The interconnection of Ireland's electricity grid with mainland Europe moved a step closer to reality last week with the filing of a planning application by EirGrid for the new Celtic Interconnector with France. The €1 billion project involves the construction of a 575km interconnector that will run from east Cork to northeast Brittany and will be capable of carrying 700 megawatts of electricity, the equivalent of supplying power to about 450,000 homes.
The interconnector will improve the security of Ireland’s electricity supply by providing the country with its only direct energy connection to an EU member state.
"Part of EirGrid's role is to explore and develop opportunities to interconnect the electricity grid with those of our near neighbours," explains EirGrid chief infrastructure officer Michael Mahon. "We have already built an interconnector to Wales, the East-West Interconnector, and are now seeking planning permission from An Bord Pleanála to build one linking the Irish and French electricity grids – the Celtic Interconnector."
EirGrid has been working with its French equivalent Réseau de Transport d’Electricité on the project for the past 10 years. “The Celtic Interconnector is a flagship project for us,” says Mahon. “And it is one of the biggest infrastructure projects planned for the island.”
Due to its scale and importance the project is classified as a Strategic Infrastructure Development (SID). This means that An Bord Pleanála is the competent authority to decide on the planning application. A seven-week period of statutory public consultation will commence shortly and it is anticipated that the planning process may take up to 10 months to complete with a decision finalised in the first half of 2022.
“The filing of the application signals the end of the EirGrid consultation process on the project,” Mahon adds. “We have consulted comprehensively with communities in east Cork and other stakeholders. We listened to what the people told us and came up with a more acceptable proposal which avoided a few towns.”
The interconnector will comprise onshore and offshore elements, he adds. “It will comprise a 500km underground cable running from Brittany to Cork and a further 35km on land. We finalised the undersea route following lots of studies and surveys. In November 2020, we established that the best place to land the submarine electricity cable was at Claycastle Beach, near Youghal in east Cork. An underground cable will run inland on the national road and continue north of Midleton on local roads to the converter station.”
That convertor station will be built at Ballyadam, on part of an IDA-owned site, to the east of Carrigtwohill. The final connection will be by underground cable from Ballyadam to a substation on the national grid at Knockraha 10km away.
Among the key benefits of the interconnector is that it will allow power to flow in both directions. “When we have an excess of renewables on the system we can export that power to the European grid,” Mahon notes. “When we have a shortfall, we can import up to 700MW through the interconnector. One of the challenges we have as we increase the amount of renewables on the system is that there might be lots of wind one day and very little the next. We need back up when it drops off. That can be in the form of conventional gas generating plants, battery storage, or interconnectors. We also have the benefit of being able to export energy with high level of renewables in the system.”
The interconnector will ultimately support the achievement of national climate objectives by facilitating the increased amounts of renewable power on the system. "It may also help bring down the cost of electricity as the price of electricity in France is cheaper than in Ireland, " Mahon notes.
The continental connection also means EirGrid may be able to benefit from different peaks due to time and lifestyle differences. “Different peaks mean that power may be available at one end when it is most needed at the other,” Mahon adds.
The project is being co-funded by EirGrid and its French equivalent, with significant co-financing from the EU. In 2019, the project was awarded €530.7 million from the European Commission’s Connecting Europe Facility. The project also received EU funding at earlier study stages. “That will go a long way towards meeting the capital expenditure costs of the project,” says Mahon.
In deciding on the allocation of the funding the commission assessed which partner was likely to benefit most from the project. On that basis, EirGrid will receive about 65 per cent of the funding with the remainder going to France.
Three different permits are required for the project. Planning permission in Ireland and France and permission for the cable to pass through the UK economic zone. The UK permit will be sought next month while permission was granted for the French side of the project last December.
“We hope to have all permissions in place by the second quarter of next year,” says Mahon. “The procurement process for contractors in Ireland and France will start after that with a view to signing contracts in the second half of the year.”
The estimated delivery date for the project is mid to late 2026. “Work on laying the 5,000km of submarine cable can only be done in summer months when the weather allows. It will be buried under the seabed, not laid on it. That means digging a trench and covering it in water depths of up to 110 metres. It’s a huge technical challenge. That element of the project will be undertaken during 2024 and 2025.”
But Mahon is confident the challenge can be overcome. “It is a very technically complex project. It will be one of longest undersea cables anywhere in the world and it will be very challenging to deliver and operate. We are dealing with a lot of potential unknowns, but we will be working with some of the top companies in the world to deliver it.”