A lateral crack three meters wide and 10 feet long on one of the blades was cause to shut down one of the turbines south of Fairmont.
The crack, believed to be a factory flaw, was found in mid-February. Around the same time, another smaller crack was discovered on the blade of a second turbine.
The repair job was delayed by a number of factors, but things should be getting on track soon – if the wind isn’t too strong for workers to do their job. Weather permitting, work on two of Fairmont’s four wind turbines was scheduled to start this week.
The rotor, which consists of three 131-foot long blades and the hub, weighs 43,000 pounds. Taking it down is no small task – two 300-ton capacity cranes are needed for the job. The cranes were held up by road construction. Then when the cranes finally arrived, no workers were available to fix the damaged blades, according to Tom Kueritz, public utilities director.
The cracks should be epoxied, and the rotor hoisted back in place in a matter of three weeks, Kueritz hopes.
“We’ve lost a lot of generation off those with the winds we’ve had,” Kueritz said.
Figuring out how much energy and dollars were lost during the past four months is difficult, according to Larry Johnston with Southern Minnesota Municipal Power Agency, the agency that owns the turbines.
“How many kilowatt hours we’ve lost in the production process – that’s really hard to get a handle on without going through each of the daily wind speeds and trying to come up with that and applying it to the power curve for those turbines,” Johnston said.
Johnston did make a very rough estimate of “4-5 million kilowatt hours that we’re probably missing during the down period of time.”
And time is money. While the repair work is under warranty through Vestas of Denmark, Johnston wasn’t certain if the company will reimburse SMMPA for the lost energy.
“We’re currently looking through our warranty and taking a look at how those things are impacted and trying to get our hands on those next steps to see what they are,” Johnston said.
“The most important thing to us of course is we’ve got cranes back on site and we can get them up and operating,” he added.
The two damaged 1.65 Megawatt turbines have been running since 2005. The other two turbines, on the west side of the highway, went up in 2003.
By Megan Feddersen
19 June 2007
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