According to one source, 25-30 E40 turbines have been hit by the problem, though Enercon's Aloys Wobben disputes this figure, believing it to be smaller. "This is not a big problem for the company," he stresses. Wobben says only older E40 models are affected and Enercon is paying for the necessary retrofit work. He says Enercon guarantees 97% availability of the machines, but none have been stopped for periods long enough to make Enercon liable for any financial loss from lack of production.
The operator of Bürger Windpark Lubke-Koog, Hans-Detlef Fedderson, says seven of his turbines stopped working after a storm on October 10. "This is not the first time the problem has occurred," says Fedderson. "It is a combination of the coastal location of our machines and the open construction of the generator." The result of the salt water contact on the windings is a short circuit in the pole shoes, he says. These were replaced by Enercon.
xWobben explains that on newer E40 turbines, protecting flaps and sealing brushes have been mounted between the rotor and the generating housing to prevent water getting into the generator housing.
Another operator, who declines to be named, also says the problem occurs only at coastal areas. He blames the use of poor quality paint on the generator, which allows salt water to seep through. He also says the paint cannot withstand the extremes of temperature to which wind turbines are subjected. Wobben admits that the resin used for the early generators did not live up to the manufacturer's claims. "The resin did not get really hard," he adds. It is no longer used by Enercon. All the affected wind turbines have been repaired on site and none of the repairs required major replacement of parts, stresses Wobben.