Shotton electricity converter station powers ahead

A new electricity converter station is being built at Shotton in Deeside, Wales as part of Eirgrid’s £560m East-West Interconnector project. The Shotton converter project will see a 261km cable that runs underground from County Meath in Ireland to Flintshire, coming ashore at Barkby beach in Prestatyn before travelling along the A548 to the converter site at Shotton.

The East-West Interconnecter is a major infrastructure initiative that comprises an electrical high-voltage direct current (HVDC) interconnector that has been developed between the Republic of Ireland and Great Britain. The development of the EWI forms the Republic of Ireland National Development Plan 2007-2013 to promote environmental sustainability targets, security of energy supply and competitively priced supply.

The new Shotton electricity converter is being built near the UPM paper mill on Deeside Industrial Park after plans for the build were approved by Flintshire County Council in April 2009. The converter station will convert electricity from alternating current (AC) to direct current (DC), making it suitable for transmission by underground and undersea cables. This will eventually produce enough power for 300,000 homes.

In order to strengthen the station’s structure, 690 supports are being driven deep into the ground at the site. The supports, known as Driven Cast In-Situ (DCIS) piles, each have the capacity to support 75 tonnes and will act as a foundation for the various areas of the station.

John Fitzgerald of Eirgrid, said: “The converter station forms an integral part of this project which will help to ensure there is enough power for homes, businesses and industry in both countries.

“Prior to our planning application, extensive consultations as well as comprehensive environmental assessments were undertaken to ensure the chosen site was feasible.”

An interesting aspect of the project is the recycling of the dust generated from the construction process. Welch Civils and Flintshire County Council are working in partnership to recycle more of the waste-generated dust in order to maintain the underground piping. Led by EirGrid, ABB, Welch Civils and Flintshire County Council, the £250,000 recycling scheme has created three full time jobs for the area.

In total, over half of the waste generated from the Shotton converter project is being recycled in order to rebuild the A458 road from Prestatyn to Shotton, which is currently being dug to lay the underground cables.

During the complex process, road surface is separated from waste. The waste is then sent through a mixer at a specialised recycling centre in Greenfield, Flintshire, where it is added to a stabiliser in order to produce a material that is suitable for filling the trenches that have been excavated.

Keith Williams from Flintshire County Council’s Environment Directorate said: “Such innovation and forward thinking is reducing the risk on the environment and does not compromise the quality of the reinstatement work. This is setting a precedent in the development of recycling techniques in the construction industry.”

Alan McHugh, EirGrid’s East-West Interconnector project manager, added: “We’re delighted with the levels of recycling being achieved on our project in North Wales. Recycling in this way makes sense on many levels and brings with it a number of benefits including a reduction in waste sent to harmful landfill sites, reductions in emissions from haulage and movement and a reduction in waste disposal costs.

“We are starting to recycle bituminous materials which will take us up to 68% of all materials recycled.”

East-West Interconnector

The £560m East-West Interconnector will create a strategic energy link between the UK and Ireland. Both Ireland Wales have some of the largest potential renewable energy generation resources in Europe and the interconnector will enable the full potential of these resources to be realised.

The EWI will have a total length of 261km, of which 186km is submarine cable 75km is subsoil cable. Two HDVC cables will be laid in close proximity to one another within a route corridor of 50m within the intertidal and a 500m corridor offshore. The two separate cables will come ashore at Rush North Beach, Co. Dublin, and then continue underground to Woodland in Co.Meath, allowing the transmission of 500MW of electrical power in either direction and forming an electrical loop between Ireland and Wales.

The flow of electric current within an electrical cable results in the production of electric and magnetic fields. Subsea electricity cables are designed to use either direct current (DC) or alternating current (AC), both of which emit EMF. A direct current (DC) cable has been selected for the East-West Interconnector project as a high-voltage alternating current (HVAC) would not be a suitable technology for the long distance subsea interconnection of unsynchronised grids. Long undersea cables have high capacitance, which has minimum effects when using DC but results in high losses with AC.

Depending on the seabed conditions, all of the cables are buried below the seabed surface in order to protect them from accidental damage (for instance trawling and anchors) or movement on the seabed. Where bedrock cannot be avoided, it may be necessary to lay the cable on the surface and cover it with suitable ‘armouring’ material, such as concrete block, rock protection or ‘mattresses’ over some of the route to protect the cable from scouring by tidal currents.

Energy security is important for Ireland as the country has a growing economy and therefore a reliable supply of high-quality power is needed to support it. Indeed, the Irish Government has recently published its energy policy White Paper, ‘Towards A Sustainable Energy Future for Ireland,’ which sets out the Government’s energy policy framework for 2007-2020, and the first strategic goal is: ‘Ensuring that Electricity Supply Consistently Meets Demand.’ It is expected that the EWI will increase the security of energy supply, as it will enable the Irish transmission system to import electricity from the superior British market when necessary.

The White Paper also sets the target of 33% of electricity being produced from renewable generation by 2020. The new EWI will not only allow Ireland to produce sufficient renewable energy domestically in order to meet this target, but will also allow electricity produced from renewable sources in Britain and further afield to access the grid.

In addition, the increased capacity to export and import energy is also hoped to lead to competition in the electricity market and ultimately help to reduce costs for electricity customers.

Eirgrid has a clearly defined role in the Irish electricity system: “To develop, maintain and operate a safe, secure, reliable, economical and efficient transmission system for the benefit of our customers; to deliver quality transmission and market services.”

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