Snaking beneath the North Sea from the UK to Germany, the Tarchon interconnector promises to provide cheaper, greener and more secure energy by establishing a direct power link between the two countries’ energy markets.
The 1.4GW connection will be capable of powering up to 1.5m homes in either country. If one has a surplus of energy, it will be transferred by the 466-mile cable to help meet the power needs of the other.
Tarchon was among three new links to overseas markets greenlit by UK energy regulator Ofgem in November 2024. The UK currently has seven operational interconnectors, while two more, GreenLink to the Republic of Ireland, and NeuConnect to Germany, are being constructed.
Interconnectors help to alleviate the peaks and troughs of renewable power generation. They form a crucial component of the UK’s clean power plan, which sets a target for 95% of Britain’s electricity to come from clean sources by 2030, with the ultimate goal of reducing carbon emissions to net zero by 2050.
“Tarchon will help reduce CO2 emissions across the European region by between eight and 16m tons across the lifetime of the asset,” says project director Jonathan Wood MRICS. “One of the key reasons we are doing this is to make sure that we are utilising renewables most efficiently. But equally it will help to reduce consumer bills by allowing the import of cheaper electricity from one market to another.”
He brings considerable experience to the task, with a series of interconnector projects already under his belt including NeuConnect and IFA2 to France. “Working on those helped me understand my passion for delivery of large, complex projects, preferably with an international angle,” he says.
Such projects are extremely complex and challenging to deliver, however. The approvals process alone is a daunting prospect. Initial promoter and current minority investor Volta Partners sought a connection to the UK National Grid in 2019, and were awarded a link to the proposed East Anglia Connection Node. That made the project eligible to apply for approval under Ofgem’s ‘cap and floor’ regime, a mechanism which guarantees a baseline return for investors while capping excessive profits.
In 2022, Danish investment firm Copenhagen Infrastructure Partners bought a majority shareholding in Tarchon. An application for the first stage of approval was submitted to Ofgem, setting out all the characteristics of the project including the technology choices, the connection locations in both countries, the anticipated route, procurement strategies, costs, and timescale.
After approval was granted two years later, the door was open for Tarchon to be granted nationally significant infrastructure status in the UK. It is also designated a ‘project of mutual interest’ within the European region. That status is helpful because it requires consenting authorities to prioritise the project in their processes, says Wood. But it also increases the pressure on the Tarchon team, which consists of 20 people plus around 40 personnel from external consultants.
“It means we need to complete the consenting processes in all jurisdictions in alignment with one another,” Wood explains. “We have to do the onshore and offshore surveys, develop our permit submissions, get land options and easements in place and have that determined within a three-and-a-half-year period.”
“It’s vital that we get around kitchen tables, not hide behind keyboards. We need to be proactive and transparent” Ed Higson MRICS, Dalcour Maclaren
Image composition courtesy of Tarchon
Subsea cables in international waters
The Tarchon cable will pass through the national waters of three countries: the UK, the Netherlands, and Germany. At both ends a converter station will be built to convert alternating current into direct current for more efficient transmission, then back again. Each building will be approximately 250m2, and up to 26m high, requiring around 10ha of land. In the UK, the Tarchon team is investigating potential converter station sites close to the connection node for feasibility and carrying out consultation.
“It means we need to complete the consenting processes in all jurisdictions in alignment with one another,” Wood explains. “We have to do the onshore and offshore surveys, develop our permit submissions, get land options and easements in place and have that determined within a three-and-a-half-year period.”
Underground cabling will conduct power onshore to the converter stations and then to the nodes where the interconnector plugs into the national grid in each country. Some 75 miles of onshore cabling will be required in Germany. In the UK, the journey to the grid from its proposed landfall zone to the south of Harwich in Essex is much shorter at around 12 miles. Securing the rights over the land along its route will still require extensive negotiation with multiple landowners, however. That task has been entrusted to Ed Higson MRICS, a director at specialist infrastructure and utilities consultancy firm Dalcour Maclaren, and his team.
Landowners along the route include big estates, large agricultural businesses and small family farms. Dalcour Maclaren is aiming is to secure voluntary agreements where possible, only using compulsory purchase as a last resort. Good communication skills are essential because representatives of a potentially disruptive project are unlikely to be welcomed with open arms, admits Higson. “It’s vital that we get around kitchen tables, not hide behind keyboards. We need to be proactive and transparent, listen to their concerns, engage with them and show empathy”.
Ahead of negotiations, Dalcour Maclaren’s geomatics professionals have undertaken land referencing to identify, map and interrogate land interests and rights, while a broader team of surveyors pull together property cost estimates to support project budgets. Dalcour Maclaren will continue to work on the project into the delivery stage providing agricultural liaison officers to minimise impact, then completing easements and settling compensation claims.
A marine survey is planned for 2026, and securing permissions for the offshore route is even more complex. A subsea trench will be dug for the cable to be laid and then covered over using an enormous plough pulled behind a ship, or a high-pressure water jet depending on seabed conditions.
The route will pass through fisheries, shipping lanes, ports, and environmental protection sites, passing close to undersea assets including other interconnectors, fibre and electricity cables and pipelines. “We have tried to deal with that complexity by having people who are based in each jurisdiction, understand local regulations, and who can support us in building direct relationships with the authorities there,” says Wood.
“It will help to reduce consumer bills by allowing the import of cheaper electricity from one market to another” Jonathan Wood MRICS, Tarchon Interconnector
Image composition courtesy of Tarchon
Supply chain constraints
Final determination of all the necessary consents is anticipated in 2028 to 2029, after which delivery of the multi-billion-pound investment will take four or five years. Completion was originally targeted for 2030, but Wood explains that Ofgem has provided Tarchon and other “Window 3” interconnector projects with a later backstop date of the end of 2035. This is because of worsening supply chain constraints caused by intensifying demand in the HVDC (high-voltage direct current) market.
“It takes a blend of skills to establish a multidisciplinary team that is able to deliver these projects,” says Wood. “We’ve got a technical and engineering function, commercial and regulatory, health and safety, project management, consents and, of course, procurement.”
He expects to see the project through to fruition, by which time he will have committed a decade of his working life to it. “Projects like this get under your skin”, he says. Besides, he adds, it is important to have someone who can provide a consistent voice to stakeholders, whether in government or local communities.
“This is a project which requires so much commitment from so many different people. On a personal level, it would be a huge achievement to see it working,” he concludes. “But equally, all the people who work on it will have provided input to a project that helps achieve a more sustainable world. I hope that will be something that they feel was a worthwhile use of their time.”
