The construction port is where inbound components are marshalled and stored, the turbine is pre-assembled, and the turbine is finally assembled with the floating substructure. Wet storage areas are required for the marshalling of floating substructures and for marshalling of assembled floating offshore wind turbines. A construction port is one that is only used for marshalling components.

What it costs

This is included in installation contracts.

Who supplies them

Construction ports used for early pre-commercial floating projects: Aberdeen (UK), Cromarty Firth (UK), Dundee (UK), Ferrol (ES), Lorient (FR), Nouvelle (FR), Rotterdam (NL), Skipavik-Gulen (NO) and Stord (NO).

The Port of Cromarty Firth used as the construction port for the Kincardine project.
The Port of Cromarty Firth used as the construction port for the Kincardine project. Image courtesy of Port of Cromarty Firth. All rights reserved.

Key facts

Construction port requirements for a 450 MW project are typically:

  • Between 15 and 20 ha suitable for lay down and pre-assembly of turbines
  • Between 10 and 12 ha of wet storage for storing floating substructures prior to final assembly, and for storing assembled floating offshore wind turbines prior to tow-out
  • Quayside length of around 500 m with load bearing capacity ranging from 40 to 100 t/m2 and adjacent access
  • Quayside water depth of between 12 and 20 m to accommodate the draft of floating substructures and semi-submersible transport vessels
  • Water access to accommodate delivery vessels for floating substructures and turbine components. These are up to 160 m length, 45 m beam and 6 m draft with no tidal or other access restrictions
  • No air draft restrictions, to allow tow-out of assembled floating offshore wind turbines with tip heights of about 250 m, and
  • As close as possible to the installation site to minimise the time to tow-out and sensitivity to weather windows, although the distance depends on many factors including the location of ports relative to the site, the cost to upgrade ports (where necessary) and the cost of fuel.

Large areas of land are required due to the space taken when turbines are stored lying down on the ground.

Sites with greater weather restrictions or for larger scale construction may require an additional lay-down area of up to 30 ha.

Wet storage is required to temporarily store floating substructures delivered to the construction port before final assembly with the turbine at the quayside. This storage can also be used prior to tow-out of the assembled floating offshore wind turbines with seafaring AHVs.

Separate ports may be used to fulfil the functions of a construction port for the floating offshore wind turbine, the mooring system and the cable system.

Different construction ports may be used to feed floating substructures and wind turbines, separately, to a wind farm if new methods are introduced for final assembly of turbines directly onto moored floating substructures at site. This would require semi-submersible or capable monohull heavy lift vessels to install the turbine as site water depths are not suitable for jack-up installation vessels.

An alternative to using quayside final assembly of turbines and floating substructures is to assemble them in a dry dock, but there are few dry docks which have suitable width for a typical three-column semi-submersible.

What’s in it

Guide to a Floating Offshore Wind Farm