Multiple onshore wind turbine collapses during Iowa tornado outbreak

What happened

In May 2024 a tornado outbreak across the central United States, including Iowa, produced a tornado rated EF4 that caused fatalities, dozens of injuries and the destruction of a large number of homes in a nearby community. The same outbreak brought down several utility scale onshore wind turbines at wind farms in the surrounding rural area of Iowa. Reports stated that no site personnel or members of the public were injured by the turbine collapses themselves.

The operator stated publicly that the event had an unusually large impact on its wind fleet and that it had recorded only one previous turbine collapse, also caused by a tornado. Photographs and video of the collapsed turbines were widely circulated in news media. Publicly available reporting did not include the results of a detailed structural investigation of the failures.

Contributing factors

As reported in the source: (1) the tornado was rated EF4 by the national weather service, corresponding to wind speeds in the region of 166 to 200 mph; (2) utility scale wind turbines are designed against standards for extreme sustained wind loading and are not designed to survive a direct tornado strike, the tornado wind field differing from the design wind regime in peak velocity, gust profile and rotational loading; (3) the operator's statement that only one comparable collapse had occurred previously indicates that direct tornado strikes on turbines are rare even in tornado prone regions. No detailed failure analysis of foundations, tower sections or connections was reported publicly.

Lessons learned

1. Utility scale onshore wind turbines are not designed to survive direct EF4 tornado strikes, so operators in prone regions should record tornado exposure in site selection and risk assessments.
2. A single tornado can collapse several turbines at once, so portfolio risk assessments should test correlated multi site loss from clustered wind farms.
3. Direct tornado strikes on turbines are rare, so operators should still plan for the event based on the single prior collapse recorded by the same operator.

More lessons on design, standards and commissioning, structural integrity and turbines, from every incident on the register.

Not yet known

• Detailed structural investigation results
• Turbine models and ages
• Downtime and repair costs

This entry is updated when these are reported. Get an alert for the next one like it.

Source

thewellnews.com