The Greenlink Interconnector is a proposed HVDC transmission system between Ireland and Wales, UK. Image courtesy of Ikhlasul Amal.
The Greenlink Interconnector will have the potential to supply electricity to approximately 380,000 homes. Image courtesy of zorori47.
The Greenlink Interconnector is estimated to cost approximately £400m (€450m). Image courtesy of Rob984.

The Greenlink Interconnector project is a proposed 320kV high-voltage direct current (HVDC) power cable system between Ireland and Wales to interconnect the electricity networks of Ireland and Great Britain.

The 200km-long subsea and underground power transmission link across the Irish Sea is estimated to require approximately £400m ($530m) of private investment.

The project is being developed by Greenlink Interconnector, a joint venture of Element Power Holdings, a part of Hudson Sustainable Investments, and the private markets investment management firm Partners Group.

The Greenlink Interconnector has been recognised as a project of common interest (PCI) by the European Union, as it not only links the Irish grid with Great Britain but also provides onward connections to continental Europe.

The project is currently in the process of obtaining regulatory permits and licenses with a target to bring the interconnector into operations in 2023.

Upon commissioning, the bi-directional transmission system will be capable of transmitting 500MW of electricity which will be enough to power approximately 380,000 homes for a competitive price.

Greenlink Interconnector route and design

The Greenlink electricity interconnector project will connect EirGrid’s 220kV transmission substation at the Great Island, Wexford County, Ireland with National Grid’s 400kV transmission substation at Pembroke, Wales, UK, covering a total length of approximately 200km.

Both the substations will be interconnected by two 320kV high voltage direct current  (HVDC) cables.

The project also involves two converter stations incorporating the voltage source converter (VSC) technology, one near the Great Island substation, and the other near the Pembroke substation for the conversion of electricity from AC to DC and vice versa.

The VSC converter station requires small footprint of 1.85ha and it will include a converter hall, converter transformers, AC switchgear and busbars, harmonics filters, lightning towers, ancillary plant-like cooling bank and diesel generators, and a control building.

Onshore and offshore HVDC cables

The proposed Greenlink interconnector system will comprise two HVDC power cables and a fibre optic cable.

Approximately 160km of offshore HVDC cables will be buried in the seabed of the Irish Sea, while approximately 22km of underground onshore HVDC cables will be buried in a single trench at 850mm to connect the converter station to the substation.

The horizontal directional drill (HDD) method will be applied to install cables at the landfalls at both Baginbun Beach in Ireland and Freshwater West in Wales.

Project financing

The Greenlink Interconnector project is being co-financed by the EU through the Connecting Europe Facility (CEF).

The project received approval for funding of up to £4.2m ($5.65m) and £3.2m ($4.2m) in the first and the second phase of CEF Energy Call for Proposals 2018.

Contractors involved

Mott MacDonald carried out technical advisory services on the project on behalf of Partners Group in June 2019. The contractual scope included the review of project development, design and procurement, and assessment of project costs.

Mott MacDonald also transferred knowledge of the UK interconnector cap and floor regulatory regime.

Intertek was contracted to provide total quality assurance solutions in marine route development, landfall identification, and initial environmental permits for the project in May 2018.

WSP was awarded the contract for providing final cost support, technical assessment for Ofgem and the Irish regulator Commission for Regulation of Utilities (CRU), and execution of the procurement process for the entire HVDC system in June 2018.

Greenlink interconnector project timeline

The subsea surveys for the project were undertaken in September 2018 while the public consultations were completed in 2019.

The project partners obtained the necessary onshore planning approvals from the Pembrokeshire Coast National Park Authority, Wales in July 2020