Causes of turbine failures remain a mystery 

NextEra Energy, owner of the Steele Flats wind farm in southern Nebraska, has suffered at least four wind turbine calamities in recent weeks, including broken blades, a fire and a collapse.

Steven Stengel, a spokesman for the Juno Beach, Florida-based energy company, said the incidents are under investigation in cooperation with the turbine manufacturers, but it could be weeks or months before they figure out causes. No injuries were reported because of the failures.

“We have roughly 10,000 wind turbines in our fleet (roughly 30,000 blades). So in the context of our fleet, the number of issues we have is quite small,” Stengel said in an email.

Most recently a blade on a 160-foot turbine in rural Saginaw County, Michigan, snapped and was left dangling from its rotor Monday. It’s one of 75 turbines at the 120-megawatt Tuscola Bay Wind Energy Center, which is capable of powering 50,000 homes and began commercial operation in 2012.

In Nebraska earlier this month, one of 44 turbines at the Steele Flats wind farm in Gage and Jefferson counties crumpled in a corn field four miles south of Diller. The 1.7-megawatt turbine previously stood 262 feet tall at the hub and 422 feet at the tip of its blades. That facility went online in October 2013.

On June 5, a 2.5-MW turbine in northwest Iowa near Harris burst into flames and a blade plummeted to the ground.

NextEra says the fire began in the tower’s nacelle, which houses the generator, gearbox and brakes. It was part of the Endeavor I Wind Energy Center in Osceola County, which began operating in 2008.

Only a few days earlier, on May 31, a blade fell from its hub about 10 miles northeast of Enid, Oklahoma, at the 98-Megawatt Breckinridge Wind Energy Center, which was originally developed by Tradewind Energy and was later sold to NextEra.

Stengel said NextEra runs machines manufactured by General Electric at the Tuscola Bay, Breckinridge and Steele Flats wind farms. Cedar Rapids-based Clipper is the manufacturer of turbines at the Endeavor site.

A third-party contractor builds the turbines overseen by NextEra employees. The turbines are inspected and certified by the original manufacturer to be built to design specifications before beginning commercial operation, Stengel said.

While failures often get widely reported in media simply because of the high visibility of turbines, the percentage of structures that break is low.

GCube Insurance Services, Inc., based in California, released a 2015 study that showed 3,800 turbine blades fail across the globe annually, which was about half a percent of the 700,000 blades in operation worldwide at that time.

There currently are about 53,000 turbines in the United States, said Evan Vaughan, a spokesman for the American Wind Energy Association.

“Wind turbines consist of rugged but also sophisticated equipment, and operate under high wind conditions, subject to constant motion and sometimes challenging environments. Given these challenging operating conditions, wind turbines are remarkably reliable,” Vaughan said in an email.