Experts explain how designers account for extreme weather.
ADVERTISEMENTA powerful tornado has swept through a wind farm in the United States, leaving a trail of crumpled power-producing towers in its wake.
Five wind turbines were destroyed by the freak weather event, with one bursting into flames.
Video of the direct hit on the wind farm near Greenfield, Iowa, show the violent twister ripping through the countryside, uprooting trees, damaging buildings and sending dirt and debris high into the air.
Several of the turbines at MidAmerican Energy Company's Orient wind farm recorded wind speeds of more than 100 mph as the tornadoes approached just before the turbines were destroyed, the company said in a statement.
“This was an unprecedented impact on our wind fleet, and we have operated wind farms since 2004,” MidAmerican said.
Is it common for weather events to destroy wind turbines?
While there have been isolated incidents of tornadoes or hurricanes damaging wind turbines, fortunately such occurrences are extremely rare, says Jason Ryan, a spokesperson for the American Clean Power Association.
Although rules vary around the US on how far turbines must be placed from other structures, Ryan said the giant turbines are not placed directly next to homes and other occupied buildings.
There are currently nearly 73,000 wind turbines in operation across the country, he said. Many of those operate in the center of the country, often referred to as the wind belt, which stretches from Texas north through Oklahoma, Kansas, Nebraska and the Dakotas, and includes large swaths of Minnesota, Iowa and Illinois.
Many of those same states are also prone to tornadoes, especially during the spring, including a portion of the Central Plains extending from the Dakotas south into Oklahoma and Texas, says Jennifer Thompson, a meteorologist with the National Weather Service in Norman, Oklahoma.
How do wind turbine designers account for extreme weather?
Wind turbines are built to withstand high wind speeds and severe weather, like tornadoes, hurricanes and lightning strikes, but few structures are designed to withstand a direct hit from a powerful tornado, says Sri Sritharan, an engineering professor at Iowa State University who has studied the impact of earthquakes and severe weather on structures.
“When you do a design, you don't design something that can withstand an EF4 or EF5 tornado,” Sritharan said.
Wind turbines are designed to meet industry standards for structural integrity that includes factors like wind speed, and it's possible that design code committees will consider the impact of Tuesday's tornado strikes in the future, he said.
“I would think they would look at this event and how they should update the standards,” Sritharan said.
