O.3.2 Main component refurbishment, replacement, and repair (tow-to-port)

Who supplies them

AHVs: Boskalis, Bourbon Offshore, Damen, DOF Subsea, Maersk, MMA Offshore, Siem Offshore, SEACOR Marine, Solstaad Offshore and Vard Marine.

Construction ports in the UK: Aberdeen, Cromarty Firth and Dundee.

Jack-up cranes: DEME, Fred. Olsen, Jan de Nul, Seajacks, Seaway 7, and Van Oord.

Key facts

Conducting main component refurbishment, replacement and repair in-situ is challenging as motion-compensated lifting operations are required. Alternatively, floating offshore wind turbines can be towed to port for main component refurbishment, replacement, and repair to take place.

This involves disconnecting the floating offshore wind turbine from its moorings and cables and towing it to a port using AHVs. At the port, maintenance work can be undertaken using a jack-up vessel or a large land-based crane.

A tow-to-port strategy is less attractive than an in-situ strategy because turbine downtime is longer, resulting in larger revenue losses. It also requires floating offshore wind turbines to be towed to a construction port with the space, facilities and water depth required to repair floating offshore wind turbines. Alternatively, the floating offshore wind turbine could be towed to a sufficiently shallow, sheltered site where a jack-up crane vessel would be used.

Tow-to-port also requires floating offshore wind turbines to be disconnected and reconnected from cables and moorings.

Due to the unavailability of in-situ main component refurbishment, replacement, and repair, this is the only option currently available to floating offshore wind farm owners.

Retrofit programmes are carefully planned to ensure effective vessel utilisation, taking into account repair turnaround times. This means that asset downtime, and hence lost revenue, is minimised.

What’s in it

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• I.4.1. Anchor-handling vessel
• I.8. Construction port
• Jack-up vessel or land-based crane