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Ship launched by Jan De Nul expands the scale of submarine cable installation and shows how giant structures are becoming part of the expansion of offshore wind energy in deep ocean areas.
Jan De Nul launched the William Thomson, the second ship of a pair designed to install submarine cables in shallow and ultra-deep waters, with operation planned up to 4,000 meters below the surface.
With 215 meters in length and capacity to transport 28 thousand tons of cables, the vessel is part of a new generation of maritime infrastructure aimed at expanding offshore electrical networks, especially in projects related to wind energy at sea.
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The ship is a twin of the Fleeming Jenkin, launched in October 2025.
According to the Belgian company, the two are among the largest of their kind ever built.
The function of these vessels is to transport long cables, reduce the number of joints on the seabed, and decrease the need for frequent returns to ports for reloading.
In practice, these ships operate as specialized platforms for storing and launching submarine cables.
Instead of transporting conventional cargo, they carry high-voltage structures that are unrolled over the ocean floor to connect wind farms, energy islands, and electrical networks on the mainland.
Submarine cables and offshore energy
The installation of submarine cables has become a significant role in the expansion of energy generation at sea.
Offshore wind turbines can produce large volumes of electricity, but this energy depends on transmission systems capable of bringing it to national grids.
In this context, ships like the William Thomson come into play.
The vessel was designed to accommodate long sections of cables in a single piece, which reduces the number of underwater connections.
Each fewer joint can represent less technical risk, less operation time, and, according to Jan De Nul, better installation quality.
The ability to work up to 4,000 meters deep extends the operational reach to areas beyond coastal regions.
In these zones, pressure, uneven terrain, and distance from the coast make cable installation an activity that requires technical planning, specific equipment, and constant operation control.
Besides the physical dimensions, there is a logistical change.
In projects with lower load capacity, vessels need to return more often to load new sections of cables.
With 28 thousand tons of capacity, Jan De Nul’s pair can cover greater distances before interrupting the service, which, according to the company, reduces costs and decreases the environmental footprint associated with the operation.
How Giant Ships Carry Energy Across the Sea Floor
Submarine cables are an essential part of offshore electrical infrastructure.
They transport energy generated at sea, connect conversion platforms, and enable different national systems to strengthen their networks.
The first major task planned for the ships will be in the 2 GW TenneT program, the network operator for the Netherlands and much of Germany.
The project envisions a new generation of connections for offshore wind farms, each capable of carrying up to two gigawatts.
This volume surpasses the current connections mentioned in the program, which typically range between 700 and 900 megawatts.
Jan De Nul itself compares the scale to an average nuclear power plant, which usually generates between 1 and 1.6 gigawatts.
The reference helps to size the expected capacity for a single offshore connection of two gigawatts.
For this program, Fleeming Jenkin and William Thomson are expected to install more than 2,800 kilometers of 525 kV direct current cables, distributed across four different connections.
This type of technology is used over long distances as it allows the transport of large blocks of energy.
The Fleeming Jenkin is scheduled for delivery in the last quarter of 2026.
The William Thomson is expected to start operations in the first half of 2027, according to the schedule released by the company.
Naval Technology for Ocean Energy Transmission
The construction of ships of this size highlights the scale of the works necessary for offshore energy transmission.
While wind turbines are part of the generation, submarine cables are responsible for bringing electricity to land systems.
The director of submarine cables in the offshore energy area of Jan De Nul, Wouter Vermeersch, stated that the William Thomson and the Fleeming Jenkin bring together the company’s accumulated experience in cable installation over the last 15 years.
According to him, the two ships are the most efficient and highest performing in the market.
The statement refers to the combination of load capacity, installation systems, and the company’s technical experience in this segment.
For Jan De Nul, the expansion of the fleet accompanies the demand for electrical infrastructure at sea, driven by the growth of offshore wind projects.
Another project mentioned for the fleet involves the Princess Elisabeth Island, an artificial energy island in Belgium.
In 2028, Jan De Nul intends to use one of the new ships to install three alternating current cables that will connect the island to the coast.
The structure will gather cables from the second Belgian offshore wind zone, called Princess Elisabeth Zone, and strengthen the interconnection between North Sea countries.
The project is conducted in partnership with the network operator Elia.
Installation of cables at 4,000 meters depth
Installing submarine cables requires more than just laying them on the seabed.
The operation involves tension control, precise positioning, and route planning so that the structure follows the underwater terrain without suffering deformations or damage.
In deep areas, operational conditions become more demanding.
The pressure increases as the depth advances, and failures during installation can compromise sections of high technical and financial value.
Therefore, specialized ships combine storage systems, launching equipment, and navigation technologies to keep the procedure within the parameters defined in the project.
The scale of the William Thomson also shows the physical dimension of modern energy infrastructure.
With 215 meters, the ship has a length greater than many tall buildings when compared horizontally.
Even so, its activity depends on controlled displacement, continuous monitoring, and precision in cable release.
From a technological point of view, the project illustrates how the seabed has become part of electrical transmission networks.
The energy generated by offshore winds can travel long distances through cables installed in regions of low light, high pressure, and difficult access.
The expansion of this type of infrastructure accompanies changes in the energy planning of coastal countries.
Electrical networks are beginning to include maritime structures, artificial islands, converter platforms, and high-voltage cables installed under the ocean.
The William Thomson is not yet in commercial operation, but its launch represents a step in the schedule for expanding Jan De Nul’s fleet for offshore transmission projects.
When it starts working, the vessel will be involved in projects connecting wind farms, energy islands, and onshore electrical networks.
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