Tidal lagoon hydropower project
The Tidal Lagoon Swansea Bay is a proposed tidal lagoon hydropower project at Swansea Port, being developed by a special purpose vehicle (SPV) company named Tidal Lagoon (Swansea Bay) (TLSB). The project received planning consent from the Department of Energy and Climate Change (DECC) in June 2015. It will be one of the world’s biggest tidal power plants.
The facility will use the ebb and flow of the sea tide to generate electricity. The renewable project will have an installed capacity of 320MW and a net annual output of 495GWh. The designed nominal rated capacity of the plant is 240MW.
The overall investment in the project is estimated to be £1bn ($1.5bn approximately). Construction works are expected to start in the second half of 2016 and take approximately five years. Connection to the national grid is expected to be achieved in 2018.
The project will primarily involve the construction of a breakwater wall or seawall, a concrete turbine housing unit, sluices, a visitor centre and ancillary onshore amenities.
The Glendoe Hydroelectric Power Plant is located at the western end of the Monadhliath mountains in the east of Fort Augustus in Scotland.
The project is expected to generate approximately 1,900 full-time equivalent (FTE) jobs during the peak construction phase and 181 FTE jobs during its operational phase.
The output from the project will be sufficient to serve approximately 155,000 homes in Swansea, which is equivalent to 90% of the city’s annual domestic electricity use. The plant will also offset 236,000t of CO₂ emissions a year over its designed operational life of approximately 120 years.
The project will provide visitor facilities as well as other educational and recreational facilities, which are expected to attract approximately 70,000 to 100,000 visitors a year. The project’s breakwater will also serve as a flood protection structure for buildings located near the lagoon.
The project site at Swansea Port is located approximately 2.2km southeast of the city centre. The site, located within the Severn estuary, was chosen due to the presence of a tidal range of up to 10.5m, a shallow seabed gradient that reduces the height of the proposed lagoon seawall and its close proximity to highly-populated areas, which reduces energy loss during electricity transmission.
A tidal lagoon hydropower plant produces electricity by harnessing the seawater level during tides. The seawater is first restricted from entering the man-made lagoon for approximately 2.5 hours during high-tides, which creates a difference in water levels between the sea and the lagoon, known as head.
The water is allowed to flow into the lagoon via the sluice gates, when a sufficient head height is achieved, thus feeding the turbines to generate electricity. The process is reversed, and the water is prevented from leaving the lagoon until there is sufficient head to further drive the bi-directional turbines.
The project involves the construction of a U-shaped breakwater wall, between the dredged channels of the Tawe and Neath rivers. It will stretch approximately 9.5km-long, thereby enclosing a tidal area of approximately 11.5km². Enclosing the Swansea bay, the wall will have its western landfall on the eastern side of the River Tawe adjacent to Swansea Port, whereas the eastern landfall will be located on the eastern end of the new Swansea University Bay Campus (SUBC).
The sea wall will have a visibility of 12m at low water and 3.5m at high. It will be constructed using dredged sandy materials, filled in long geotextile casings known as Geotubes that are 5m in diameter. The wall’s outer structure will be reinforced with layers of both small and large rock armours. The construction of the breakwater will require approximately five million tonnes of rock.
The turbine house and sluice gates will be constructed southwest of the lagoon, and the turbines will be mounted on concrete caissons in a single section. The turbine house will be equipped with 16 Kaplan bulb turbines that have an installed capacity of 20MW and measure 7.35m in diameter each. The tidal lagoon will be capable of generating baseload electricity for 14 to 16 hours a day, by generating power from each of the flood and ebb tides four times a day.
A three-storey offshore building housing the operations and maintenance and visitors facilities will also be constructed adjacent to the turbine house. A 4,000m² two-storey building will also be constructed on the site of the western landfall for further operations and maintenance requirements and an information wall and viewing platform will be constructed at the eastern landfall site.
The electrical output from the project will be conveyed to the national grid via the existing Baglan Bay substation using underground cables.
Good Energy has a stake in the project, which gives the company the right to purchase 10% of the electricity generated by the facility. Negotiations with more probable power purchasers are in progress.
The turbines will be supplied by a consortium of Andritz Hydro and General Electric under a contract worth €400m ($455m approximately). The consortium will also manage the operations and maintenance of the turbines and power generation facilities for the initial five years.
The turbine house will be constructed by Laing O’Rourke under a contract worth £200m ($307m approximately). The designer of the turbine house is Arup, the marine works will be performed by China Harbour Engineering Company (CHEC) under a contract worth £300m ($460m approximately), and the ancillary construction works will be performed by Griffiths.
LDA Design is the master planner for the project, while project management support is being provided by Costain. The client’s engineer is Atkins, the environmental consultant is Sustainable Direction and the engineering advisors are KGAL Consulting Engineers and Mott MacDonald.
Hydropower Engineering is the consultant advisor for the project and Infrared Capital Partners, and Prudential are the equity investors.
Other contractors involved with the project during the initial years of the planning phase were Alstom, Voith Hydro, Van Oord, Aecom, ABP Marine Environmental Research, Anatec, Cape Farewell, Clarke Sounders Associates Acoustics, Coastal Science, Cotswold Archaeology, DLA Piper, ESG, FaulknerBrowns Architects, FugroSeacore, Hyder Consulting, HR Wallingford, Intertek, Juice Architects, MPEcology, Seacams, SgurrEnergy, SoltysBrewsters, TenCate, Titan, TurnpennyHorsfield Associates, University of Leeds and University of Liverpool.
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