The installation of monopiles at the Arkona offshore wind farm site has been completed ahead of schedule with the last of the total of 60 monopiles now in place, allowing for an early start of the installation of the transition pieces.
All the transition pieces are expected to be installed by the beginning of next year.
In the spring of 2018, the offshore transformer station built in cooperation with the grid operator 50Hertz will be transported to the Arkona construction site and installed.
The 1,200t monopiles have been driven up to 40 meters deep into the seabed and E.ON, the project developer, said the short installation time of about two and a half months is exceptional, given that the seabed of the Baltic Sea is considered to be particularly challenging due to the heterogeneous subsoil and the possible occurrence of boulders.
A three-dimensional seismic investigation of the subsoil prior to installation provided important data on the sediment structure of the individual foundation sites in the connection with boreholes, which was used for the first time in Germany, E.ON pointed out. The locations were positioned on this basis, also to simplify installation and avoid the use of a drilling rig. The design of the steel foundations was then individually adapted to the soil conditions, the developer explained.
The monopiles, manufactured by EEW SPC and installed by Van Oord's heavy lift installation vessel Svanen, are 81 meters long and have a diameter of up to 7.75 meters. Bladt Industries has been in charge of manufacturing the transition pieces, and delivered the first batch to the Mukran Port in August.
The 385MW Arkona wind farm, a joint venture between E.ON and Statoil, is located 35 kilometres north-east of the German island of Rügen in the Baltic Sea, in water depths of 23 to 37 metres.
The wind farm will comprise 60 Siemens 6MW turbines, which A2SEA will start installing in 2018. It is scheduled for commissioning in 2019.