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.
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.