TNO research improves damage prediction for wind turbine blades
A large part of the damage to offshore wind turbines occurs in just 12 hours of the year, under specific weather conditions.
Published on March 22, 2025
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Wind turbines in the North Sea have to deal with extreme weather conditions that cause blade erosion. The PROWESS study, led by TNO, shows that a substantial part of the damage to offshore wind turbines occurs in only 12 hours of the year under specific weather conditions. With new insights from this study, the wind energy sector can save millions of euros in maintenance costs through preventive measures.
PROWESS stands for PRecipitation atlas for Offshore Wind blade Erosion Support System, a project in which wind farm operators such as Eneco, Shell and Equinor collaborated.
Weather measurements on the North Sea
For a year, TNO took detailed precipitation measurements in the North Sea. Analysis of this data showed that approximately 30% of the annual erosion damage to wind turbine blades occurs in just 12 hours of the year. This happens at times when strong winds and intense rainfall coincide.
The damage, known as Leading Edge Erosion (LEE), occurs when the tip of the wind turbine blade reaches the maximum speed of 325 km/h (90 m/sec) with wind speeds from 63 km/h (10 m/s) and more than 7.5 millimeters of rain per hour.
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“We already knew that heavy rain has a major impact on the rotating turbine blades, but the fact that almost a third of the erosion damage was caused in such a short period was a new insight,” says Harald van der Mijle Meijer, a wind energy researcher at TNO. “With this knowledge, wind farm operators can now preventively lower the speed of the turbines to prevent serious damage, which can lower maintenance costs. Because damage is less likely to occur in the first place because it is easier to estimate when the speed of the wind turbines needs to be lowered.”
Erosion radar
TNO used new measuring methods to obtain detailed data about wind and rain. “For example, we also wanted to know the size of the raindrops because this determines the erosion damage to the rotor blades,” says van der Mijle Meijer. Disdrometers, sensors that measure the size of raindrops, were placed at various locations in the North Sea. These measurements were used to analyze potential erosion and validate existing radar data. TNO and its partners developed an 'erosion atlas' based in part on the research and using weather simulations with a model created by the Whiffle company that predicts where and when wind turbine blades will sustain damage from rain. The erosion atlas now enables wind farm operators to better estimate when they need to take preventive measures.
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