The Damen WOLF 2500 a high-efficiency solution for tomorrow’s super-sized wind turbines
Sjaak Jan Jiskoot
Damen’s Offshore XL team
As a leading designer and builder of specialist vessels to serve the needs of the offshore energy sector, Damen maintains close contact with companies across the industry. By gathering feedback and opinion it can not only update its current designs in line with changing operating requirements and new technologies, but also look ahead and explore concepts and capabilities that might be needed in the future.
Winds of change
No maritime sector is growing and evolving faster than that of offshore wind where, in the race to cut the costs of installation and generation, the wind turbines are growing rapidly in size and output. Part of the quest for maximum efficiencies is the requirement for vessels that can install and maintain the turbines quickly and cheaply, and one particular area that industry players have indicated as being ripe for modernisation is the vessels used to install the turbine foundations.
“Currently the vessel of choice is the traditional heavy-lift vessel, originally developed for the offshore oil & gas markets,” explains Sjaak Jan Jiskoot, product manager at Damen’s Offshore XL team. “They are widely available and have plenty of lifting capability, but they were not designed for the specific needs of wind turbine installation. They are engineered for a limited number of lifts at high capacity and to work on conjunction with barges.” The realities of installing wind turbines are quite different. Building offshore windfarms involves large numbers of repetitive lifts, while the use of traditional heavy-lift vessels also brings logistical complexities.
Designing a fit-for-purpose installation vessel
“Our focus has been on optimising the floating solutions,” continues Sjaak Jan Jiskoot.
We have been studying the entire logistical chain with the aim of understanding both the environment in which these vessels work and the technology available.
With the wind turbines of the near future capable of generating 10 to 12 megawatts and over 200 metres in height, one widelyrecognised constraint in the current system that was immediately highlighted is that of ship-to-ship lifts. These are currently an important element for the installation of jackets and monopile foundations carried on barges, and so Damen set out to remove them from the equation.
With the jackets for the future turbines expected to be around 95 metres high, a high-efficiency vessel will not only need extensive deck space to carry them, but also a new generation of cranes to handle their unprecedented hook heights above deck. To achieve the necessary performance in a cost-effective way, studies showed that, rather than lengthening the boom, a better alternative would be to raise the height of the crane post. Keeping the boom short makes the structure relatively light and results in better clearance under the boom. “This indicated that we clearly needed to look at the vessel design as an integral part of the crane specification and geometry so as to come up with an optimised solution for the market,” Sjaak Jan adds.
With the installation and transportation cycles for wind turbine installation involving high numbers of lifting operations, it was determined that a hook load capacity of ‘just’ 2,500 tonnes would enable a compact vessel design yet still deliver a crane capable of handling the majority of expected foundation installations.
The Damen WOLF 2500
The Damen Offshore XL team worked up multiple concepts, and the design that is now being brought to the market is the Damen WOLF (Wind & Offshore Lifting Factory) 2500. As well as meeting the fundamental needs of low expenditure and high efficiency transport and installation, the WOLF 2500 incorporates the results of the feedback process to further boost productivity while reducing installation cost.
The design sets out to limit non-essential equipment and ensure an optimal logistical flow. A state-of-the-art DP system removes the requirement for mooring winches, anchors or wires, and has the added benefit of removing risks to underwater infrastructure and significantly reducing vessel positioning time. By running passageways under the working deck with topside access available at key points, the 80-strong complement can move around the vessel efficiently and safely away from the working areas. 148 metres long, 49 metres across and with a draught of 6 to 8.5 metres, it will be capable of carrying and installing two 1,600 tonne jackets, five 900 tonne jackets or five 2,000 tonne monopiles on a single deployment. Transit speed will be 12 to 14 knots. While the Damen WOLF 2500 is designed specifically for the future needs of the offshore wind sector, its capabilities ensure that it will be able to deliver value right across the offshore markets.
Preparing for market
“With deliveries available from 2020, we are now actively promoting the design in the market and developing a building strategy based on our new yard, Damen Shipyards Mangalia in Romania, which will be very cost-efficient,” says Sjaak Jan. “Looking at the vessels that are currently installing foundations in the North Sea, our design offers twice the capacity of current conversions of the same dimensions.”
The prospects for the Damen WOLF 2500 look good. Following its launch at OTC, Houston, in May 2018, Damen’s CRO (Cruise, RoPax and Offshore) team, recently set up to develop and market large vessels, is touting the concept to existing and new customers, confident that it has the right vessel for the right sector at the right time.