The cylindrical piles are between 31 and 44 metres long and have a diameter of 1.80 metres and will be driven into the seabed up to a depth of 42 metres using a hydraulic hammer and a template. Belgian specialist company Geosea are carrying out the pile driving and are using the “Buzzard”, a jack-up barge, for the work.
“The Buzzard has been proved in several offshore construction projects as in during the erecting of the Belgian wind park Thornton Bank”, explained Hergen Stolle, head of alpha ventus offshore logistics and Vattenfall Europe’s project leader for the foundation and erecting work. “In Geosea, we have an experienced partner on board as specialists in offshore construction projects. I am confident that we can bring the work forward in good time”, Stolle added.
In addition, the pontoon vessel, Stemat 82, laid the first cables between the tripods and the already erected offshore transformer station. These “Innerpark” cables will later connect the wind turbines with the offshore transformer station which then transmits the wind power to the onshore networks.
The steel foundations, on which the REpower 5M wind turbines will stand, are called “Jacket” foundations. These lattice-tower constructions are presently being produced in
The second of two milestones this month
This month the alpha ventus project, a joint venture between EWE, E.ON and Vattenfall, has already marked a milestone in construction work. On 1 June, the last of the foundations for the other six turbines (AREVA Multibrid M5000) making up the wind farm was anchored successfully in the seabed and now six giant “tripods” rise out of the sea. The AREVA Multibrid team of approximately 70 in charge of installing the six huge structures (each weighing over 700t) have worked off the Odin, a jack-up barge necessary for driving the piles and assembling the wind turbines. The foundations comprising four supporting columns and standing firmly on the seabed protrude some metres above the surface of the sea to accommodate the equipment for construction work such as vibrators, under-water hammers, diving station, workshop and office container etc. Odin will be replaced by the larger jack-up barge JB-114 for the subsequent installation of the wind turbines.
Construction of the twelve wind turbines is planned to be completed by the end of 2009, when the six Areva Multibrid M5000 and six REpower 5M turbines will be started up to supply environmentally friendly power equivalent to the consumption of 50,000 households. “The construction of the wind farm is currently making good progress and is making a valuable contribution to our learning curve”, explains Wilfried Hube, overall project leader of alpha ventus.
Ongoing activities at the offshore construction site can be monitored over the Internet, as a webcam positioned on the FINO1 research platform is directed at the construction site and provides up-to-the-minute pictures.
