Function
Offshore logistics involves coordination and support of offshore installation and commissioning activities.
Who is involved
High-level coordination is typically undertaken by the developer. Construction management services are conducted by specialist suppliers contracted by the developer.
Key facts
Offshore logistics covers all the work needed to ensure that construction proceeds smoothly, safely and on time.
Construction management covers a wide range of services including contract management, health and safety and marine coordination. In many cases, contractors are embedded in the construction management team.
Specialist software tools are available to plan and monitor offshore activity.
Weather and metocean forecasting services provide visibility of weather windows a few days in advance. Meteorological buoys are typically owned and operated in Ireland by the Met Éireann, third-party providers with their own forecasting algorithms.
Support vessels include guard vessels (potentially drawn from local fishing fleets), crew transfer vessels and accommodation vessels. These vessels may be contracted by the developer of the marine contractor.
Notable differences for floating
The construction port is where the floating substructure and the turbine are assembled. Inbound components are also marshalled and stored. Wet storage areas are required for the marshalling of floating substructures and for marshalling of assembled floating offshore wind turbines.
Construction port requirements for a 1 GW project are typically:
- Minimum of 20 ha suitable for lay down and pre-assembly of turbines
- Minimum of 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.
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.
