As the size and distance from shore of offshore windfarms has grown, the cable-lay vessels and equipment sector is reacting with new developments. What will be the requirements for the next generation?
The Next-generation cable-lay vessels and technology webinar was sponsored by MAATS Tech and featured MAATS Tech business development director Gavin Rippe, Nexans vice president installation and services Bjørn Ladegård, and Prysmian Group executive vice president project business, Prysmian Powerlink president and chief executive Hakan Ozmen.
Are there enough cable-lay vessels? In one of several polls taken during the webinar, 43% felt there were only 75% of the required cable-lay vessels in the global market, and a similar percentage voted for 50%. 13% were of the opinion there was only sufficient for 25% of the global market. Only 1% of respondents believed there were 100% of the required vessels for the global cable-lay market.
Mr Ozmen presented a video of the latest cable-lay vessel to join its fleet. Leonardo da Vinci, with a 17,000-tonne cable capacity, compared with the earlier generation 7,000-tonne cable capacity of 30-year-old Giulio Verne, illustrates the economies of scale in the sector. He noted the fall in the cost of offshore energy installations is related to the rise in the number of offshore wind installations.
The driving factor in the sector is the increasing distance from shore, an area Prysmian and newly-launched cable-lay vessel Leonardo da Vinci is expected to service.
“Offshore wind in the energy transition is a success story. The success comes from the cost reduction of the overall energy generation permit per dollar value,” said Mr Ozmen.
For the cable business, every gigawatt of installed power in Europe is worth approximately €300M (US$356M) in cabling business, noted Mr Ozmen. Issues on the horizon for the cabling business include longer connectors.
Longer cable connectors mean longer length and fewer campaigns, “automatically, that drives the cost of the whole project down.” But it is not just cost. The industry faces the challenges of cabling deeper, with higher power and longer length and now the new challenge of preserving the world through the use of eco-friendly materials, said Mr Ozmen.
Prysmian Group is meeting these challenges through new vessels such as US$170M Leonardo da Vinci equipped with more efficient, greener engines, NOx reduction systems, DP3 station keeping, burial capabilities, and, of course, 600 km of Prysmian’s own cabling.
Leonardo da Vinci’s first task is the Sofia Project, installing 44 km of 320-kV submarine HVDC export cables with XLPE insulation. Looking ahead, Leonardo da Vinci is capable of working on the new developments of large offshore floating windfarms and substations. Mr Osmen noted that in the Mediterranean, this will require up to 3,000 m of cables and chains, an installation Leonardo da Vinci is capable of doing.
The next-generation cable-lay vessels are not solely focused on deepwater tasks: there is the shallower water task of laying cable arrays. Next-generation shallow water cable-lay vessels were the focus of Mr Ladegård.
Although there are similarities between deepwater and shallow water drivers, such as high-capacity payloads, the reasons may be different. In the case of shallow water operations, the high-capacity payload is due to the requirement to handle bulky three-core cables. Of course, shallow water capabilities are required and the ability to handle integrated landfall operations.
The key word is integrated. “I will stress one point, over-arching all these capacities and capabilities, is the need for an integrated approach to cable design and installation operations. That is vital,” said Mr Ladegård.
An example of this approach is Nexans’ latest cable-lay vessel newbuilding, Nexans Aurora, which, Mr Ladegård said, “we have incorporated 70 years of experience of installing submarine power cables.”
This is clear in the loads the vessel is capable of handling when laying cable to depths of 3,000 m. The vessel uses caterpillars, a 10-m cable capstan of 75 tonnes capacity, 10-m diameter overbearing wheels and active-heave compensated tension winches. All of which protects the armour of the cables during handling.
Are protection solutions more important that laying solutions? Perhaps not surprisingly, the audience was split on this question, with 65% choosing ’value them equally’. Nearly a third (31%) agreed that protection solutions were more important, and only 4% disagreed.
These features will allow the vessel to adapt to the expected forces to come, such as laying dynamic cable for far-from-shore offshore windfarms.
In a poll concerning cable-lay priorities, 41% believed long, deepwater connectors are required, 34% floating, and 25% fixed bottom array.
Turning to the requirements of shallow water, Mr Ladegård said, “You could choose deploying several vessels, or you can try to get everything done with one vessel. That is not always possible, but it is a good philosophy to try to deploy as few vessels as possible.”
This was confirmed by a poll of delegates: 84% agreed that a cable-lay vessel equipment spread should attempt to address more than one market (16% disagreed).
Nexans Aurora draws very little water (5.5 m) and can operate close to shore, aided by eight integrated high-capacity workboats which are deployed using a ski lift-carousel cradle and launch system. In addition, there is a dedicated float-handling system with hydraulic man-riding baskets. “All these elements are to reduce risk and make the (cable) pulling a safe operation for the cable, to the personnel and to the schedule,” said Mr Ladegård.
