Figure 70 CTV during service operations, © MHI Vestas Offshore Wind.
Function
CTVs provide access for technicians and contractors to the wind turbines from the onshore OMS base to turbine locations and substation. CTVs are the preferred access solution for projects closer to shore.
What it costs*
The charter day rate for a CTV varies significantly depending on specification, availability and contract period.
Who supplies them
Vessel operators: Acta Marine Wind Services, BA Technologies, Mainstay Marine Solutions, MJ Power, MPI Workboats, Njord Offshore, Northern Offshore Services, North Sea Logistics, OEG Renewables, Seacat Services, Turbine Transfers and Windcat Workboats.
Manufacturers: Alicat, Fjellstrand, Fred. Olsen WindCarrier, Manor Renewables, South Boats and Umoe.
Key facts
CTVs transport personnel to the wind farm on a daily basis and do not have overnight facilities.
Key requirements are robust vessels that can operate in adverse weather conditions. Wind farm operators typically use aluminium catamarans up to 30 m long with capacity for 12 to 16 technicians.
CTVs are typically Class I passenger ships, as classified by the Maritime and Coastguard Agency, which enable them to work further than 60 nm from a safe haven. These vessels can be built to carry up to 24 passengers. Vessel speeds can be up to 30 kn and are designed to transfer maintenance and service team members in comfort and safety to the wind farm ready to start work.
There is an oversupply of small CTVs (less than 20 m), with operators typically opting for larger vessels with longer ranges and better sea keeping.
There is interest in SWATH (small waterplane area, twin hull) and SWASH (small waterplane area, single hull) type vessels to increase technician comfort and lower weather downtime.
Electric Crew Transfer Vessels are beginning to be used to reduce emissions, with companies retrofitting existing vessels and developing new electric fleets.
CTVs may have fixed or controlled pitch propellers but operators may prefer the increased manoeuvrability of water jets. Vessels with a smaller draught (less than 2 m) may be used where harbours are more challenging to operate from due to water depths.
CTVs have a load capacity up to 30t for turbine components and consumables, as equipment. Fuel is not typically included in the charter cost and there is an important emphasis on fuel efficiency of vessels.