Basin Electric repairs wind turbine blade

A major blade repair was completed this year at one of Basin Electric's wind projects.

The cooperative performs annual blade maintenance and repairs on its wind turbine generators (WTG) at its PrairieWinds 1 near Minot, North Dakota, and Crow Lake Wind near White Lake, South Dakota, locations.

In total, the electric cooperative owns and operates 188 WTGs at the two facilities - 80 at the PrairieWinds 1 site, and 108 at its Crow Lake facility. On average, about 10 minor blade repairs occur every year, said Joe Fiedler, manager of distributed generation, but this past spring a major repair was needed on one blade at PrairieWinds 1 after it was damaged by lightning.

"Previous blade repairs were performed while the blade was still attached to the hub of the WTG," he said. "This time the blade was removed and lowered to the ground for major rebuild."

Cranes and heavy rigging are used to remove the 122-foot-long blades, which are made of fiberglass cloth with a resin glue. They weigh roughly 7 tons and are attached to towers nearly 300 feet tall.

The first steps in repairing a blade involve prepping and cleaning the damaged area, followed by gluing layers of fiberglass cloth into place with the resin. "The major repair this spring involved removing the outer skin on one side down to the inner frame and completely rebuilding the skin layer," Fiedler said.

The wind projects were put into commercial operation in 2010 and 2011, respectively, Fiedler said. Lightning strikes, wind erosion, and hail are the typical causes for repairs.

He said it took about a month to complete the major blade repair this spring.