C2I 2017: The Swansea Bay Tidal Lagoon project

The Swansea Bay Tidal Lagoon project, which uses a breakwater wall to harness the power of the tides, is the first of its kind and could provide a scalable blueprint for adoption worldwide

The winner in the Energy, Efficiency and Sustainability category is a ground-breaking project that promises to be a world first and could help pave the way to a greener future in the UK and beyond. Swansea Bay Tidal Lagoon will use a 9.5km breakwater wall to harness the power of the tides, with which the west coast of the UK is particularly well endowed. The 4-5m height difference in water between high and low tides will be used to drive 16 hydro turbines, providing clean, reliable electricity for more than 120 years.

Project partners Tidal Lagoon Power (TLP), Atkins and LDA Design have worked together to develop new technologies to maximise energy efficiency and value for money. Prior to working with TLP, Atkins had collaborated on a research project for the concept design of a novel low-head tidal turbine specifically designed to work on both ebb and flood flows. Whereas existing tidal-power schemes such as La Rance Barrage in France and the Sihwa barrage in South Korea utilise around 20 per cent of the available potential tidal energy, Swansea is expected to achieve efficiency in excess of 50 per cent.

The 7.2m-diameter bidirectional turbines will sit in 70m-long draft tubes, housed within

the banks of the breakwall. With an installed capacity of 320MW, the lagoon will provide 530GWh of net power output annually, enough to provide clean energy for over 155,000 homes. According to the developers, the project will result in 236,000 tonnes of carbon savings during each year of operation.

“The collaboration with Tidal Lagoon Power, LDA Design and others has resulted in a truly innovative project. Swansea Bay Tidal Lagoon will be the first project of its kind in the world,” said Atkins practice director Richard Schunter.

“This project will make a positive difference to people’s lives in the UK in a clean, sustainable and responsible way. As designers and engineers, these are things that excite us, and everyone involved in this project should be rightfully very pleased and proud of being part of the team.”

Construction of the facility is predicted to directly sustain over 2,200 jobs, and two new manufacturing sites are set to be located in Wales for the build. One of these will focus on machining and pre-assembly of turbines, while the second will deal with heavy fabrication of steel components. It’s estimated that 100,000 tonnes of steel will be used during construction, the bulk of which will come from the UK.

Central to the overall design of the lagoon is the breakwater, which Atkins worked on as part of an integrated and collaborative technical team. One of the fundamental challenges was to produce a commercially workable design that was sufficiently watertight. Innovation came in the form of a sand core rather than the rockfill used in traditional breakwater construction. However, the consistency of the sand is crucial: too fine and it gets washed out by the difference in water pressure; too coarse and the flow of water would reduce the head difference, leading to the loss of available power.

As luck would have it, a site investigation of the bay revealed that suitable sand deposits were available and could be dredged from within the circumference of the lagoon itself to create the breakwater’s core. Compared to using imported rockfill, local material reduces the capital cost, as well as providing the lower permeability that will enhance the overall efficiency of the lagoon.

As well as enabling the power of the tides to be harnessed, the lagoon is intended to be used as a community amenity. The seawall itself will be open to the public for exercise and will feature open space that includes a beach and rock pools. Meanwhile, the lagoon will be available for leisure activities and watersports such as rowing, sailing and canoeing.

According to TLP, there are already preliminary plans to stage a triathlon event in and around the lagoon, and 100,000 tourists are projected to visit the site each year.

“What’s brilliant about this project is that it’s not only about sustainable, next-generation energy, which is of course vital. It’s also about creating a lasting legacy for Swansea and Wales,” said Alister Kratt, board director at LDA Design.

“By putting people first, we can deliver infrastructure that works for everyone and that makes the most of opportunities to create great places where people belong.”

Conservation is also a key pillar of the proposal. There are plans for new salt marshes, as well as a lobster and oyster hatchery that will support the reintroduction of the region’s native oyster. The developers claim that the project will also protect against coastal erosion and flooding, and the design has been carried out to make allowances for future changes in sea levels.

Perhaps most importantly, Swansea Bay Tidal Lagoon can be a pathfinder project to demonstrate that the technology is ready for widespread adoption. If successful, it will provide a scalable blueprint that can be applied at various other sites across the UK, and at sites around the world where suitable tidal ranges exist. Larger lagoons would not only benefit from economies of scale; they would also have the potential to generate exponentially more power.

Just up the road in Cardiff, for example, plans are already under way for a lagoon with a breakwall roughly twice the length of the one that will be built in Swansea. However, the Cardiff lagoon would produce around 10 times the amount of electricity. Other lagoons are planned in the Severn Estuary, North Wales and Cumbria, and in total could amount to 8 per cent of the UK’s electricity needs. What’s more, the dispersion of the sites provides a geographical solution to the natural intermittency of tidal ebb and flow.

Further afield, opportunities for the technology have been identified in France, Mexico, Canada and India, and academic studies have identified over 300GW of potential tidal range capacity globally. It’s a project with the capacity to have a major impact on energy provision around the globe for decades to come.