Stillstrom by Maersk has completed the construction and factory acceptance testing of a vessel-mounted unit designed to enable service operation vessels (SOVs) to charge their batteries directly from offshore wind farms.
The Vessel Container Unit (VCU) houses the 11 kV connection equipment that links a vessel to the offshore charging infrastructure. Its modular design allows it to be installed at the bow, stern or under the deck, and integrated into both newbuild and existing vessels. The unit can also be transferred between vessels where the necessary onboard cabling is available.
The factory acceptance testing was witnessed by DNV. Stillstrom said the VCU’s integrated connection and control systems are designed to manage charging and disconnection while allowing vessels to maintain their position offshore.
The company said the milestone covers the vessel-side connection equipment, while work on the offshore infrastructure that will supply power to vessels is continuing, with the complete charging system expected to be ready for extended offshore trials by summer 2027, as the interface on the wind farm side progresses towards completion by the middle of next year.
Stillstrom has been developing offshore charging technology for service vessels since 2019. In August 2026, the company completed a trial of its automated cable control system with Esvagt and Semco Maritime, demonstrating how the charging cable can be deployed and retrieved while a vessel maintains position using dynamic positioning.
In September, Stillstrom signed a letter of intent with Semco Maritime for the manufacture and delivery of a local equipment room (LER), which will house the transformer, medium-voltage switchgear and other systems needed to transfer power from an offshore wind farm to a vessel. Production of the first unit is planned at Semco Maritime’s facility in Esbjerg, Denmark, with completion targeted for spring 2027.
The company is also developing a second-generation VCU, which is expected to move from the current semi-automatic alignment process towards full automation.
Stillstrom established a dedicated UK entity in Aberdeen in March 2026, when it said it was preparing for commercial deployment of its offshore charging technology in the UK market. The company has also been selected for support from the European Commission’s Innovation Fund for its OffshoreCharge project, which aims to install its first commercial 7.5 MVA offshore charging system for electric service operation vessels.