The cable-laying vessel (CLV) lays the cables between the floating offshore wind turbines and offshore substation, and between the offshore substation and the onshore transition joint pit at cable landfall.

What it costs

This is included in the offshore cable installation contract.

A typical day rate for a CLV is about £150,000.

Who supplies them

Marine contractors: Boskalis, DEME, DeepOcean, Global Marine, Global Offshore, Jan de Nul, Oceanteam, Seaway 7 and Van Oord.

Cable manufacturers with installation capabilities: Nexans, NKT and Prysmian

Cable-laying vessel.
Cable-laying vessel. Image courtesy of Jan de Nul. All rights reserved.

Key facts

The same vessels may be used for export and array cable installation, although CLVs used to install export cables typically have larger carousels to accommodate longer cables. CLVs may need to have shallow drafts to install the export cables in shallow water close to shore.

Simultaneous lay and burial can be carried out with a variety of burial tools. In that case, the cable is buried during the lay to obtain immediate protection. Otherwise, a post-lay burial is required.

CLVs are characterised as follows:

  • Up to 30 m (breadth) by 140 m (length) and can operate at a speed up to 14 kn (transit speed).
  • Accommodation for a crew of up to 90.
  • The current capacity of carousels is of up to 10,000 t. Some contractors offer vessels with a double carousel which can increase carrying capacity (for example Jan de Nul’s Isaac Newton).
  • Likely to be equipped with a 3D motion compensated crane with up to 25 t capacity and a 25 t A-frame.
  • Generally equipped with a motion-compensated personnel transfer gangway and a helideck.

What’s in it

Guide to a Floating Offshore Wind Farm