the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 24 Oct 2025
Reliability and O&M key performance indicators of onshore and offshore wind turbines based on field-data analysis
Abstract. Based on maintenance data from over 1000 onshore and offshore wind turbines covering more than 4200 operating years, this study presents an analysis of failure rates, repair times, and maintenance resource requirements, focusing on subsystem-level reliability. Failure rates per turbine and megawatt are compared and failure behaviour over time is examined. Next to failure events, further corrective and preventive maintenance interventions are analysed. To provide more detailed insights for operation and maintenance simulations, a distinction is made between total major component replacements and those specifically requiring a jack-up vessel. Results show that onshore wind turbines have higher failure rates per megawatt than offshore wind turbines. Key subsystems including the pitch system, the control system, and power converter system are identified as critical to overall wind turbine reliability for both onshore and offshore wind turbines. For the overall wind turbine system, a failure behaviour over time following a bathtub curve is identified, with distinct trends for individual subsystems.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Wind Energy Science.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: open (until 12 Feb 2026)
- RC1: 'Comment on wes-2025-212', Anonymous Referee #1, 30 Dec 2025 reply
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RC2: 'Comment on wes-2025-212', Anonymous Referee #2, 24 Jan 2026
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This paper provides recent, detailed field data on the reliability of modern onshore and offshore wind turbine systems. The data and analysis help to advance understanding of failure rates and development of maintenance strategies. The paper could be improved by providing greater detail to describe the population of turbines in the dataset (without breaching confidentiality requirements). Specifically, it would be valuable to include figures or tables that show the distribution of rated capacities among onshore and offshore turbines, the distribution of turbine ages (operational years), and the shares of technology type such as geared/direct drive/hybrid.
In the presentation of results, please provide more discussion of the difference between failure rates per MW and per WT. Comparison of Figs. 1 & 2 would seem to indicate that for some components (e.g. MDA, MDY) the failure rate is relatively constant per WT whereas other components (e.g. MDL, MDX) appear to have a constant rate per MW. It would also be helpful to note the average rating of onshore and offshore WTs.
The comparison of failure rates across OEMs does not add much value because the OEMs must remain anonymous. A comparison across characteristics that could be identified (such as drivetrain concepts or generator types) would have more value to researchers interested in using this paper to identify areas for future study or application of new maintenance strategies.
The comparison of results for onshore WTs with previous studies would benefit from more explanation of the differences between turbine populations, for example, normalizing by rated power as you have done for offshore WTs.
Please define major component replacement in the context of this paper. Do you use a size or cost threshold to identify MCRs?
Table 2 is unnecessary, the contents are already present in the preceding paragraph.
Citation: https://doi.org/10.5194/wes-2025-212-RC2
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