WTIVS: Foundation installations – the future challenge?

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The main interview in this edition covers Van Oord Offshore who has recently taken delivery of their new wind turbine installation vessel (WTIV) Aeolus. We now look at what three other companies operating these types of vessels are thinking about now and for in the future.

Depending on your definition of a WTIV there are 25 vessels operating or able to operate in the offshore wind industry. As with most vessel categories the newer vessels are considerably larger than the first generation. There are plans for even larger vessels, including one already ordered from Samsung Heavy Industries, the Seajacks Scylla, which will be the largest of them all when it is completed in the second half of 2015.

Swire Blue Ocean A/S

Lars Blicher is the General Manager & Director of Swire Blue Ocean A/S (SBO) who have two WTIVs in their fleet, the Pacific Osprey and the Pacific Orca. Both of the vessels were built in the Korean yard of Samsung Heavy Industries. They are very large vessels and have capabilities well beyond the majority of the 23 other vessels.

We asked him what will be the criteria for future WTIVs. In his opinion it is the capability of the vessels and not just the size that will make the difference in the future. The facilities of the port where the vessels operate from are already determined with maximum water depths, quay length and lifting reach. It would be a massive added construction cost to the industry if the ports would have to change to suit bigger vessels. The naval architects and vessel equipment designers will therefore have to use the current dimensions.

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The cranes, deck loads and jacking systems will have to be designed to be able to accommodate the heavier and larger individual units of the next generation turbines to be installed in deeper waters. The future towers will also be considerably taller to accommodate longer blades of more than 80m length. As a consequence cranes are needed that are not only able to lift these heavier loads but have a longer reach also. These nacelles and blades present less of a problem which today's fleet would have little or no problems installing.

Main challenge

However, it will be the foundations that will present the biggest challenge in the new wind farms to be built. Currently only four of the existing vessels will be able to handle these larger foundations with a larger deck area footprint.

The industry is still 'experimenting' with the designs for the concept of a new foundation. In late August the Pacific Orca completed the installation of the test design suction bucket foundation on the Borkum Riffgrund 1 wind farm. The 'test' is being carried out in cooperation with DONG Energy and the Carbon Trust Offshore Wind Accelerator programme. The single foundation weighed 850t, which alone is not a challenge as the monopile foundations installed by the same vessel on the same wind farm weighed up to 630t and all are well within the 1,200t lifting capacity of the vessel's main crane. But this was only one foundation to be installed and more will have to be loaded for installation each time if it is not going to add even more to the overall installation costs. Mr Blicher told Offshore WIND: "The design of vessels for the installation of a foundation for deeper water and a heavier load will have to wait until the optimal design of this foundation has been developed and production lines are available for fabrication."

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SBO see the six legs design of their vessels to be the way forward in the future. The weight spread of the deck load is less critical allowing for a lighter vessel construction to carry the same load. There is another advantage gained with the constant jacking procedures required to meet a rate of 10 turbines installed in 10 days, a rate achieved recently by the Pacific Osprey on the DanTysk wind farm. The six legs design allow easier solutions freeing a leg which has become stuck in the seabed during jacking up operations. But Mr Blicher would not rule out building a four legs jack up in the future. They see a 25 year life span for the vessels but, in common with almost every company we have spoken to, new buildings would only be ordered if a long term prospect was in sight.

SBO are very pleased with the Pacific Orca and the Pacific Osprey as their operations to date have been successful. In the mean time when 011 & gas contracts come up they take them, as these large WTIVs have already proven successful here, attracting repeat contracts in this sector. However the two vessels will be working in the offshore wind sector in the future, in the industry for which they were designed.

MPI Offshore

Paul Gibson, the MPI Chairman, sees not only a new build as the answer to future project efficiency and cost reduction but also clever engineering and stable, well planned projects with larger turbines.

Clever engineering

He is realistically confident that "their vessels will be able to handle most things albeit not in the numbers we could have done with the 3.6MW turbines". Before reaching this level of ability there will be the application of some clever engineering. Certainly on the two big vessels, MPI Adventure and MPI Discovery, they have already looked at upgrading the legs for deeper water up to 55m and the cranes for 800 to 850t monopiles with a bigger radius.

