Stillstrom Completes 11 kV Unit for Offshore Wind Vessel Charging
Maersk-backed Stillstrom finishes testing modular charging unit for offshore wind service vessels.
1Modular Charging Unit Milestone
Stillstrom by Maersk has successfully completed factory acceptance testing for its 11 kV Vessel Container Unit. This modular hardware enables service operation vessels to charge batteries directly from offshore wind farm infrastructure. The unit is designed for flexible installation at the bow, stern, or under the deck of various maritime vessels.
2Technical Integration and Testing
The testing process for the container unit was officially witnessed by DNV to ensure compliance with safety standards. Integrated control systems manage the complex charging and disconnection procedures while vessels maintain their precise offshore positioning. This capability is essential for ensuring operational stability during the energy transfer process in challenging marine environments.
3Infrastructure Development Timeline
While the vessel-side connection equipment is ready, work continues on the offshore infrastructure required to supply power. The complete charging system is currently scheduled for extended offshore trials by summer 2027. Interface development on the wind farm side is expected to reach completion by the middle of next year, enabling future connectivity.
4Evolution of Charging Technology
Stillstrom has been actively developing offshore charging solutions since 2019. In August 2026, the company successfully trialed an automated cable control system alongside Esvagt and Semco Maritime. This demonstration proved that charging cables can be deployed and retrieved safely while vessels utilize dynamic positioning systems to remain stationary during the power transfer.
5Strategic Manufacturing Partnerships
In September, Stillstrom signed a letter of intent with Semco Maritime to manufacture a local equipment room. This facility will house critical transformers and medium-voltage switchgear necessary for power transfer. Production is planned at Semco Maritime’s facility in Esbjerg, Denmark, with the first unit completion targeted for the spring of 2027.
6Future Automation Roadmap
The company is currently developing a second-generation Vessel Container Unit to enhance operational efficiency. This iteration aims to transition from the current semi-automatic alignment process toward full automation. By reducing human intervention, Stillstrom intends to streamline the charging sequence and improve the overall reliability of power delivery for electric service operation vessels.
7Market Expansion and Funding
Stillstrom established a dedicated UK entity in Aberdeen in March 2026 to prepare for commercial deployment. The company also secured support from the European Commission’s Innovation Fund for its OffshoreCharge project. This initiative aims to install the first commercial 7.5 MVA offshore charging system, marking a significant step toward widespread industry adoption.
8Industry Impact and Outlook
The development of offshore charging infrastructure represents a critical shift toward decarbonizing the maritime support sector. By enabling electric service vessels to recharge at sea, operators can significantly reduce fuel consumption and emissions. Successful trials and infrastructure scaling remain the primary indicators for the commercial viability of this sustainable offshore energy technology.