DEME’s new SOV Groenewind combines the use of a SWATH hullform, dynamic positioning and a motion-compensated gangway that also lifts cargo
A naming ceremony took place on 25 June 2021 for DEME’s dynamic positioning class 2 (DP2), service operation vessel (SOV). The vessel, Groenewind, is set to enter service under a long-term charter contract with Siemens Gamesa Renewable Energy, transporting technicians to the Rentel and SeaMade offshore windfarms in Belgium.
The innovative 60-m vessel is the first SOV with a small waterplane area twin hull (SWATH) hullform. It is equipped with a motion-compensated gangway to safely transfer maintenance technicians to turbines in significant wave heights of up to 2.5 m. Groenewind has a capacity for 24 technicians plus crew. The vessel will also use daughter craft to safely transfer technicians to wind turbines.
The design was developed by DEME in close co-operation with Vuyk Engineering Rotterdam and Maritime Research Institute Netherlands. A keel-laying ceremony for the innovative vessel took place on 13 December 2019 at Cemre Shipyard in Turkey.
The SWATH hullform will reduce the effect on the vessel of wave impacts when approaching wind turbines, compared with a conventional monohull SOV. DEME claims that compared with a conventional hullform, the SWATH hull reduces fuel consumption by up to 50%.
SWATH hullforms have been used on several vessel types before, not least on naval vessels and pilot boats, but the DEME ship is its first application in the offshore wind sector. The concept is said to date back to a patent awarded to Canadian Frederick G Creed in 1938. A dive support vessel with a SWATH hull entered service in the Netherlands in 1968. The US Navy commissioned a SWATH ship, Kaimalino, in 1975 and in the 1990s two 25-m SWATH pilot tenders and a larger, 50-m unit were built by German shipyard Abeking & Rasmussen.
The SWATH hullform is like that of a catamaran but with unconventionally shaped hulls that operate below the waterline. These submerged hulls provide the necessary buoyancy, but at the waterline the vessel has very little waterplane area, which reduces the forces acting on the vessel. This means the movement of the ship caused by external forces is very much reduced, resulting in a very stable unit, even in heavy seas.
The motion-compensated gangway was supplied by SMST and has new functionality in the form of a cargo transfer system that runs underneath it.
A winch is installed at the tip of the gangway to provide motion-compensated lifting. The winch is designed to move beneath the gangway, along its entire length. The lifting capacity is fully 3D motion-compensated, and in addition to lifting loads onto a wind turbine, also enables ship-to-ship lifts to crew transfer vessels.
Groenewind is an environmentally friendly vessel, and with reduced fuel consumption and emissions in mind, it has a waste heat recovery system and Clean Design class notation.
Speaking at the time the keel of the SOV was laid, DEME Offshore business unit director Michael Glavind said, “With DP2 capability the vessel will be able to hold position in rough sea conditions and operate with reduced fuel consumption compared with conventional SOVs.
“We believe the twin-hulled design, a motion-compensated gangway and dynamic positioning is a winning combination and will further reduce the cost of windfarm maintenance compared with large monohulls.
“With this first SOV joining our fleet, we are further strengthening our capabilities and are able to offer the full offshore wind package, from installation to maintenance.”
Siemens Gamesa head of offshore logistics Rene Wigmans says, “Siemens Gamesa is dedicated to finding flexible, competitive solutions. The Rentel and SeaMade windfarms make up the largest wind power installation in Belgium. Groenewind will enable us to optimise operation and maintenance operations and safe maintenance solutions there.”