Offshore wind, transmission systems, driving demand for cable-lay vessels

Compared with NKT Victoria, the company’s existing cable-lay vessel, NKT Eleonora is huge. It will have a cable-laying capacity of 23,000 tonnes, advanced dynamic positioning system and technology that enables simultaneous installation of multiple power cables.

A highly advanced vessel in its own right, NKT Victoria – which entered service as recently as 2017 – is equipped for simultaneous laying of dual HVDC and fibre-optic cables, as well as HVAC and deepsea installations, but the twin turntables with which it is equipped have a combined capacity of just 11,000 tonnes.

Due to start work in 2027, NKT Eleonora is designed to operate on HVO/marine diesel oil, but the vessel is also one of the first cable-lay vessels in the world that will also be able to operate on methanol, in order to reduce its carbon footprint. It will have three turntables, and will be an environmentally friendly design with an Onboard DC Grid power system and a shore-power connection that will enable it to operate in ‘zero emissions’ mode when loading cable at NKT’s cable manufacturing facility in Karlskrona. The innovative vessel will be capable of laying three power cables simultaneously, responding to evolving customer requirements, especially on large-scale 525-kV projects, where metallic return cables (dedicated electrical conductors used in HVDC power transmission systems) are required.

Driven in large part by the rapid expansion of the offshore wind industry, the market for high-voltage subsea power cables has grown significantly in recent years and, as NKT noted when it ordered its new vessel, the outlook remains promising. At the same time, driven by the transition to renewable energy and electrification, transmission lines for offshore windfarms and for interconnectors are getting longer, creating new challenges for cable-lay vessels. Hence the large size of NKT Eleonora compared to NKT Victoria, and the significantly increased cable-carrying capacity of many other cable-lay vessels now on order: Jan De Nul’s newbuild cable-lay vessels Fleeming Jenkin and William Thomson, which will be the largest in the world, have a cable-carrying capacity of 29,000 tonnes. Boskalis’ new cable-lay vessel will have a cable carrying capacity of 24,000 tonnes on two 12,000-tonne carousels, including a concentric carousel that will enable the installation of longer continuous cable sections in a single uninterrupted operation.