Sink or swim for tidal energy after Swansea Bay lagoon proposal rejected

In late June this year, after seven long years of planning and development, the UK government finally rejected plans for a £1.3bn, 320MW tidal lagoon power scheme in Swansea Bay, South Wales.

Masterminded by UK-based Tidal Lagoon Power in partnership with turbine manufacturers GE and Andritz Hydro, as well as engineering consultancies Atkins and Arup and myriad UK suppliers, this project was to be the first of three tidal lagoons dotted across the South Wales coast, with more to follow around the UK.

Tidal Lagoon Power wanted to “build a new British industry”, an enthusiastic Welsh government had offered £200m to bolster development, but the final word from UK Business and Energy Secretary Greg Clark was clear.

“The project and proposed programme of lagoons do not meet the requirements for value for money... by 2050, the proposal that has been made could cost up to £20bn more to produce compared to generating that same electricity through a mix of offshore wind and nuclear,” he said. “When much cheaper alternatives exist, no project and no technology can proceed at any price.”

A negative government response was expected by many, but the outright rejection was difficult to swallow for most supporters. Welsh shadow MPs called for Welsh Secretary Alun Cairns to resign while Green Party leaders labelled the move a “government-induced environmental disaster”.

Tidal Lagoon Power (TLP) chief executive Mark Shorrock quickly responded, claiming the Secretary of State was “misinformed” over costs. And while the company declined to comment post-rejection, TLP director of engineering and construction Mike Unsworth had told E&T only days earlier: “If the government says no to Swansea Bay, then this is a standalone project and I do not see that as a no to future development of tidal range projects.

“Our next steps would be to look at alternative financing structures for Swansea but we are also developing two projects in France, and this will of course continue,” he said. “If the UK doesn’t run with this... other countries will.”

Does the rejection really pour cold water over a future UK tidal energy industry? While Clark was blunt on the government’s rejection of Swansea Bay, he cast out a line for future projects, saying his department is “in receipt of proposals from other promoters of tidal energy schemes which are said to have lower costs”.

Professor Roger Falconer, founder of the Hydro-environmental Research Centre at the University of Cardiff and vice president of the International Association for Coastal Reservoir Research, is hopeful.

Deeply disappointed with the recent Swansea Bay rejection he told E&T: “I regret that [Westminster] took so long to come to this decision, and it is a major setback for UK tidal energy projects but it is not the end by any means.

“We now need to move back to the drawing board and look at truly novel, cost-effective schemes for the future,” he adds.

Falconer is certain turbine development represents a first, huge opportunity for future British engineering. For Swansea Bay, TLP had selected Andritz Hydro’s state-of-the-art bi-directional, low head, Kaplan bulb hydro turbines that generate power on both ebb and flood tides, unlike the bulb turbines commonly used in conventional run-of-the-river hydro projects. Falconer is confident that, in time, further development will follow.

“I do think we need to get back to the fundamentals, and for, say, bi-directional flow [tidal energy schemes], we need to design turbines that are symmetrical, in that power is generated symmetrically and efficiently on the flow and ebb tides,” he says.

Falconer also points to novel structural marine works development under way in Asia. China Communications subsidiary CCCC First Harbor Consultants, for example, has already designed and built unconventional structures for breakwater projects at major Chinese ports and the Yangtze River estuary, including tooth-shaped embankments to alter water flows and sedimentation.

“These novel embankments considerably reduce [costly] rock requirements and are very attractive structures,” highlights the researcher. “In the longer-term I believe we will now also see many innovative schemes coming forward from the UK.”

One novel project that Falconer and other tidal energy players are watching avidly, comes from Professor Rod Rainey, an internationally-recognised authority in the field of hydrodynamic loading. Rainey has spent the lion’s share of his career working for Atkins Oil and Gas, specialising in the analysis of ships and offshore structures.

In a breakthrough that could prove instrumental for the future of UK tidal energy, he has devised a radically different tidal power scheme that could make the Severn Barrage a reality.

“This tidal barrage could be built across the Severn estuary... delivering as much power annually as Hinkley Point C, at a fraction of the cost,” he says.

