Unlocking the renewables potential of the Celtic Sea

10 min read

The Celtic Sea and coastal waters around Wales have a higher concentration of renewable energy resources than perhaps anywhere else on the planet. Andrew Wade explores some of the technology advances - from floating wind to marine energy - that will be key to tapping into this vast resource. 

Blue Gem's Erebus project will see the installation of seven floating offshore wind turbine turbines in the Celtic Sea by by 2026. Image: Principle Power

Over the last decade, the UK has become a global leader in renewable marine energy, tapping into the vast resources its coastal geography offers. Offshore wind, in particular, has flourished, with gigawatt-scale projects being deployed off the east coast of England and Scotland, at Hornsea, Dogger Bank and Moray.

However, looking at a map of existing and proposed wind farms, what’s perhaps most striking is the complete absence of projects in the southwest of Britain, off the rugged shores of Wales, Devon and Cornwall, shaped by the fierce North Atlantic. The Celtic Sea - which extends south off Wales and Ireland down past Cornwall and Brittany to the edge of the continental shelf – is estimated to have around 50GW of wind generating capacity alone. What’s more, it also delivers some of the highest tidal ranges in the world, alongside some of the best waters in Europe for generating wave energy. In a country blessed with renewable resources, the Celtic Sea may well be its biggest prize.

Key to unlocking these enormous marine energy reserves will be Floating Offshore Wind (FLOW). Still in relative infancy compared with the fixed offshore wind we see elsewhere in the UK, FLOW will enable wind farms in the deeper waters of the Celtic Sea, with turbines sitting atop floating platforms tethered to the seabed, in a fashion similar to offshore oil rigs.

“Eighty per cent of the world’s wind resources are in waters deeper than you would traditionally go with fixed offshore wind,” explained David Jones, stakeholder manager at Blue Gem Wind, a FLOW joint venture between energy giant Total and renewables developer Simply Blue Energy. “The Committee on Climate Change have said that we’re going to need over 100GW of offshore wind by 2050 in the UK to get to net zero. At the moment we’ve got 10GW. So that’s a significant increase in offshore wind and floating is going to play a part because there’s only so much real estate that you can get fixed offshore into.”

Based in Pembroke, Blue Gem is set to be the first operator to deploy FLOW in the Celtic Sea, with its 100MW Erebus project having recently been submitted for consent to the Welsh Government. All going to plan, its seven turbines will be fully operational by 2026, powering 93,000 homes. A second project, Valorous, is set to follow, scaling up to 20 platforms and 300MW. “Both projects we’re developing have grid connections into Pembroke and they’re both in Welsh waters,” said Jones. “Wales, obviously, because of its diverse resource in terms of coastal, it’s got one of the biggest tidal ranges and there’s been a lot of activity around lagoons, and then there’s obviously tidal stream and wave as well. I guess the difference between floating wind versus wave and tidal is probably just the scale and the investment appetite as well…essentially, we’re taking two proven technologies, right? We’re putting a wind turbine on top of an oil & gas platform. So from that aspect, investors understand it.”

Principle Power has been selected as the platform supplier for the Erebus project. Its three-column, semi-submersible WindFloat uses five-line catenary mooring and is equipped with a closed-loop ballast system to compensate for changes in wind velocity and direction. The technology is already deployed off the coast of Portugal in the WindFloat Atlantic project, as well as off Aberdeen at the Kincardine wind farm, which is currently claimed to be the world’s biggest FLOW installation, though that is a title set to change hands several times over the coming years as the sector matures.

Getting the Welsh ports and supply chain up to speed is set to be a key factor in tapping into the Celtic Sea resources. Image: Blue Gem Wind

The deeper and often wilder waters where FLOW is effective means positioning these giant floating structures safely and accurately is no easy feat. This is where the experience of offshore operators like Total comes in. Oil & gas players have been working in the deep  waters around Britain and Ireland for decades. That expertise now provides an opportunity to pivot into greener energy production. Away from Erebus, Simply Blue is also working with Shell on two floating wind projects off Ireland’s coast. “It is a space that the oil & gas majors feel that they can really come in with intent,” said Jones. “I think that they obviously have ambitions to get to net zero themselves as companies and I think it’s the scale that they like.”

