The Morocco-UK Power Project was unveiled by developer Xlinks in late 2021 and – set to have a total capacity of 11.5GW, with a capability of exporting 3.6GW for an average of 19+ hours a day – the announcement was met with much excitement from the UK energy industry.
The project aims to connect a solar and wind farm co-located with a 5GW/22.5GWh onsite battery storage facility in Morocco’s Guelmim Oued Noun region to Alverdiscott near the north coast of Devon, England, via four 3,800km High-Voltage Direct Current (HVDC) sub-sea cables.
Connecting the electricity systems of neighbouring countries, interconnection is a vital implement in reaching net zero. Interconnectors can provide essential grid balancing services by importing and exporting electricity during periods of high and low demand respectively.
Last month, the Morocco-UK Power project hit headlines again as Xlinks reportedly began preparing to commission the “world’s biggest” cable-laying vessel.
Manufacturer XLCC is building the vessel, and is currently in talks with Xlinks on the prospect of making the Morocco-UK project the vessel’s first endeavour.
Current± sat down with Alan Mathers, business operations director and Alex Gorrie, project manager at XLCC to discuss building the “world’s largest” cable-laying vessel and learn more about the process of installing interconnector cables.
How are subsea cables manufactured, and why are they used for interconnections?
“We will make cables in 20km sections called ‘factory lengths’, that will be joined into 160km sections called ‘delivery lengths,’ before they are loaded onto the cable-laying vessel. Each cable weighs 70kg per meter,” Mathers tells Current±.
The reason each section is so long, continues Mathers, is to produce fewer joints – the weakest part of the infrastructure – and create a more robust cable
Mathers adds that he is often asked why subsea cables are preferred to overhead or land cables, to which he responds: speed of installation.
For instance, as Mathers discloses, Xlinks is expected to take six months to install 14km of cable connecting from the sea to the substation in Devon. The vessel that XLCC are creating however, can lay 20km of cable in the water every day, says Mathers.
“When you have a look at how rapidly you [lay cable with] the vessel, there’s clearly an advantage of being able to put in submarine cable rather than either land cable or overhead cable,” adds Mathers.
What sets this vessel apart?
According to Blackridge Research & Consulting, the Leonardo da Vinci Vessel, owned by Prysmian Group, is believed to be one of the largest cable-laying vessels in the market today.
Consisting of two rotating platforms of 7,000 and 10,000 tonnes respectively, the Leonardo da Vinci Vessel is said to be the “highest carousel capacity in the market”.
XLCC’s vessel, Mathers reveals, has been designed to have two carousels capable of holding up to 13,000 tonnes each.
“So we’re roughly double the current largest cable-laying vessel intake in the world today,” says Mathers.
The vessel can also be used for a range of projects, including long-haul interconnector projects, such as Xlinks’, exporting cables for offshore wind farms and grid or network reinforcement projects.
“In terms of the design of the vessel, it will be much larger than other vessels in the market and it will be DP3 compliant,” Mathers tells Current±.
DP3 refers to dynamic positioning requirement ratings for vessels. As the highest DP rating, power plant consultant OneStep Power states a DP3 rating applies to a vessel that can continue operation “with the failure of an active or static component, even with the total loss of the equipment in a compartment to fire or flood.”
Mathers adds that as the centre of rotation is in the vessel’s middle, it will be more stable in the water.
“In theory, [the vessel will] be able to lay cable for longer throughout the year on a slightly higher sea state where the weather’s rougher”, continues Mathers, “so although we’ve got much more payload available to us, it’s at no additional cost in terms of operating efficiency.”
What does the cable laying process look like?
Project manager at XLCC, Alex Gorrie explains the cable-laying process once the cables are set on the vessel’s two storage carousels in the order they will be placed on the sea bed.
In terms of deploying the cable on the seabed Gorrie said that, although design is still in development, he can reveal that XLCC has “opted for a solution using linear cable tensioners which electronically grip onto the cable on the vessel during cable deployment operations.”
A remote-operated vehicle will sit at the bottom of the sea bed using its camera to ensure the cable is being laid safely and record the exact coordinates of where the cables are placed to help identify where to join the new cable.
Cables will be laid 160km at a time bundled in a pair configuration which, depending on the length of the cable, will include a fibre optic cable that will stay under the sea to monitor the health of the cable using both temperature and acoustic sensors. This will alert XLCC to the exact location of any problems in the cable.
There are three to four process to bury a cable once its been placed on the seabed. According to Gorrie, the most likely process to be used for the Xlinks project would be pre-trenching the seabed, laying the cable, and then burying it.
Since talks with Xlinks began, Mathers revealed that the length of the cable required has increased from 3,800km to just over 3,900km due to the necessity of navigating seabed canyons in the path of the cable.
Building the Morocco-UK cable
Talks between XLCC and Xlinks are ongoing and a contract is yet to be finalised as the company waits to see whether Xlinks is successful in receiving a contract in the UK’s Contract for Difference (CfD) scheme.
Xlinks has made its intention known to bid in the UK’s CfD scheme, making the project a source of revenue rather than cost by delivering energy at £48/MWh.
If the partnership is confirmed, Gorrie estimates the the process between contract signing and delivery of the vessel to XLCC’s facility in Hunterston, Scotland will take approximately 27 to 38 months.
“We’re really excited about the impact [the Morocco-UK project] could make on the environment, delivering dispatchable power back to the UK,” Mathers summarises.
“And I think you’ll find everybody on the XLCC team is motivated in terms of reducing the carbon footprint, bringing in more power to the UK and reducing average prices, so it’s a wonderful project to be involved in.”
