operations & maintenance


the crane installed in the turbine. The report identifies 33 jack-up


vessels that have experience of and are suitable for use in offshore wind operations. Of these, two are specific O&M vessels (and a further two are being built at present). Nearly half the vessels identified are multipurpose vessels and could redeploy onto oil and gas projects if there was a large surge in demand and corresponding uncertainty in long-term windfarm assignments. The longest experience of operating


offshore windfarms is in Denmark, and analysis suggests jack-up vessel tasks remain necessary as turbines age. The total number of global offshore wind turbines in operation for more than 10 years is still relatively small, and there are key design differences between


owners. This will be helped through contractual alignment or ‘in principle agreements’ between neighbouring sites to allow them to contract vessels more quickly. Collaboration has the potential to reduce duplication and increase the efficiency in the way essential tasks such as vessel due diligence, consenting, vessel audits and owner representation are carried out. There is also scope for more efficient sourcing of specialist tools and skilled, experienced labour, The Crown Estate notes. A summary of potential savings


Huub den Rooijen: “report is part of our


strategy to encourage the industry to work together and help bring down costs”


some of the oldest turbines in operation and those being installed or planned currently, making it difficult to predict long-term failure rates. While there is limited experience in the UK of operating offshore windfarms beyond the first five years of their life, emerging industry benchmarking/performance schemes such as SPARTA will help to improve knowledge of long-term failure rates, which is key to ensuring owners select robust strategies for main component maintenance. Jack-up clubs can provide a more co-ordinated pipeline of work for jack-up vessels in the O&M phase and increase the likelihood that suitable jack-up vessels will be available to undertake repairs when required. The risks of extended downtime due to lack of availability of a suitable jack-up vessel can be effectively mitigated through collaboration – models for achieving this are presented in the report. Campaigns across multiple sites within a cluster have the potential to reduce jack-up vessel costs by increasing the scale of repair campaigns, reducing mobilisation and transit costs and reducing the associated weather risks. Improvements in information sharing and co-ordination could help to increase the number of ad hoc collaborative campaigns. “Experience has shown that streamlined planning,


improvements in the availability of site and survey information and sharing information on future jack-up vessel requirements will deliver value-adding improvements for all


through reduced costs and lost- production risk is shown in the table. This indicates a strong case for further work to improve the efficiency with which jack-up vessels are deployed in O&M. The total value realised will


be dependent on actual failure rates, the structure and risk- sharing arrangements in maintenance contracts as well as the availability of jack-up vessels to work at operational sites. While greater collaboration can reduce the annual investment owners need to commit to secure jack-up vessels through long-term charter agreements, it is possible if failure rates drop that some owners may not consistently see a return on this investment in club membership – the key influencing factors are failure rates and availability of suitable jack-up vessels on the spot market. More detailed assessment of likely future failure rates and turbine-specific reliability studies are required to help to inform value assessments further. “The flexible jack-up vessel club concept offers a low risk solution to enable the value of both improved planning and faster deployment times to be realised, and this has been seen in practice during the recent east coast windfarm shared campaign,” the report concluded. “Improvements in the reliability of current and future turbine models, increased ability to undertake in situ repairs of main components and improvements in predicting failures have the potential to reduce the need for repairs that require a jack-up vessel. There may also be options to modify turbine cranes or utilise new approaches in lifting operations to enable more main component replacement work to be carried out without resorting to a jack-up vessel.” OWJ


Charter rates vary widely


Charter costs for jack-up vessels for use in O&M typically range from £45,000 to in excess of £100,000 per day. Longer-term charter agreements will typically attract a lower charter rate, whereas unplanned short-term tasks will see higher rates based on conditions in the spot market at the time of negotiation. As The Crown Estates notes in its report,


market conditions at the time of the charter can greatly affect costs, leading to potential long- term uncertainty. Studies to model jack-up vessel costs suggest that there can be up to 40 per cent difference in costs between a long-term agreed


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charter and rates on the spot market. This is accentuated during periods of high demand for jack-up vessels and can also vary seasonally. Costs of heavy-lift jack-up vessels during the O&M period, therefore, represent a large risk unless contractual rates can be locked in through long- term arrangements or by other means. There are examples of some jack-up vessel owners


offering fixed-cost jack-up operations in other parts of Europe, although this is not currently widespread. As cluster sizes grow and if seabed conditions allow, this may become a more common, alternative form of contracting in the future.


Offshore Wind Journal I 3rd Quarter 2014 I 43


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