The Arkona offshore wind project is growing significantly faster than expected. All 60 foundations have been installed in the seabed of the Baltic Sea ahead of schedule. The short installation time of about two and a half months is exceptional, as the sea bed of the Baltic Sea is considered to be particularly challenging due to the heterogeneous subsoil and the possible occurrence of boulders. The monopiles, which weigh around 1,200 tons, were tied up to 40 meters deep into the seabed.
One success factor was the three-dimensional seismic investigation of the subsoil prior to installation. It 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. 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 foundations are 81 meters long and have a diameter of up to 7.75 meters.
At the same time, the Arkona project was the first company in the offshore industry to develop and implement an innovative technology for corrosion protection of steel foundations with the monopile installation. A new coating process significantly reduces the environmental impact during operation compared to the conventional method. E. ON applied for the German Renewables Award with this procedure.
The rapid construction progress allows an early start of the assembly of the transition pieces. This work is to be completed 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 Arkona project is located 35 kilometres northeast of the island of Rügen. The wind farm will have a capacity of 385 megawatts (MW) and will be able to supply up to 400,000 households with renewable energy from 2019 onwards. Compared to conventionally generated electricity, Arkona saves up to 1.2 million tons of CO2 per year. The installation includes 60 six-megawatt class turbines from Siemens. The plants are based on monopile foundations at water depths of 23 to 37 metres. Arkona is a joint venture between E. ON and the Norwegian energy company Statoil.