The forecasted demand for offshore wind-farm support vessels (WSVs) in Europe is approximately 30 new vessels a year for the next ten years. Boat-builders are competing worldwide for a share of the market, and water-jets are making a growing contribution to the propulsion systems chosen.
Typically WSVs are required to run at high speed to and from the wind-farm, but when at a turbine they must push hard against fender-posts and hold against wind, waves and current while people transfer to the turbine installation and equipment is offloaded. Water-jets are favoured over propellers when operating in shallow water.
Speaking of operations in the UK Gunfleet Sands offshore wind-farm, Andy White of UK boat-builder CTruk Group says: "We've noted several incidents of ropes and debris damaging propellers. Many of the vessels on the Gunfleet Sands project equipped with conventional rudder/propellers experienced problems holding station on the wind turbine boat landing with strong ebb tides. The ability of water-jets to hold the vessel against a sideways tidal component was significantly better. Water-jets also have a safety advantage in a man-overboard situation, due to the absence of exposed rotating parts and the excellent close quarters manoeuvring."
One of Ctruk's latest vessels is 'Advance', a 15-metre catamaran powered by two Rolls-Royce FF41 water-jets. According to Rolls-Royce, the pump performance has been improved in both the aluminium FF and stainless steel A3 series, resulting very high static thrust, exceptional cavitation margins and excellent performance over the whole speed range. A new control system makes operations easier and safer as engine RPM and clutch controls are integrated to the control system with several safety interlocks to avoid potentially hazardous situations arising.
Global Marine Design of Australia is supplying another UK boat-builder. Alicat Workboats has just placed a second order with the company for a vessel with water-jet propulsion after the success of the 17-metre vessel 'Marianarray', capable of speeds over 30 knots. 'Marianarray' is propelled by two Rolls-Royce FF500 wajterjets and was constructed from a flatpack kit supplied by Global. Unique to Global is a special bow boarding arrangement that can be adjusted to suit various platforms.
Austal has established itself in the WSV market with its Wind Express series of catamarans. The latest order is for three 21-metre vessels, which will have twin MTU engines each coupled to a Rolls-Royce 45A3 water-jet. These vessels will be built in Australia for Turbine Transfers in the UK and delivered in 2012. The 7.3-metre beam catamarans will have a fine entry chine hull-form and a large tunnel height for operation at up to 30 knots. Their targeted sea-keeping ability is up to two metres significant wave height.
HamitonJet of New Zealand is also supplying to the wind-farm support market. The first vessel to be built with their water-jets was 'Windcat 21', constructed by AF Theriault & Son for the UK/Netherlands-based Windcat Workboats. The water-jets' excellent low-speed thrust was desirable for the 18-metre vessel to ensure its step-over system could allow crews to transfer safely to turbine installations in all sea conditions.
'Pura Vida' is HamiltonJet's latest success. Built by Alnmaritec in the UK and operated by North Sea Logistics, the 16-metre Pura Vida is the seventh of the highly successful Wave Commander class of wind-farm support boats to be delivered by Alnmaritec. Powered by two Scania DI16 engines coupled to Hamilton 403 water-jets, the vessel is, says HamiltonJet, exceptionally manoeuvrable around the wind turbines and provides a smooth ride as a result of well-proven sea-keeping characteristics. Several other WSVs are in the pipeline for HamiltonJet.
Wendy Laursen