Two Offshore Substations Sail from Dutch Yards for German Baltic Sea Grid Project

The topsides and jackets for the OSS Zingst and OSS Darß offshore substations have left the Netherlands, bound for the German Baltic Sea, where they will be installed as part of the OST-6-1 offshore grid connection being delivered for transmission system operator 50Hertz.

The HSI Joint Venture, which built the structures, describes the departures as a major sail-away milestone in the delivery of the connection, which will link the Gennaker Offshore Wind Farm to the 50 Hertz transmission system on land.

Two Dutch yards, one destination

The structures were built and integrated across two Dutch locations. The topside and jacket for OSS Zingst departed from Schiedam, while the equivalent structures for OSS Darß sailed from Vlissingen. With both sets of substations now under way, the project moves from engineering, construction, and integration into transport, offshore installation, and commissioning in the German Baltic Sea.

The sail-aways followed an extensive period of engineering, procurement, fabrication, assembly, and integration carried out across the two yards. Each offshore substation has a capacity of approximately 450 MW.

Connecting Gennaker to the Onshore Grid

Once installed, OSS Zingst and OSS Darß will transmit power from the 927 MW Gennaker Offshore Wind Farm in the German Baltic Sea towards the onshore grid connection. The project forms part of the continued expansion of offshore energy infrastructure in the German Baltic Sea.

The grid connection sits against a broader backdrop, as the JV partners see it. According to Smulders, offshore wind is one of the key pillars in Europe's changing energy system. As electricity demand grows and more industries, transport systems, and households move towards low-carbon power, large-scale renewable generation needs to be matched by reliable grid infrastructure.

Full EPCIC Scope Under the HSI Joint Venture

The HSI Joint Venture combines Smulders HSM and Iv. The partners hold responsibility for the complete EPCIC scope of the topsides and jackets for both offshore substations, covering engineering, procurement, construction, transport and installation, and commissioning. The company states that this integrated approach brings together offshore engineering expertise, steel fabrication, systems integration, and project execution within a single delivery team.

What the Teams Say

Hans Leerdam, Commercial Director at Smulders HSM, said the sail-away of OSS Zingst and OSS Darß is an important milestone for everyone involved. "Delivering two complete offshore substations of this scale requires close integration across engineering, procurement, fabrication, systems integration, and offshore execution. Seeing the topsides and jackets depart reflects the expertise, commitment, and collaboration of the teams within Smulders HSM and Iv, together with our client and project partners," he said.

Fedor van Veen, Managing Director Offshore & Energy at Iv, said the sailaways demonstrate what it takes to turn complex designs into reliable offshore infrastructure. "Constant alignment between design and construction, across multiple teams and locations. Bringing everything together at this scale is a strong achievement and a clear example of what European industrial cooperation can deliver," he said.