‘William Thomson’ is one of two identical cable-laying vessels currently under construction for Jan De Nul
Jan De Nul has announced the launch of its latest high-performance offshore installation vessel, William Thomson, further strengthening its capabilities in the rapidly growing subsea cable installation market.
The vessel forms part of a two-unit series of identical subsea cable-laying vessels under construction. Each vessel will measure 215 metres in length and offer a cable capacity of 28,000 tonnes, positioning them among the largest cable-layers in operation upon delivery.
Subsea cables are needed to bring energy generated at sea ashore and to connect the electricity grids between different countries and regions. This is essential for building a reliable energy network based on renewable sources, enabling electricity to flow easily from areas of surplus to areas of shortage.
Jan De Nul’s two new cable-laying vessels have been specially built to install these cables, both in shallow and ultra-deep waters down to 4,000 metres. 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 other cable-laying vessels on the market, they therefore also need to make fewer return trips to load cables. This reduces costs, minimises the environmental footprint and enhances cable quality.
Sister vessel Fleeming Jenkin was launched in October 2025 and her delivery is scheduled for the last quarter of 2026. The William Thomson will follow shortly and will be operational in the first half of 2027. Both vessels and the technologies on board have been designed by Jan De Nul’s in-house experts.
“The William Thomson and her identical sister, the Fleeming Jenkin, bring together all the expertise in cable installation that we have built up over the past fifteen years. They are the highest-performing and most efficient cable-laying vessels on the market.” – Wouter Vermeersch, Director Subsea Cables Offshore Energy at Jan De Nul
Once operational, the Fleeming Jenkin and William Thomson can immediately get to work on their first assignments.
Their first project is the 2GW programme by TenneT, the grid operator for the Netherlands and large parts of Germany. 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, which typically range between 700 and 900 megawatts, making offshore wind energy more efficient and affordable. By way of comparison, an average nuclear power station typically generates between 1 and 1.6 gigawatts.
For this programme, Fleeming Jenkin and William Thomson will install more than 2,800 kilometres of 525 kV DC cables for four different grid connections.
