Feature 1 | DANISH MARINE INDUSTRIES Bigger wind comes out of Blue
Blue Ocean Ships has finalised development of a new wind turbine installation vessel, designed to meet current and future requirements of wind farm developers.
dedicated wind turbine installation vessel, Resolution, in operation since 2004, has returned with a new specialised ship for new Danish ship management company Blue Ocean, designed for operations on a wider scale. The ship is designed for unrestricted
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worldwide service and tenders for a number of vessels have been finalised. Blue Ocean Ships is now in the process of negotiating the construction contracts for an as yet unpublicised number of vessels. “As offshore wind park development
has become more ambitious, the trend has clearly been to move to larger turbines and into deeper water in search of more productive wind fields,” said Ken Goh, Knud E Hansen manager, mechanical projects. “Such an example is the London Array, which will eventually consist of more than 300 turbines up to 7MW in size. Tis next generation of vessels, with a length of about 160m and breadth of 42m, will be radically different and significantly larger than any other similar vessels, and are designed to install the next generation of 5MW-10MW wind turbines in waters over 60m deep.” A key requirement for the new design
was to expand the operational envelope, not only with respect to water depth but also to other environmental factors, such as wind and wave conditions, to maximise the number of operational days the vessel can be used to install wind turbines. Operations in shallow waters and tidal areas are also accommodated by the use of specially designed air-cooled machinery systems. Te new vessels will be able to perform
all the necessary stages of wind turbine installation without support from other vessels, from pile driving foundations to the installation of transition pieces, turbine towers and finally the nacelle and blade assembly itself. Te capacity will be much
26 Blue Ocean’s proposed new generation wind turbine vessel.
higher than before and the installation process will be optimised by reducing the amount of on-site assembly for a wind turbine to the absolute minimum. For example, the vessel’s deck is designed to carry the whole turbine tower as a single unit, instead of a number of sections that would need a time consuming stacking and fastening process. Te goal is to be able to install one complete wind turbine topside each day, thereby significantly reducing the cost of offshore installations. A 1200tonne main crane rotates around the aſt starboard leg to provide the flexibility required for the installation of the tower and nacelle components of future wind turbines, which tend to become even bigger. Te vessels are designed to be able to install a 500tonne nacelle at a height of 120m above the water. A smaller auxiliary crane, mounted amidships, supports loading operations and reduces port time, while a further aft-mounted auxiliary crane supports man-riding operations to and from the tower bases. Six truss structure legs and specially designed high-speed jacking mechanisms
will give the vessels what is said to be unrivalled capability and safety. “There have been several accidents
with three and four legged jack-ups,” Mr Goh notes. “Unstable clay sea beds, scouring due to ocean currents and punch-throughs make jacking operations risky, but are a necessity for installing the delicate turbines. Te new vessels will have to jack up and down many times a week so the safety issue was paramount. With a vessel this size, there aren’t too many options for getting help if you get stuck. We can lose footing on one leg completely and still be able to recover safely. Most current jack-up type installation vessels can only use their legs to stabilise themselves, and cannot jack completely out of the water. With the powerful jacking mechanisms and increased leg length afforded by the truss structure, these vessels can quickly jack high above the sea, increase the operations weather window and ride out storms instead of having to run for shelter,” he said. Te vessels are powered by a 20MW
The Naval Architect April 2009
openhagen based consultancy Knud E. Hansen A/S, which developed the world’s first
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