Offshore energy solutions company Jan De Nul has launched a new next-level high-performance vessel: the William Thomson, one of two identical subsea cable‑laying vessels currently under construction.

Both vessels have a cargo capacity of 28,000 tons and a length of 215 meters. “This makes them the largest, most efficient, and highest-performing cable-laying vessels of their kind,” Wouter Vermeersch, Director Subsea Cables Offshore Energy at Jan De Nul said.

Reducing costs

The two new vessels have been specially built to install cables, both in shallow and ultra-deep waters down to 4,000 meters. Thanks to their large loading capacity, they can take longer cables on board in a single piece and bridge longer distances with as few subsea cable connections as possible.

Compared to similar ships on the market, they require fewer return trips to load cables, reducing costs, minimizing the environmental footprint, and enhancing cable quality.

First assignment

Sister vessel Fleeming Jenkin was launched in October 2025, with delivery scheduled for the last quarter of 2026. The William Thomson will follow shortly and will be operational in the first half of 2027.

Once operational, both ships can immediately get to work on their first assignments. Their first project is the 2GW program by TenneT, the grid operator for the Netherlands and large parts of Germany. These ships will likely be fully booked years in advance.

Offshore energy solutions

This introduces a new generation of grid connections for offshore wind farms, each capable of transporting up to two gigawatts. That is more than double the capacity of current connections. For this project, both ships will install more than 2,800 kilometers of 525 kV DC cables for four different grid connections.

In 2028, Jan De Nul will also deploy one of these new vessels to install three 220 kV AC cables connecting the Princess Elisabeth Island to shore. This energy island, which Jan De Nul is building in a joint venture for grid operator Elia, will bundle cables from Belgium’s second offshore wind zone (Princess Elisabeth Zone) and strengthen interconnection between the North Sea countries.

Strategically important

Jan De Nul is investing heavily in expanding its existing subsea cable capacity.In addition to the two cable-laying vessels, three more ships will be added to protect them.

Historically, Jan De Nul was known for dredging activities and land reclamation, but over the last 15 years, they’ve built a serious offshore energy division. These two cable-laying vessels massively upscale capacity.

Wind farms are being built fast, but connecting them to shore is becoming the limiting factor. That is why the new ships are strategically so important. They are more reliable, cost-effective, and capable of handling larger projects.

Today, Jan De Nul operates roughly 80 to 90 vessels, including dredgers (core business), offshore installation vessels, cable-layers, and support vessels.