While the size of the opportunity may be huge, Blue Gem is advocating a stepping-stone approach to FLOW in the Celtic Sea, starting off with demonstrator projects then scaling up incrementally. According to Jones, this model gives both the ports and supply chain time to grow in a more organic way. With no real offshore industry to speak of, the Celtic Sea is playing catch-up in this regard. “Essentially because of water depth, historically the supply chains are not as mature as those on the east coast and the North Sea and the Irish Sea, perhaps, and the same with the port facilities,” said Jones. “If you start with a smaller project, that’s probably the most effective way you can get the local supply chain involved rather than going straight to a commercial scale project where a lot of the supply chain would obviously have to come from external (sources).”

But not everyone is necessarily in agreement on the stepping-stone approach. While it makes sense in many ways – particularly if the aim is to capture as much local supply chain as possible - some argue that the ports need gigawatt-scale projects to hang their hat on and underpin the huge investments required to bring the coastal infrastructure up to speed.

“Having a large-scale pipeline of gigawatts is what the ports say that they need in order to encourage the development,” Jay Sheppard, marine energy project manager at Marine Energy Wales, told The Engineer. “So lots of developers, larger scale developers, coming forward and announcing their intention to develop projects and communicating with the ports has encouraged that development.”

Despite Blue Gem advocating the stepping stone model, Jones understands the conundrum for the ports and the desire to see bigger projects rolled out. He estimates there are about 15 developers exploring the FLOW opportunity in the Celtic Sea, at various stages of progress. For now, however, Erebus is one of just a handful of small projects to have secured seabed lease agreements with the Crown Estate, making it difficult for the ports to fully commit to the expensive upgrades required.  “Ports and infrastructure is a major challenge for us at the moment, I think it’s fair to say, from an engineering and project perspective,” said Jones. “The kit is so big, it’s actually finding ports around the Celtic Sea that we can fit it in, essentially. You can’t spend £100m on your port just for Erebus. So it’s almost like a chicken and egg situation...until the ports have a real sight of a pipeline that’s absolutely coming, and there’s multiple projects with multiple leases, then it becomes easy to make those kind of investment decisions, but at the moment it’s challenging.”

Wales’s geography – particularly its tidal resources – means that every form of marine energy is abundant

For Sheppard at Marine Energy Wales, a big part of his remit is to help support that pipeline. Historically focused primarily on tidal and wave energy, the enormous potential in the Celtic Sea has seen MEW diversify into FLOW in recent years. The organisation is backed by the Welsh government but also exists to represent its members, which include developers, ports and a host of others seeking to tap into Wales’s burgeoning marine energy industry. “We also facilitate a roundtable, the Celtic Sea Developers Alliance,” said Sheppard. “That’s a gathering of all the project developers that wish to pursue projects in the Celtic Sea, getting them to come together and collaborate on common challenges, things like consenting and grid access and leasing.”

FLOW may be grabbing a lot of the current attention, but Wales’s geography – particularly its tidal resources – means that every form of marine energy is abundant. Many readers will remember the Swansea Bay Tidal Lagoon project, a 320MW pathfinder that looked destined to become the first of its type in the world, potentially paving the way for others in Wales and beyond.

The tidal range in and around the Bristol Channel is one of the largest on the planet, and a series of tidal lagoons could potentially have delivered dependable, baseload power to the grid for more than a century. Despite initial positive noises, the UK government ultimately withdrew support for Swansea Bay Tidal Lagoon in 2018. Not to be deterred, the Welsh Government has since picked up the baton. “I think there is a little bit of shared frustration that lagoon has not been built yet, but there’s a lot of interest in making that happen,” said Sheppard. “Now there’s the Welsh Government Tidal Lagoon Challenge. Welsh government have committed to enabling Wales’s first tidal lagoon.”

MEW is engaging with stakeholders to determine the level of interest in developing the tidal head resources on the Welsh coast, and further announcements are expected this spring. In addition, a new tidal scheme for Swansea Bay - known as Blue Eden - is being developed by a consortium led by Bridgend’s DST Innovations. This privately funded, ambitious project will now seek to combine tidal lagoon power with floating solar in an off-grid scheme that will deliver electricity to a co-located battery manufacturing facility, a data centre, and more than 5,000 local homes.

“The idea is that all of the power offtake would happen within the lagoon itself,” said Sheppard. “They’re going through the process of getting their project consented and approved. They’ve established a collaboration agreement with Swansea Council, and that’s looking like the most promising lagoon at the moment.”

