I.1.1 Foundation installation vessel

Function

The foundation installation vessel transports the foundations from the quayside fabrication facility or construction port [I.7] to the site and secures them to the sea bed. Heavy lift vessels, floating sheerleg vessels and self-propelled jack-up vessels are all used.

What it costs*

These costs are typically included in the foundation installation contract. A monopile installation vessel for a 1 GW wind farm will cost around £75 million. A TP installation vessel for a 1 GW wind farm costs around £41 million.

Who supplies them

Operators: Boskalis, Fred. Olsen WindCarrier, GeoSea (DEME Group), Jan de Nul, Jumbo Offshore, SAL Heavy Lift, Saipem, Scaldis Salvage & Marine, SeaJacks, Seaway Heavy Lifting (Subsea 7 Group), Swire Blue Ocean and Van Oord Offshore Wind. 

Vessel manufacturers: as for Turbine installation vessel [I.6.1].

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Key facts

Foundation installation vessel fleets have overlapped with turbine installation fleets in the past but these are diverging due to the increasing size and mass of components and the relative merits of jack-ups and floating heavy lift vessels.

Foundation installation has made considerable use of vessels originally built for other sectors, including oil and gas, bridge building and near-shore construction.

With the mass of monopiles increasingly exceeding 1,000 t, few jack-up vessels have the necessary lifting capacity. With the jacking process lasting several hours and the lower weather sensitivity of the installation process (compared with turbine installation), a floating installation vessel has notable advantages. Disadvantages have been the relatively high charter rates and low availability of heavy lift vessels with a maximum crane capacity of 1,500 t or greater. The recent investments in heavy lift vessels for the offshore wind market by Boskalis and GeoSea are considerable. A typical specification for a latest generation heavy lift vessel is:

• Length: 260 m, beam: 50 m, draft: 12 m
• Crew berths: 150
• Crane: 2,000 t
• Maximum transit speed: 14 knots
• Component capacity: Up to 7 foundations, and
• Dynamic positioning system.

Jacket foundations are typically lighter than monopiles for equivalent depths and the choice of vessel is driven by a number of factors including deck space and lift capacity. Installation using jack-ups is affected in particular because the position of the legs limits the flexible use of deck space. One of the advantages of three-legged jackets is that they enable better use of deck space.