The Swansea Bay Tidal Lagoon is a 320MW tidal power plant proposed to be developed in the Swansea Bay, in South-west Wales, UK.  It will be the first tidal lagoon and the biggest tidal power plant in the world.

Tidal Lagoon Power is planning to develop the project with an estimated investment of £1.3bn ($1.6bn).

The UK’s Department of Business, Energy and Industrial Strategy (BEIS) issued the planning consent the project in June 2015 which is set to expire in June 2020.

The UK government, however, decided not to provide financial support or subsidy to the project in June 2018.

Tidal Lagoon Power launched a £1.2 million fundraise in December 2019 to initiate preparatory construction works at the site so that it can secure the planning permission in perpetuity before its expiry.

The main works including the construction of the seawall, and the turbine and sluice gate housing block are expected to be started only after the project reaches financial close.

If built, the Swansea Bay Tidal Lagoon is estimated to generate 572GWh of electricity a year, upon commissioning. It is considered to be a pathfinder project which can be used as a blueprint for future large-scale tidal lagoon developments around the world.

Location and site details

The Swansea Bay Tidal Lagoon will be located off the coast of Swansea in Swansea Bay, South-west Wales, UK. It will be situated at the western end of the Severn Estuary.

The seawall will make landfall at the eastern edge of the new Swansea University Bay Campus and at the eastern side of the River Tawe. The lagoon will encompass approximately 11.5km2 of Swansea Bay where the tidal range is up to 9m.

Swansea Bay tidal lagoon project make-up

The length of the U-shaped seawall will be approximately 9.5km with the western portion measuring 2.7km and the eastern section stretching for approximately 6.8km. Both sections will comprise a road and a footway.

A low-voltage substation and the operation and maintenance facilities will be located on the western seawall.

The turbine and sluice gate housing structure will be approximately 410m-long and 67.5m-wide. It will house 16 variable speed hydro-turbines, associated electrical equipment, and 10 sluice gates. The aggregate installed capacity of the turbines will be up to 320MW.

The electricity generated by the turbines will be transmitted through an underground 275kV cable to the Baglan Bay substation which is connected to the National Electricity Transmission System (NETS).

The project plan also includes developing facilities related to sports, recreation, and mariculture in the lagoon. The seawall will be open to the public for various activities including walking, running, and cycling.

Tidal lagoon power plant operating principles

A tidal lagoon is an artificial lagoon made by constructing a seawall. The electric power is generated by harnessing the difference in water-level created by the seawall during flood and ebb currents.

The seawater will flow inside and outside the lagoon through the sluice gates during the flood and ebb currents. The difference in water levels between the lagoon and the sea will drive the turbines to generate electricity.

The seawall acts like a tidal barrage obstructing the flow of water from the sea to the lagoon. The sluice gates will open when a sufficient head is achieved and water flows through turbines.

During the flood current, which is an incoming tide, the water level inside the lagoon is lower than the sea. While during the ebb current, which is an outgoing tide, the water level inside the lagoon is higher than the sea.

In Swansea Bay Tidal Lagoon, the electricity will be generated both during the flood current and ebb current using bi-directional turbines. There will be four power generation cycles in a day. The tidal lagoon-based power generation is a predictable source of renewable energy, unlike wind and solar which are intermittent in nature.

The two prominent tidal power plants currently in operation globally are the 240MW La Rance tidal power plant in France and the 254MW- Sihwa Lake tidal power station in South Korea. Both La Rance and the Sihwa Lake facilities are based on the concept of the tidal barrage which is different from the tidal lagoon.

Swansea Bay Tidal Lagoon project financing

SIMEC Group, an international energy and commodities company, agreed to invest in the developer and operator of the Swansea Bay Tidal Lagoon in February 2016.  InfraRed Capital Partners and UK-based insurance firm Prudential also agreed to invest in the project earlier.

The UK government decided not to provide financial support to the Swansea Bay tidal lagoon project in June 2018 based on an assessment that the project was not affordable and the value for money requirements for consumers and public funds were not met.

The assessment concluded that the capital cost per unit of electricity of Swansea Bay tidal lagoon would be more than three times of the Hinkley Point C nuclear power station, and a £400m ($530m) offshore wind firm would have the same power output as the proposed £1.3bn ($1.6bn) Swansea Bay tidal lagoon facility.

Contractors involved

A consortium Andritz Hydro and General Electric (GE) was chosen as the preferred bidder to supply electromechanical equipment for the project in February 2015. The scope of the contract worth £300m ($400) included the supply of 16 bulb turbines.

Laing O’Rourke was selected as the preferred bidder for constructing the turbine and sluice gate block for £200m ($270m) in May 2015.

Atkins was hired to provide design and engineering support for the seawall as well as the turbine and sluice house structure of the project in August 2014.

Alun Griffiths was chosen for an ancillary civil engineering package worth £25m ($34m) for the public realm works involving the construction of seawall surface, roads, slipways, utilities, and landscaping in June 2015. Costain, an engineering solution provider, was awarded a contract to provide engineering solutions for the project in July 2013. The scope of the contract included making schedule for pre-construction and construction phases and developing construction methodology for civil engineering works.

LDA Design bagged a contract to provide master planning and landscape design services for the project in April 2013.

KGAL Consulting Engineers was hired as the mechanical and electrical (M&E) design specialist for the project in April 2013.