Danish consultancy Knud E Hansen has unveiled a new, highly capable, environmentally friendly wind turbine installation vessel for the offshore wind market
The Atlas C-class vessel has a jacking deadweight of 18,000 tonnes, 6,800 m2 of deck area and a crane capable of handling 3,000-tonnes at 37 m. The company claims the Atlas C is “currently the only wind turbine installation vessel capable of carrying six new-generation 14-16-MW offshore wind turbines” and “at least five next-generation 20+ MW turbines.”
The company said the jacking deadweight and crane capacity of the new design also enables the vessel to carry at least four extra-large monopile/transition piece foundations of the type required for 14–16-MW turbines.
“The Atlas C-class is intended as a platform which will form the basis for further customisation according to our clients’ objectives,” said the company. “Cranes, thrusters, generators and jacking systems can all be modified and selected based on manufacturer availability such that the vessel can be tailored to suit the individual needs of each client. This represents a significant departure from competitors that offer off-the-shelf products with little flexibility.”
The new vessel has a length overall (excluding helideck) 170.00 m, breadth, moulded of 60.20 m, depth to main deck of 13.20 m, moulded draft at 18,000 tonnes deadweight 6.70 m, and a speed at 6.50 m draft of 12.0 knots.
In keeping with the objective of design versatility, the cargo deck incorporates uniform girder spacing in both longitudinal and transverse directions such that foundations for equipment and turbine parts can be standardised and installed in different locations and orientations.
Knud E Hansen said energy savings and reduced emissions were among the key drivers for the propulsion system. The vessel is powered by eight identical generators, each of 3,340 kW, which are arranged in two independent enginerooms. A DC grid system allows the engines to run at variable speed for maximum fuel efficiency. The DC grid system is coupled to a 4-MW battery pack for load levelling and peak shaving.
The batteries can supply ‘instant power’, which reduces the need for ‘spinning reserve power’ from the generators running on standby, such as during dynamic positioning operations, and make it possible to recover approximately 60% of the energy that is used to jack the vessel up to operational height.
To further minimise power consumption, the vessel is equipped with highly efficient thruster units, including four azimuthing stern thrusters driven by highly efficient permanent- magnet motors and equipped with nozzles for maximum bollard pull.
At the forward end of the vessel there are two tunnel thrusters and two retractable bow thrusters configured to maximise thrust. The platform is equipped with four three-chorded trusswork legs which can support it in water depths up to 80 m.
The spud cans are optimised for the lowest possible seabed penetration and are fitted with buoyancy boxes to reduce draft in port, reduce the load on the seabed when the vessel is jacked up, and to help retract the legs out of a muddy seabed. The platform is elevated by a powerful high-speed electrical rack-and-pinion jacking system designed for 5,000 load cycles. “This is significantly more than many competing designs and will ensure the leg racks will last the lifetime of the vessel,” the Danish designer said. The optimal load balance of the vessel ensures the total jacking capacity of all four legs can by fully utilised in fully loaded condition.
The main deck of the accommodation block includes an operations centre consisting of offices and meeting rooms as well as a hospital, day room, TV room and workshop. Above this is a large galley with spacious mess rooms and ample provision rooms.
The three decks above include 130 cabins for contractors, crew and officers. The top deck consists of a bridge with centreline and wing consoles and a large helicopter deck. Below the main deck is a gymnasium, cinema, TV room, games room, and sauna as well as a laundry room and storerooms.
Knud E Hansen said negotiations are currently ongoing with companies in the offshore wind sector to further develop the Atlas C platform based on their individual requirements. It describes the new class of vessel as the first in a series of planned wind turbine installation vessels of varying sizes.
One of those already under development is a smaller A-class platform that can carry four 14-MW turbines and is equipped with a 1,600-tonne crane. This vessel is intended for clients who require a smaller variant to install wind turbines on pre-installed foundations.