|A detail from the 3-D flythrough designed to show what the lagoon will look like.|
Public exhibitions are taking place at 18 locations around the Swansea Bay area from 4 July to 5 August.
The proposed tidal lagoon will have a rated capacity of 240MW, generating 400GWh net annual output, or enough electricity for approximately 121,000 homes, representing 70% of Swansea Bay’s annual domestic electricity use (Swansea, Neath & Port Talbot, 173k households); or about 9% of Wales’ annual domestic electricity use (based on 1,369k households).
The £650 million development will also host visitor facilities and other amenities including art, education, mariculture and sporting/recreational facilities.
The seawall is expected to be open to the public during daylight hours, though access will be controlled in extreme weather.
As part of the formal consultation for the proposed Development Consent Order (DCO) application by Tidal Lagoon (Swansea Bay) plc (TLSB), a new, virtual 3D programme has been prepared, which shows the lagoon in the context of Swansea Bay using an interactive fly-through.
Head of Planning for TLSB, Alex Herbert says: "This tool will help people to experience and understand the lagoon proposals as accurately as possible, so their feedback can help us to develop a truly world-class facility. All feedback from consultation will be taken into account as we move towards making a planning application later this year.”
Alister Kratt, Partner of LDA Design, said: “As the project develops, the opportunities that the masterplan provides should secure significant benefits for Swansea, including the completion of an attractive marine park which extends into the bay.”
As the project is an offshore electricity generating station of more than 100MW, it is considered to be a Nationally Significant Infrastructure Project (NSIP) under the Planning Act 2008, and so requires that a DCO is first granted by the Secretary of State for Energy and Climate Change via an application to the Planning Inspectorate (PINS).
Because it is located in Welsh coastal waters, it also requires a marine license to be granted via an application to the Marine Licensing Team of Natural Resources Wales (NRW) on behalf of the Welsh Government.
Additional consents may also be required from City & County of Swansea Council (CCSC) or Neath Port Talbot County Borough Council (NPTCBC) for elements of the Project which sit outside the NSIP and DCO.
How the plant will work
In order to control the flow of seawater to generate electricity, the Tidal Lagoon will be built by forming a 9.5km-long, U-shaped seawall running from Swansea Port out to sea before curving back to re-join land adjacent to Swansea University’s new Science and Innovation Campus (SAIC).
The seawall will have a sediment core held in place by a casing of sediment-filled geotextile tubes, known as Geotubes®.
The outside of the structure will be covered in rock armour of various sizes, depending on its level of exposure. The sand used to form the walls will be taken from within the lagoon footprint.
Rock armour will then be brought in by sea to provide protection. The top of the seawall will have an access road which will be used for operation and maintenance of the lagoon as well as for visitors.
In the south-western part of the seawall there will be a turbine/sluice gate housing structure. The housing structure will contain between 16 and 22 hydro turbines, which will be permanently underwater.
These turbines (which will be 7m-8m in diameter) will generate electricity on both the flood (in-coming) and ebb (out-going) tides. There will also be around 10 sluice gates, which will be underwater and able to let seawater in and out of the lagoon without going through the turbines, as required.
To generate electricity, as the sea starts to rise (flood tide) from low tide level, water is prevented from entering the lagoon for an average of 2 hours 5 minutes, and this creates a difference in water levels, known as ‘head’.
Once sufficient head has been reached, the water is allowed to flow into the lagoon through the turbines, turning the runner (which is shaped like a propeller) and generating electricity.
This process is repeated on the ebb tide, where the water is prevented from leaving the lagoon until there is sufficient head to start the process again.
Towards the end of the ebb or flood tide the sluice gates will be opened. This is to empty or fill the lagoon as quickly as possible before low or high tide level.
By doing this, it ensures that the lagoon water level is as close to the outside sea level as possible, before the tide starts to rise or fall again.
This is to maximise electricity generation and to keep the intertidal area as close as possible to that occurring naturally outside the lagoon.
An option to pump the seawater at the end of the tide is also being looked at to further equalise seawater levels.
This generation sequence will happen four times a day in total. The electricity generated from the lagoon will be transported to the nearest National Grid substation at Baglan by underground cables.
The cables will be laid in the seawall and then alongside existing roads/paths to the River Neath and onto the substation. To cross the River Neath, the cable will either be put through existing disused pipes or it will be drilled underneath the river.
Tidal Lagoon Power Limited
Tidal Lagoon Power Limited is privately funded and founded by Mark Shorrock, CEO, who has founded four companies including Wind Energy Ltd, a Scottish-based developer of wind farms. He grew Wind Energy Ltd into the largest independent developer of wind farms in the UK with over 650MW of wind farms moving through the planning process.
In 2006, Mark founded Low Carbon Investors, investment manager of the AIM listed Low Carbon Accelerator fund which he also founded. In 2008, he founded Low Carbon Solar Holdings, a private investment vehicle currently investing in solar power plants in Spain.
Prior to founding TLP, Mark was a founder of Low Carbon Solar which, in 2011, developed and funded the deployment of £70m of solar energy, totalling 28MW.
Tidal power globally
There are currently three large scale uni-directional tidal range plants in operation: Annapolis in the Bay of Fundy, Canada (30MW), La Rance in Brittany, France (240MW) and Sihwa in Korea (254MW).
There are also experimental tidal range energy projects being tested in Russia, UK, Australia, USA, Argentina, Canada, India, Korea and Mexico.
Potential sites for tidal range energy projects include the UK, France, Eastern Canada, Pacific coast of Russia, Korea, China, Mexico and Chile.
Other sites have been identified along the Patagonian coast of Argentina, Western Australia and Western India. In total, 70% of the Earth’s surface is ocean and 500,000km2 of that offers over four metres of tidal range.
Swansea Bay is one such place, and has been chosen as it offers the necessary conditions for building lagoons: the water must be shallow and the tidal range must be large.
The Severn Estuary holds the second highest tidal range in the world and Swansea Bay reaches a range of just over 10m.
As well as benefitting from this key characteristic, Swansea has a gently sloping seabed (suitable for this construction method) and proximity to a population centre, such that transmission losses are minimised from the electricity produced.