Ed Walker examines the installation of new electricity transmission infrastructure between Scotland and England
The UK and Scottish governments have both set legally binding targets to reach net-zero greenhouse gases by 2050 (2045 in Scotland). As we transition away from traditional fuel sources for powering vehicles and heating homes, successes in offshore wind and other sources of renewable and low-carbon generation are gaining much attention – but how else is our energy system evolving?
The UK is one of the world’s largest offshore wind markets, with over 10GW of installed capacity. In August, the government gave The Crown Estate the go-ahead to progress with the next steps in its Offshore Wind Round 4 plan, a leasing opportunity that could unlock up to 7GW of low-carbon energy.
In 2022 we also saw Crown Estate Scotland announce the winners from its first leasing round for Offshore Wind – ‘ScotWind’; alongside 25 GW of potential generation, this included specific provisions for floating offshore wind. ScotWind will soon be joined by further initiatives under the Innovation and Targeted Oil and Gas scheme – a leasing round focusing on projects to reduce oil and gas production emissions.
“We engaged with local communities and undertook stakeholder engagement to understand concerns”
Electricity generated through renewable and low-carbon technology in Scotland is growing, but there is a need to deliver green energy to other parts of the UK, to aid the decarbonisation of its energy system.
New energy links
Two overhead transmission lines and one subsea link currently carry substantial volumes of electricity between Scotland and the rest of Britain. The subsea link, Western Link, is 420km long, connecting the west coast of Scotland with Wales and providing more than 2.2GW of inter-connection capacity. Developed by ScottishPower (SP) Transmission and National Grid Electricity Transmission (NGET), it can transfer enough renewable electricity to supply more than two million homes. With renewable energy growing in Scotland, what is next?
In 2022, NGET and SP Transmission applied for consents for Eastern Link 1 (EL1), which will transport electricity between East Lothian and County Durham or vice-versa. Meanwhile,
NGET and Scottish and Southern Electricity Networks (SSEN Transmission) submitted applications for a second link, Eastern Green Link 2 (EGL2), between Aberdeenshire and East Yorkshire, which will carry enough electricity to power more than two million homes. These are the first of four proposed new high voltage direct current (HVDC) links between Scotland and England.
In 2022, UK energy market regulator Ofgem approved the Final Needs Case for both projects, subject to consents.
In doing so, it confirmed that, having considered consultation responses and having acknowledged the projected increase in renewable energy generation, “there remains a need for both links.”
EL1 and EGL2 broadly comprise the same onshore components at either end – a converter station, underground cables and other infrastructure to link to the existing electricity transmission network, connected by subsea HVDC cables.
Eastern Link 1
Marine length: Approximately 176km
Scottish landfall: Thorntonloch Beach, East Lothian
English landfall: Seaham, County Durham
Estimated programme: Commissioning, testing and operation from 2027
Eastern Green Link 2
Marine length: Approximately 436km
Scottish landfall: Sandford Bay, Aberdeenshire
English landfall: Fraisthorpe Sands, near Bridlington, East Riding of Yorkshire
Estimated programme: Commissioning, testing and operation from 2029
Taking the example of EGL2, how are the cables installed in the marine environment? At both the Scottish and English ends of EGL2, locations have been identified along the Aberdeenshire and Yorkshire coastline, called ‘landfalls’. There are two main ways to landfall subsea cables – horizontal directional drilling (HDD) or open cutting. HDD is a trenchless technology, avoiding the intertidal zone and thus direct interactions with the foreshore. NGET and SSEN Transmission intend to adopt HDD technology at both landfalls, reducing impacts on coastal environments.
EGL2, including its submarine section, will consist of two single-core HVDC cables; a corridor between the landfalls has been identified in which these can be installed. Each cable will comprise an electrical core of copper or aluminium and insulation, surrounded by lead alloy and polyethylene sheaths to protect it from moisture and physical damage, then steel armour wires and outer serving.
A fibre optic cable will run alongside for monitoring and communication.
The installation process will include:
- Pre-installation surveys to inform detailed cable engineering and installation approaches
- Route preparation, including the clearance of debris and material that may impede installation
- Cable installation using a range of equipment, including cable trenching ploughs, jet trenchers, mechanical trenchers and mass-flow excavation tools. The cables will be laid and trenched simultaneously (below left), or laid and then trenched separately (below right)
- Additional protection – the primary protection for the cables is to trench along most of the route. Where this cannot be done, external protection (such as rock berms) will be deployed.
A responsible approach
NGET and SSEN Transmission have considered a range of environmental, commercial, technical and human criteria to define cable routes that are the best on-balance solutions. However, how will the cables interact with the marine environment – and how will they be managed? Sean Stokoe, NGET senior project manager (consents), and Matthew Kinmond, NGET consents manager, provide more details: “A huge amount of work goes into the staged approach of developing our projects up to consent submission. This includes a comprehensive suite of seabed surveys, extensive stakeholder engagement, robust assessments and systematic design work.
”However, this doesn’t stop once the consent application is submitted.
If we get consent, and once we appoint installation contractors, further work is undertaken to refine the detailed design of our projects to discharge consent conditions. This is achieved through further targeted surveys of the seabed we plan to work in, the development of detailed installation methodologies and protocols in consultation with key statutory bodies, and the finalisation of route design, micro-siting routes to avoid the most sensitive receptors where possible.”
EL1 and EGL2 are clearly essential to a low-carbon future – but how will two such complex projects be delivered successfully? Barry Hughes, Eastern
Link development and delivery lead at ScottishPower Energy Networks, shares his thoughts: “The Eastern Link project will be a key component in ensuring energy generated throughout the UK and in particular Scotland’s East coast can be used in the most efficient way possible.
It also provides a strong link between Scotland and England, providing additional flexibility and stability for the UK’s transmission network.
“These links are critical to delivering UK and Scottish government renewable targets and reducing our dependence on volatile global wholesale gas markets”
“We have also engaged with local communities and undertaken stakeholder engagement to understand local and regional concerns to allow us to develop our plans pre-construction to maximise advocacy and understanding. We take our commitment to the local area seriously and are keen to maintain good relationships throughout the lifecycle of the project. Eastern Link is a huge undertaking with significant investment and considerable operations involved, but the delivery of a project of this size and scale will make a significant contribution to net zero targets and enabling a sustainable future for all.”
Kenny Nicolson, lead project manager at SSEN Transmission, has this to say: “These links are critical to our net-zero ambitions, delivering UK and Scottish government renewable targets and reducing our dependence on and price exposure to volatile global wholesale gas markets by supporting home-grown, affordable low-carbon electricity generation. But we also recognise we have an obligation to deliver these links responsibly, minimising and mitigating impacts on the environment and other users of the sea, where we need to work together to coexist in harmony. We also need to work to minimise and mitigate impacts on coastal and inshore communities that play host to our infrastructure.
“As we edge closer to construction, we look forward to delivering this national infrastructure, which will support hundreds of skilled jobs throughout construction and thousands more throughout the economy.”
Ed Walker, MIEMA CEnv, is a principal environmental consultant working on a range of marine-power projects for global energy consultancy Xodus.