Flexibility keeps crews on schedule -- Offshore at Utgrunden

With the seventh and final rotor installed and last length of sea cable connected, offshore construction crews finished work last month on construction of the 10 MW Utgrunden wind farm near the south-eastern shores of Sweden.

The seven 1.5 MW turbines from the German facility of Enron Wind Corp of the US, previously marketed under the Tacke name, have been erected in a row in the middle of the Kalmar Strait, eight kilometres from the southern tip of Öland island and 12 kilometres from the mainland. The depth at Utgrunden is six to ten metres.

The crews kept within the time schedule despite a few unexpected problems. "We hit some big rocks when we were driving a pile," reports Mikael Jakobssen of Enron. "We didn't know whether we should just try to drive through them or remove them with dynamite, but we were able to drive through. One pile went down too smoothly, which worried us, but it turned out to be okay."

high winds

Timing the construction work around the vagaries of weather patterns is all part of the offshore learning curve for the construction team. "One of the things you find out on the water is that you have to be more flexible and have more options," continues Jakobssen. "If there are high winds, you skip a step and come back to it later. We were able to do tower sections and the nacelle, for instance, but then we would just wait with the rotors."

The Utgrunden project, which was awarded a standard capital subsidy of its eligible cost under Sweden's established wind program, in this case amounting to SKK 26 million, costs about SKK 180 million. "Based on our experience this time, we expect a lot more savings in the future," Jakobssen says. Enron hopes to commission the wind plant next month. It is expected to produce 38,000 MWh/year, covering the electricity needs of about 6000 homes.