Specialised vessels cut costs

WORLDWIDE: A new generation of purpose-designed service jack-up vessels can offer lower day rates by being able to operate in tougher weather conditions.

New… DBB's Wind Server can operate in rougher seas
New… DBB's Wind Server can operate in rougher seas

Reducing operations-and-maintenance (O&M) costs in the offshore wind sector is part of the mosaic of interlinking efforts to cut electricity generation costs. New special-purpose service jack-up barges due to enter the market within the next two years are expected to make an important contribution to cutting O&M expenditure. The cost of a five-day deployment could be reduced by some 12%.

The daily hire rate of the new smaller jack-ups will be considerably lower than for the often much-larger installation vessels currently used, which cost about EUR 200,000-300,000 a day. DBB Jack-up Services, an offshore service provider based in Denmark, expects delivery of its first purpose-designed service jack-up Wind Server vessel next summer and anticipates charging about EUR 70,000 a day for shortto medium-term contracts, with a discount of around 10% for long-term contracts of three to five years.

But the company stresses that the real savings lie in the weather criteria under which the new vessel can be deployed. In a rough calculation, an existing jack-up of comparable size with a weather limit for working of up to 1.5 metre significant wave height (Hs) could cost a day rate of about EUR50,000 and work 200 out of 350 days a year. This will give an operational rate of EUR 87,500 per day.

The company claims the new Wind Server will be able to work at 2.0-2.5 metre Hs at a day rate of EUR 70,000, giving it 320 potentially active days out of 350. This will give an operational rate of EUR 76,500 per day. Assuming a major replacement takes five days, the customer pays all inclusive EUR 382,800 instead of EUR 437,500, which represents a 12% saving.

"We can't make the jack-up cheaper, but we can make them better, so that the number of days we can work offshore increases and the cost per replacement comes down," the company says, and on a long-term charter agreement the savings will be even more significant.

Port charges

Depending on design, the new jack-ups could also save on port charges. Windea Offshore, a joint venture of EMS Maritime Offshore, Bernhard Schulte Group and SSC Wind that provides services for offshore wind farms, has developed a jack-up service vessel design that, the company claims, does away with the need for jacking-up in port, while at the same time allowing the on-board crane to be used at full capacity. This would eliminate some of the port charges.

Under normal conditions, DBB's vessel will be jacked-up in port for loading. But for some ports that have restrictions on jacking, or where the seabed may be unsuitable for jack-ups, loading can be done without jacking up if required, according to the spokesman. The crane on DBB's vessel can operate even when the jack-up is in floating, albeit at reduced lifting capacity. However, the Wind Server benefits are more focused on improvements at the site, the spokesman stresses.

In addition to component replacement and turbine O&M activities, other services from Wind Server include deployment of remotely operated vehicles for inspecting the foundation, scour protection, marine growth and other required monitoring.

The new generation of O&M vessel designs, tailored for the needs of offshore wind, marks the beginning of a new wave of cost-cutting that, added together, could drive offshore wind cost-of-energy substantially down within the next few years.


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