Much of the cable-laying equipment for the vessel was designed by MAATS Tech in the UK, including the vessel’s carousel, which will carry cable in an innovative ‘carousel-in-a-carousel’ arrangement that will allow it to carry more cable without significantly increasing the vessel’s size or cost. The concentric carousel-in-a-carousel concept on Nexans Aurora can process two cables (5,000 tonnes) simultaneously or store a single length weighing 10,000 tonnes.
Mr Rippe was available to expand on the company’s contribution to the advancement of cable-laying. He emphasised the unique design features incorporated in Nexans Aurora which derisk the cable-laying environment and the tensions on the cable, which is driven by the vessel client’s requirement to reduce the number of joints.
“The least number of cable joints that you can have is key to these vessels. Hence you are seeing these big payloads and these really big top tension and cable capacities. At MAATS, we prefer to supply a complete system and this derisks the interface aspects of a new cable-lay vessel,” said Mr Rippe.
The bulk of the delegates (75%) agreed or strongly agreed with this philosophy, when asked, “A turnkey offering (supply + installation) is better than split contracts.” 20% valued turnkey and split contracts equally. Only 5% of delegates strongly disagreed or disagreed on this issue.
Mr Rippe noted that for cable-array work, the requirements are different, mainly the volume of the cable, and MAATS Tech is working with Van Oord to produce an 8,000-tonne dual carousel array cable-lay vessel for launch in 2023. This vessel is designed with global operations in mind and carries a full complement of crew and cable to be able to lay array on the US Continental shelf without falling foul of the US Jones Act. “The design of this vessel looks at derisking future project profiles,” he said.
Floating wind is another area MAATS Tech is studying, working on the assumption this will be more prolific than fixed windfarms in deep-water regions such as Japan, South Korea and the Pacific.
Mr Rippe warned the scale and volume of floating wind is very different. As well as dynamic cables, there will be buoyancy modules, rigid connectors and significant quantities of mooring chain. The cable-lay technique will be different, and there is the need to transport mooring chain. “The floating windfarms, in scale, will consume more in chain than any other offshore projects globally,” he said.
In scale, it will be more than an FPSO, and multiplied by 100s for the floating windfarm as a whole. This will be a significant transport and installation challenge for the next-generation cable-lay vessels.
There was an interesting difference of opinion to the poll question: After-sales agreements such as service and repair preparedness are... 75% chose ’Very important to have in place with the contractor as part of the main contract’ while 25% opted for ’Better to defer to after delivery so operations organisation can look for best solutions available.’ No delegate picked “Not crucial. The project handles the most important requirements using third-party verification and insurance representatives.”
What does the future hold for the cable-lay market? Will cable-lay vessels continue to grow in size? Mr Ladegård replied to these issues that having analysed the factors, in most case, bigger will be better. But looking at the sheer size of the market, he noted there will be a need for a distribution of cable-lay vessels across the different size ranges.
Mr Rippe said MAATS Tech is asked to undertake these studies across a range of geographical regions. One constant, is there is a demand for more payload and that increases the dimensions of the vessel. He added that the cost increases, too.
He also said there are a lot of oil and gas construction vessels that might no longer have as much work in the future. These may be available at advantageous prices that would allow conversion.
Mr Ozmen agreed that simple economies of scale led to larger vessels, especially for distant work, which cuts down on the need to return to pick up more cable. In his opinion, a converted vessel would not be as efficient as a purpose-built cable-lay vessel.
On the question of decarbonisation and energy supply, Mr Rippe noted that vessels with battery storage on board can top-up the batteries via the energy produced by the cable-lay equipment during the act of cable-laying. The stored energy in the batteries is then used in port to drive the cable-loading operation, resulting in a quieter, more eco-friendly operation.
Mr Ozmen’s takeaway was that the industry is at an inflection point. Cable-lay vessels will be required to work in deeper, more challenging waters and that floating energy is going to bring a new challenge.
Mr Ladegård noted that a key factor will be future developments in cable. Lighter cabling will have a significant influence on the capacity and energy requirements of cable-lay vessels. He added, “an IMR service agreement or repair agreement should be thought about and incorporated at an early stage in the contracting. That is my key takeaway.”
Mr Rippe’s takeaway concerned the direction of the market. “Floating wind is on the rise, and it will be here to stay. There will be a lot of challenges around handling the equipment required by those kind of windfarms.” He noted that a requirement for two functions can be incorporated into the design of a vessel. The addition of a new requirement, such as floating wind, adds complications. In summary, he noted that the design stage of a vessel is crucial for cable-lay vessels that have a 25 year-plus working life.
From left to right: MAATS Tech’s business development director, Gavin Rippe, Nexans’ vice president installation and services, Bjørn Ladegård, and Prysmian Group’s executive vice president project business/president and CEO Prysmian Powerlink, Hakan Ozmen.