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Wind farm back with fix for fallen blade

A desert wind farm supplying electricity to San Diego is back online after the conclusion of a probe into a fallen turbine blade.

Turbine manufacturer Siemens found that the detachment of a 170-foot blade at the Ocotillo Wind power plant in May, along with a second blade at an Iowa wind farm April, were the result of insufficient adhesive bonding.

The company’s root cause analysis found that the separation happened where the fiberglass laminate of the blade meets a pre-cast blade “root,” adjacent to the turbines’ revolving hub, a spokeswoman for Siemens said.

Seven blades are being replaced at the Ocotillo plant as a result of the inquiry, according to Pattern Energy, the Bay Area-company that developed and operates the Ocotillo facility.

The blade failures have proven costly for Siemens.

On Wednesday, the Munich, Germany-based industrial conglomerate reported a charge against earnings of roughly $120 million at its wind power division related to inspecting and retrofitting turbine blades, mainly in the U.S.

The incidents in Iowa and California involved identical turbine and blade models. That blade – the B53 type – is used on about 700 units in operation worldwide – 600 of those the United States. The turbines were either idled or operated at limited speed while Siemens studied what went wrong.

In a statement, Siemens said that all wind turbines with B-53 blades have been inspected and the majority returned to operation, without providing specific numbers.

“Siemens will apply a minor modification in the field to all existing B53 blades worldwide that are not otherwise replaced,” the company said.

The fallen blade at Ocotillo, 70 miles east of the City of San Diego, has ignited safety concerns among critics of a turbine array that forms a crescent around the town of fewer than 300 residents.

The project, with more than 90 turbines, is located primarily on public land overseen by the Bureau of Land Management and remains accessible to hikers and some vehicles.