Posts overstate tornado risks to wind turbines

"This is what tornados do to wind turbines," a May 23, 2024 Facebook post says linking to a video of a wind turbine being snapped in half during a tornado that claimed the lives of at least five people in Iowa. 

Similar claims questioning why a location prone to tornadoes would support wind farms spread on X here, here and here as residents were surveying damage across Adair and Adams counties.

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A screenshot of a Facebook post taken on May 24, 2024

Iowa relies heavily on renewable energy and is the second-largest wind power producer in the United States after the state of Texas (archived here).

Tornadoes do impact the state and local media reported that the May 21 storm destroyed ten wind turbines (archived here and here), but experts said this level of damage is atypical.

"For the record that's 10 out of 6,757 turbines in the state, per the Energy Information Administration," said Kanan Kappelman, a spokeswoman for the Iowa Economic Development Authority. 

"It is unusual for wind turbines to suffer tornado damage," she told AFP on May 23.

MidAmerican Energy, which has been operating in the state since 2004, also said this storm triggered an "unprecedented impact" to its wind fleet. 

"We have experienced only one other instance of a wind turbine collapse, which was also caused by a tornado," Tina Hoffman, a spokeswoman for the company, told AFP on May 24.

Video of turbines withstanding tornadoes have also been captured (archived here).

Powerful winds

Tornadoes are measured on the Enhanced Fujita Scale or EF Scale and rated based on wind speeds and damage (archived here).

The National Weather Service said it confirmed "EF-4 damage in Greenfield, Iowa, EF-3 damage in NW Adams County, and EF-2 damage from two tornadoes: in Polk into Story County and near Arbor Hill " (archived here). The top wind speeds in the EF-4 tornado were estimated at 175-185 miles (281.6-297.7 kilometers) per hour.

Manufacturers design wind turbines to sustain extreme weather including severe thunderstorms and high wind events, but Hoffman said: "Few structures can withstand a direct hit by a powerful tornado such as what we experienced on Tuesday."

She said several of the company's turbine sensors registered wind speeds over 100 miles (160.9 kilometers) per hour as the tornado approached, before the towers were destroyed.

Sanjay Raja Arwade (archived here), professor of civil engineering at the University of Massachusetts Amherst, told AFP the probability of a tornado directly impacting a tower is very low.

"The amount of land area that a given tornado impact is relatively small," he said on May 24.

Turbine operators also take percautions, such as designing the systems to automatically shut off at very high wind speeds (archived here).

Legislation in Iowa requires wind turbines to be placed at a minimum distance from inhabited areas in order to reduce risk to human safety in case of a catastrophic event (archived here). 

But turbines, "like any other piece of infrastructure including buildings, can be damaged by a direct hit by a tornado," a spokesman for the Department of Energy told AFP on May 23.

By the end of April, tornado reports in the United States had already largely surpassed the 1991-2020 annual average, setting the scene for one of the most active years on record (archived here).

But Arwade said: "If you look at all of the wind turbines across Texas, Oklahoma, Nebraska, Iowa, all the Great Plains states, the number of those turbines that are going to be impacted in a given tornado season is small. Even with incorporating the effects of climate change, it is going to remain small."

AFP has debunked other claims about wind turbines, here and here.