Plugging Ships Into Wind Turbines: Stillstrom Tests 11 kV Offshore Vessel Charging Unit

Every day, crews on service ships help keep offshore wind farms running. They spend days living on board, crossing over to turbines to fix, inspect, and maintain them. It's ironic that most of these ships burn fuel while sitting next to huge electricity generators at sea. Stillstrom wants to change that by plugging them in.

Stillstrom by Maersk has finished building and testing its Vessel Connection Unit, or VCU.^[1] Factory acceptance testing means running all the checks before a machine leaves the workshop, and DNV, an independent certification body, watched the process.^[2] The company says this is the world's first 11 kV interface unit for charging vessels at offshore wind farms.^[1]

How offshore vessel charging works

The VCU is placed in a shipping container on the ship's deck. Inside, it holds the 11 kV connector package.^[3] It pulls in a high-voltage cable from the turbine and locks it in place, letting a service vessel charge its batteries straight from the wind farm.^[4][5] Since it's self-contained, the unit can be added to new ships, retrofitted to older ones, or even moved between ships with the right cabling.^[6][7]

This is important because, according to the company, high-voltage power has never been transferred to a vessel offshore like this before.^[8] The challenge isn't the electricity itself. It's making a safe, watertight, high-voltage connection on a moving ship, and then disconnecting it smoothly when finished.

The project has strong ties to Scotland. Stillstrom started in 2019 as a Maersk innovation project, became an independent company in 2022, and set up a UK branch in Aberdeen in March 2026.^[9][10] Graeme Wood, Managing Director of Stillstrom UK, summed it up: “In simple terms, the VCU has been built and tested, and we are good to go.”^[11]

The next step is to test the system at sea. The company expects its full charging system to be ready for longer offshore trials by summer 2027.^[12] You can find more details in Stillstrom's announcement and Offshore Wind's report. For more about the cables bringing wind power ashore, check out our story on the 95 subsea cables at East Anglia THREE.

What happens next

Testing in the factory is one thing, but the North Sea is a different challenge. Sea trials will have to prove the connection is safe in wind, waves, and salt spray, that crews can connect and disconnect it quickly, and that turbines can supply the power without affecting the grid. Standards and certification for charging at sea are still being developed along with the hardware.

What this means for you

Behind this are electrical engineers who design high-voltage connectors and protection systems, marine engineers who fit the equipment into working vessels, and offshore wind technicians who keep the turbines running. Many of these jobs are based in UK ports such as Aberdeen, where Stillstrom has its UK company. Our guide to starting a career in electrical engineering explains the subjects and qualifications you need, and our beginner’s guide to finding an engineering apprenticeship shows how to earn while you train.