The Emerging Plans
The main components of the project will include subsea and underground cables together with new converter stations in both the UK and France.
The proposals are at an emerging stage and AQUIND is committed to engaging with the local community, local authorities, the Marine Management Organisation and all other interested parties before finalising them. For more information on the consultation, please click on News & Events.
Whilst dependent on the planning process and construction timescales, at present it is estimated that AQUIND Interconnector could supply power to the National Grid in 2022.
The Planning Process
Due to the nature of the project, the onshore and offshore elements of AQUIND Interconnector will be considered by separate bodies, including the Marine Management Organisation (MMO) and relevant Local Planning Authorities in the UK.
Similar applications will also be submitted to the relevant French planning authorities for the onshore and offshore elements located in France.
Before submitting these planning applications, AQUIND will carry out consultation on the proposals. This is the best time for local communities to influence the project.
Key Elements of AQUIND Interconnector
The offshore element of AQUIND Interconnector comprises four high-voltage DC subsea cables
that will cover the distance of approximately 190km between Eastney, near Portsmouth, and the Normandie coast near Dieppe in France. The cables, each at approximately 115-150mm in diameter, will be laid in pairs, or individually, together with fibreoptic data transmission cables of a much smaller diameter.
Where seabed conditions allow, the offshore subsea cables will be buried in trenches under the sea
floor such that sufficient protection is provided against ships’ anchors, fishing and natural hazards. Where trenches cannot be excavated, and at crossings of other cables, the subsea cables will be protected using alternative protection systems.
The subsea cable survey corridor has been selected and optimised based on best-practice guidelines through a review of potential landfall sites and a desk top study of seabed geology and existing constraints.
These have included fishing and shipping activity, other subsea cables, environmentally sensitive areas, aggregate extraction areas, offshore windfarms, known wrecks and the like. The marine survey has the been used to refine the preferred cable route within the survey corridor.
The Landing Point
The landing point is the location at which the subsea cables reach land, with subsequent connection to the respective converter stations being made via terrestrial underground cables.
In the UK, the proposed landing site is at Eastney, near Portsmouth. On the French side, the Interconnector’s landing point will be on the Normandie coast near Dieppe. The chosen landfall locations on both sides of the Channel have been shortlisted though an extensive optioneering process. This included detailed consideration of engineering and environmental issues, with particular consideration being given to environmental characteristics of the area including Special Protection Areas and Special Areas of Conservation.
Eastney was chosen as the preferred option, partly due to its relative proximity to the existing substation at Lovedean. Minimising the length of the underground cable route will significantly reduce the environmental impact and the disruption associated with its installation.
The Converter Station
Converter stations are required in both the UK and France to convert electricity from DC to AC. AC is used for transmitting electricity in the UK and France’s electricity grids, while DC is used for sending electricity along the subsea and underground cables because it is more efficient over large distances.
Lovedean in Hampshire was identified as the optimal location for the UK converter station, taking into account a number of factors, including the capacity of the existing network.
The converter station site will comprise a mix of buildings and outdoor electrical equipment, with the outdoor equipment being similar in nature to the equipment at the neighbouring Lovedean substation. The building roof line will vary in height, but will be approximately 22m at its peak. The design and layout of the converter station will be finalised in due course. It is anticipated that approximately 6-9 hectares of land will be procured for the converter stations in each country – this includes the areas designated for the converter station buildings, outdoor electrical equipment and any screening required.
Work is being carried out to understand any environmental constraints (including ecological, landscape and heritage features), and develop appropriate mitigation.
There are significant benefits in situating a converter station as close as possible to a substation. The AC cables used to connect HVDC converter stations to AC substations require more footprint and cause more disruption during the installation. AC cables also have higher transmission losses and pose other technical challenges.
The substation is where the flow of electricity will connect into the main power grid at both ends of the interconnector.
On the UK side, the interconnector will be routed to an existing substation in Lovedean, Hampshire, where it will connect to the National Grid Transmission System.
To determine the connection point, AQUIND commissioned National Grid to perform extensive studies, which showed that Lovedean substation is the optimal connection location from the South Coast of England.
Using an existing substation will further reduce the project’s environmental impact, making good use of existing facilities.