Cost Analysis of a Condition Monitoring System for Journal Bearings in Wind Turbine Gearboxes

Abstract Journal bearings (JBs) have become an established technology in planetary stages of wind turbine (WT) gearboxes, offering high torque density, and reliable operation. Since their introduction into serial production, they have demonstrated robust performance. However, abnormal operating conditions such as contamination, dry running, or elevated local temperatures can cause bearing seizure and costly gearbox failures with extended turbine downtime. Condition monitoring systems (CMS) provide an opportunity to detect critical operating states at an early stage and to initiate countermeasures, thereby preventing catastrophic failures, reducing repair costs, and mitigating yield losses. Despite this potential, no commercial CMS dedicated to WT gearbox JBs is currently available, and existing approaches remain subject to research. This work investigates the benefit of implementing a CMS for JBs in WT gearboxes regarding economics. First, the study quantifies the costs of gearbox failures, including replacement and yield losses, based on a literature review. Second, it estimates the capital expenditure associated with integrating a CMS. By combining these inputs, a cost model is developed to assess whether the CMS can achieve positive net present value. The model accounts for differences in WT location, failure rates, power ratings, and gearbox configurations, including the number of planetary gears per stage. The paper concludes with a sensitivity analysis of the model and a scenario analysis that shows when the use of a CMS is economically justified. The analysis shows that the CMS application is more beneficial in the offshore sector than in the onshore sector. A maximum acceptable CMS cost value of 1.000 € is set as the limit so that the application makes economic sense in both cases. The analysis shows that the use of CMS only brings economic benefits if the bearing failure rates are significantly higher than 0.0007 /(WT∙year).