Shipping of major items from their manufacturing ports to the construction ports. These include nacelles, blades, towers, floating substructures (either complete or as major sections), moorings, anchors, cables and offshore substations.

What it costs

About £3.9 million for a 450 MW floating offshore wind farm.

Who supplies them

Blue Water Shipping, Bourbon, Boskalis, Cadeler, Coordinadora Internacional De Cargas, DEME, Jumbo Shipping, Roll Group, SAL Heavylift, Saipem, Seaway 7, TechnipFMC, and United Wind Logistics.

Key facts

Turbine components are brought from several manufacturing locations to the construction port. Turbine suppliers operate dedicated transport vessels. These vessels are becoming increasingly specialised as blades and nacelles increase in size and mass.

Load-in operations depend on the component and the transport vessel type. Turbine suppliers and subsidiary manufacturers often use roll-on roll-off (ro-ro) vessels to minimise crane lifts during load-in. SPMTs are often used to transport components to the quayside and are sometimes used to move them onto vessels. Alternatively, land-based cranes may be used, or some vessels have their own cranes (see I.5.1 for further information).

Complete floating substructures are transported to the construction port either by towing with AHVs or on floating semi-submersible cargo vessels.

  • For towing, a minimum of two AHVs are required, and towing can only commence if there is an accessible port in case of an emergency within the shipping weather window.
  • Semi-submersible vessels can reduce the overall transit time but require careful load-out at the assembly port and load-off by submerging the delivery vessel at the construction port, where sufficient depth of around 20 m is required. As production rates increase it is expected that steel semi-submersibles will be shipped in sections for assembly at the construction port, due to their large footprints. It is expected that concrete semi-submersibles will be manufactured close to the construction port as their high mass will increase the cost of shipping.
  • Harbour tugs or small AHVs position the floating substructure in the wet storage area and hook-up to pre-laid mooring spreads. Alternatively, the floating substructure is moved directly to the quayside in preparation for final assembly.

Floating substructures can also be transported to the construction port in sections or components, where final assembly takes place (see I.5 for further information).

Other components that are too large for transport by road and rail use barges, ro-ro vessels or cargo vessels. The choice is driven by the size of the load and the sea conditions expected. These include parts for the anchor and mooring system, the dynamic array cable system, and items that might be pre-assembled into the floating substructure such as secondary steel, transformers, and circuit breakers.

  • Barges are suited to inshore shipping and calmer offshore waters but have relatively small capacities.
  • Ro-ro vessels have short turnaround times and may be used in more challenging seas. Some are specifically designed to suit particular wind turbine suppliers’ needs.
  • Cargo vessels are generally larger, with higher capacities, and are used for deep-sea shipping. Sea fastenings need to be stronger for rougher seas.

Transport, ro-ro and lifting operations are overseen by turbine supplier representatives, vessel crew and port stevedores to guard against damage.

What’s in it

Guide to a Floating Offshore Wind Farm