Warren Buffett-owned Berkshire Hathaway subsidiary, MidAmerican Energy, has idled more than 40 wind turbines at Iowa wind farms after a 50 metre-long turbine blade broke off and fell into a field last week.
The Des Moines-based utility said on Tuesday that it had paused the use of 46 Vestas wind turbines to check them for safety, after a blade broke off a similar turbine in September, and another earlier this year, and one in 2019.
MidAmerican said the latest fallen blade was discovered by a technician at the Beaver Creek wind farm last Thursday, in a harvested field southeast of Paton in Greene County. It had broken somewhere along the blade’s length and not at the base, the company said.
This followed a similar incident in September at MidAmerican’s Arbor Hills wind farm in Adair County, where a turbine blade broke off a turbine and fell into a cornfield. And at the company’s Orient wind farm, also in Adair County, blades broke from turbines in April of this year and October 2019.
For Danish wind giant Vestas, it’s the second time this month that its name has been linked with a “blade detachment incident,” after a newly installed turbine at Australia’s Dundonnell wind farm, in Victoria, dropped a 73 metre, 70 tonne blade. Happily, no one has been injured in any of either the US or Australian incidents. But it’s not a good look.
As of last week, Tilt Renewables had not yet determined the cause of the Dundonnell incident, with 25 of the wind farm’s unaffected turbines cleared to resume production, and the remainder being returned to service “in a safe manner” after a run of inspections and tests.
In the case of the Iowa blade breaks, MidAmerican is looking into the turbines’ lightning channelling system – one of various in-built safety features of the Vestas turbines.
MidAmerican spokesman Geoff Greenwood told Radio Iowa that the company had singled out other turbines with the same system and made by Vestas – and which had also a lightning strike near them – for closer investigation.
“The turbine that had the blade failure last week is the same type of turbine that had a blade failure last month in Adair Countym” he said.
“They also had the same type of lightning system in them that channels lightning from a strike near a wind turbine blade down into the ground safely.
“So we have turned off those wind turbines while we methodically check those blades and the lightening systems in them to ensure that they are safe.”
Greenwood noted that, for a company with some 3,000 turbines in operation across Iowa, this was a rare issue – but added, “even once is one too many — and we want to do everything we can to make absolutely sure that these blades are safe.”
He said the team of technicians were limited in what they could do by certain weather conditions that prevented them from safely going up into the blade.
“There’s a certain threshold of wind — for example if the win exceeds a certain speed — they can’t go up that day,” Greenwood says. “So, we can’t say for sure that we can do it this day, this day and this day, because it is weather contingent.”
Greenwood says the turbines and blades are built to withstand the Iowa weather and they have controls that can adjust them to various wind speeds. He says they did not have any major problems with turbine damage when the derecho hit in August.