The cost of the electricity produced is set to decrease by 30% just by using 8MW in place of the 3.6MW turbines.
Being able to install these larger turbines will significantly decrease the overall cost. It follows that if you can use existing vessels to carry out these larger turbine installations then that will harden the cost reduction.

The right conditions

MPI does have plans to build a new, larger vessel, but only if the UK government can create the stable conditions required to produce the long term sustainable industry needed in order to get a return on the investment required for the new vessel. Continued erratic budgeting will not bring the necessary conditions for a stable market. Of course other countries should also be included but the huge UK opportunities dominate the industry market now and in the foreseeable future. The required conditions would nurse a supply chain which in return would encourage investment, including, he hopes, attracting MHI Vestas into the UK with a factory.

Mr Gibson also recognises the need for "pukka" (a Hindi word meaning solid, well formed - Ed.) foundation installation vessels. He estimates that half of the current WTIVs will not be able to compete in the future conditions. They can install turbines - but it stops there. Getting the right and sufficient vessels for installing foundations is a priority.

The major concern he has for the future is the lack of cabling, especially interfield cabling, expertise and he is planning to address this situation during the installation of the foundations by taking a day longer on the location and getting these cables laid and connected by themselves. With his oil & gas background he is used to EPC contracts with one contractor looking after the installation and commissioning. It is in this direction that he would like to take the MPI vessels.

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The future however is not going to 'take off until 2017', which, given the correct conditions, would be right for the delivery of the new vessel he has in mind. In the meantime the two big vessels will be kept busy and the MPI Resolution, he predicts, will not suffer too badly due to the vessel's design features including shallow water ability to dry out on the sea bed at low tide, as the vessel was built with engines cooled by an air cooled water circuit for this purpose.

Although a new build is included in the future, Paul Gibson's vision of the future is wider than just the vessel. It includes a change of thinking, taking a direction out of the box. This would not be the first time he has done this and the MPI Resolution is the result of a previous occasion when he thought 'out of the box.'

A2SEA A/S

Jens Frederik Hansen is the CEO at A2SEA A/S, the company which by any standard has installed the largest number of turbines to date. Last year in June they celebrated the installation of their 1,000th turbine.

The Danish company has two new WTIVs built by the COSCO Shipyard Group in China. The latest vessel, SEA CHALLENGER, was delivered to the company in Esbjerg in May this year, a bigger sister to the SEA INSTALLER which started work in January last year. Bigger because the new vessel has a main crane with a maximum lift capacity of 900t compared to the 800t main crane on board her sister vessel. This difference is an indication of the fact that the future lies with even larger turbines engineered for offshore.

Floating deep sea options

With wind farms being planned further out to sea in deeper waters we asked Mr Hansen whether A2SEA would consider ever ordering a floating crane in the future. His answer although none specific in detail was that they have considered this option. The design would definitely be for a crane vessel rather than a crane barge, able to work in heavier seas and the self-propelled factor being a very necessary detail. With the difficulties in overcoming the motion factors involved in the installation of the turbines and blades he could see that such a vessel would be more involved in the installation of foundations. For foundations such a vessel would have definite advantages being able to handle the ever increasing sizes and design formats of foundations.

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There would be no necessity for a super lift weight as installed on crane vessels designed primarily for the oil & gas industry, but Mr Hansen would not be drawn to reveal further details at this time.

Modification options

Talking further on the two new vessels, the Fredericia based company is very pleased with the performance of both the SEA INSTALLER and SEA CHALLENGER which has exceeded their expectations. The original design of the vessels included built-in options for modifications to the cranes for extended heights and to the legs so that they can have them lengthened in the future. Other modifications possible included the helideck that has recently been retro fitted on to the SEA INSTALLER, in recognition of the advantages for helicopter crew changes when further away from the coast.

The company is owned by two shareholders who between them are the largest offshore wind farm developers and operators in the world and the turbine manufacturer with the largest market share of offshore wind turbines. However A2SEA is a powerful company in its own right with a proud record in the offshore wind industry.

Foundation vessels

All three of these top men recognised one major bottle neck problem in the future - there are not enough vessels capable for installing large foundations in the future. Does anyone have any ideas when they will be built and for whom?

As we were getting ready to go to press we received details of the MPI Endeavour which had already been heralded as being big. Here are the details of the vessel which show that it certainly will add new limits in all dimensions to this class of wind turbine installation vessels.

wtivs

Dick Hill

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