Crane ship the Pioneering Spirit installed the OSS Zingst and OSS Darß offshore platforms in the Baltic Sea. Credit: 50Hertz/Tom Schünemann.

50Hertz has announced the successful installation of two offshore substations for the 976MW Gennaker offshore wind farm in the Baltic Sea, a significant step forward in the ongoing OST-6-1 grid connection project.

The platforms, named OSS Darß and OSS Zingst, were installed in coastal waters near the Fischland-Darß-Zingst peninsula.

They will form the central point of the Gennaker wind farm’s cable connections.

Heavy-lift vessel the Pioneering Spirit, which measures more than 380m, was used for the installation work.

Power cables from the development’s 63 wind turbines will converge at these platforms, where voltage will be stepped up from 66kV to 220kV before being transmitted to shore.

According to the project outline, three cable systems will carry electricity over a route totalling around 90km, with up to 53km of the line running under the Baltic Sea and 35km continuing on land to the new Gnewitz substation.

The grid connection system carries a transmission capacity of up to 927MW.

The Gennaker wind farm is being developed and operated by OWP Gennaker, a joint venture (JV) between Stadtwerke München and Skyborn Renewables.

It has the potential to supply electricity to around one million households.

The project is located approximately 15km north of the German coast within the Darß priority area.

Construction was completed in several phases. The foundation structures, called jackets, were initially placed on the seabed and secured using suction.

The substations’ upper sections, or topsides, each weighing several thousand tonnes, were then lifted onto the supports by the Pioneering Spirit’s cranes.

The topsides and jackets were produced at shipyards in Vlissingen and Rotterdam/Schiedam, the Netherlands, and transported to the installation site by tugboats.

The JV of Smulders, HSM Offshore Energy and Iv-Offshore & Energy was responsible for the design, construction, installation and commissioning of the platforms.

Allseas Engineering oversaw the offshore installation.

Commissioning of the wind farm and full grid connection is targeted for 2028.

Last month, Skyborn Renewables obtained more than $3.36bn (€3bn) in financing to support the Gennaker wind farm.