extension. Overall life extension achieved on Asset 12 was 17 months.
The calculated ROI from the de-rated machine showed to be more profitable to the operator than it would have been to from the loss of production during downtime and costs incurred from a catastrophic gearbox failure. The de-rate in this instance helped the operator extend Asset 12’s life until proper budgeteding was available.