Swansea's proposed Blue Eden project will include a 9.5km long tidal lagoon that uses underwater turbines to generate 320 megawatts of renewable energy

At the far end of the Welsh coast, away from the Celtic Sea, tidal stream energy has also just received a major shot in the arm. In December 2021, the Morlais tidal energy scheme was granted initial consent by the Welsh government, paving the way for a 35km2 plug-and-play demonstration zone off the coast of Holyhead, Anglesey. Connected to the UK grid, Morlais is set to be the biggest tidal stream demonstration site in the world, with the potential to deliver up to 240MW of predictable, dependable, green electricity. The site is due to come online in 2023/2024 and, according to Sheppard, will be a massive step forward for tidal stream energy, helping to bridge the gap between R&D and full deployment.

“It’s a really important step in bringing down the cost of energy for tidal,” he said. “You have places like EMEC (European Marine Energy Centre, Orkney) which are for testing the technology and seeing how it works in quite a high energy site...Morlais is sort of the next step after, so you should have already tested your technology, it should be mature. This is the fine-tuning, learning by doing, bringing down costs to make tidal competitive. The reason offshore wind is so cheap now is because it’s had that level of investment in support from UK government. We’ve now got that initial investment from UK government, so if tidal stream projects can deliver and can show a clear cost reduction curve, this is now a pathway to commercialisation for that industry.”

One of the huge benefits of incorporating tidal into the renewables mix is its dependability. Both tidal stream and lagoons can deliver baseload power at various, predictable times of the day, smoothing out the peaks and troughs of more sporadic renewables like wind. And given the sheer scale of the potential for UK tidal, it’s a technology the country can ill afford to ignore as the twin goals of energy security and net zero loom large. “I think over half of Europe’s tidal resources are in UK waters,” said Sheppard. “So it’s indigenous and we are leading the world in terms of this technology development as well.”

While not as predictable as tidal, wave energy is yet another huge resource that the Celtic Sea has in spades, with North Atlantic weather systems chasing in towards Land’s End and up into the Bristol Channel. Swansea-based Marine Power Systems (MPS) is currently developing a flexible floating platform that can not only host its own proprietary wave energy converter (WEC), but which can also serve as a FLOW base for third party turbines.

Combining wave and wind energy in a single floating platform seems a logical step, especially given the more aggressive conditions where FLOW is likely to be sited. MPS has been strongly backed by the Welsh government and very much has an eye on the Celtic Sea, but its immediate attention is on field testing its dual-energy platform under the right conditions, and for that it has had to look to Spain. “There’s no site in Wales or the UK that’s got the right depth for a floating offshore wind test and demonstration zone with a grid connection that’s fully consented,” explained Gareth Stockman, chief executive at Marine Power Systems. “So the Spanish project is a plug and play. You pay and you get the site and you can go over and test it.”

MPS has secured its Spanish berth for two years, but the company expects the technology to have proven its mettle within six to 12 months. Although its tetrahedral PelaFlex platform can operate as a base for wave or wind individually, its dual-energy mode – with both a turbine and two of MPS’s PelaGen wave converters attached – is undoubtedly its most eye-catching configuration. According to Stockman, bar a marginal additional cost to the structure, combining the two types of generation in one platform is all upside.

“It’s all mainly advantages, there’s no disadvantages,” he said. “In hostile energetic sites like off the west of Ireland or the west of Wales, although you’re putting a bit more cost into the structure so it can support the WEC , obviously you’re having another source of power...and the cost of energy from a combined device will be less because you’re capturing dual sources of energy on one platform, even if the platform does cost a little bit more than purely an offshore wind platform.”

Adding wave into the energy mix also delivers an element of grid balancing, as even though it is the wind that drives the  waves, the two are often desynchronised. Wind energy generally comes first, followed by the corresponding wave energy passing through hours or days later, providing a smoothing effect for the grid.

Given the UK’s profusion of  both wind and wave resources, there are no shortage of potential partners for MPS at home. Sitting right on its doorstep, the Celtic Sea is an obvious target, but the company is also engaged with developers around the world as well as others in the UK, not least in Scotland, where the recent Scotwind auction saw 15GW committed exclusively to floating offshore wind. “We’re engaged with 90 per cent of those farm owners,” said Stockman. “Here in the Celtic Sea, we’re engaged with everyone. There’s ambition of 4GW installed capacity by 2030 and we’re engaged with all the farm developers being down-selected to be the chosen providers.”

For now, Wales may be lagging slightly behind its Celtic cousin to the north, but if the true potential of the Celtic Sea can be unleashed – FLOW, tidal stream, lagoon and wave – it looks set to play an even more prominent role in the net zero pursuit.