The scheme would comprise a 15km line of 250 breast-shot water wheels with hydraulic transmission, stretching across the estuary. The original breast-shot water wheels date back to the Industrial Revolution and were used to extract as much power as possible from a stream. However, Rainey reckons his larger versions will be very different and have many advantages over the Kaplan turbines typically used in tidal energy set-ups, and also once destined for Swansea Bay.

For starters, breast-shot water wheels can use large blades to reduce flow velocity through the wheel, removing the need for the concrete, tapered entry and exit ducts typically fitted to Kaplan turbines. As a result, the entire barrage can be made from steel rather than concrete.

“La Rance in France is a working tidal barrage from 50 years ago and it’s concrete,” says Rainey. “But today steel, and steel fabrication, is so much cheaper, which is why I am proposing this lightweight steel barrage.” What’s more, thanks to slow blade velocities, fish should be able to safely pass through the water wheel, rather than dicing with death when swimming through the speedier Kaplan turbines.

Living up to its name, this type of water wheel has a cradle or breast-shaped structure that sits on the water-bed, leaving very little clearance to the blades at the bottom of the wheel and forming an almost watertight seal. As a result, when the water wheel stops so does the flow of water through the wheel, and if its motor is reversed as part of combined operations, water can be pumped upstream to maintain tidal range, which reduces environmental impact.

To date, water-wheel fatigue calculations have been favourable and Rainey claims his lightweight 15km barrage will generate an annual average power of 4GW, some 35TWh every year, around twice as much as a nuclear power station. And following promising comparisons with offshore wind farms on steel used and power output, he is working with developers and soon hopes to construct a pilot scheme in Scotland.

“British government carried out a study of Severn estuary power around ten years ago now but didn’t consider these lightweight steel barrages that I am proposing,” he says. “But Swansea Bay has now been rejected and I am in correspondence with Welsh government and relevant parties, so maybe we will see more developments here in the next few months.

“I believe the UK tidal energy projects still have prospects if you can show they aren’t causing environmental damage and they are economic,” he adds.

Rainey isn’t the only tidal energy developer certain that tidal energy projects will power the UK, given time. Ecotricity founder Dale Vince has long held that tidal energy would be significantly cheaper to produce if sited entirely offshore.

Having joined forces with Tidal Electric, US, to develop two tidal lagoon projects in the Solway Firth between England and Scotland, the company has proposals that promise to generate as much electricity as the Swansea Bay lagoon but at half the cost to build.

In a similar vein, North Wales Tidal Energy (NWTE) is proposing a £7bn tidal lagoon scheme that, while not offshore, would provide coastal and flooding protection to a 31km stretch of the North Wales coastline, with huge economic ramifications.

Recent Welsh government figures indicate that more than £3.3bn of property and infrastructure is at risk here while the current shoreline management plan only protects about £1.7bn of this property. NWTE’s tidal lagoon could change this. “As things stand the [flood protection] costs will fall to Welsh government and local authorities and these will run to many hundreds of millions of pounds,” says NWTE chairman Henry Dixon. “We can reduce that public cost... and studies with Wrexham Glyndwr University also indicate [the project] would create more than 20,000 jobs in North Wales.”

As part of the scheme, around 125 bi-directional turbines would provide an installed capacity of some 2.5 GW, generating more than 4TWh per year; enough to power 1.1 million homes or nearly 80 per cent of the homes in Wales.

“We’ve got the energy, the flood protection and the jobs; this could be transformational for the region,” says Dixon.

NWTE has already completed initial designs on the lagoon wall – including raising its 6.5m height by some two metres after 20 to 30 years to accommodate sea-level predictions – as well as turbines, sluices, locks, energy generation and coastal protection, and is now looking at environmental impact assessments. Of course, electricity costs are also at the forefront of Dixon’s mind.

While TLP’s final strike price for Swansea Bay was £92.50 per MWh over 35 years, Dixon says if NWTE’s project “doesn’t fly” at around £75 to £80 per MWh across some 30 years – between the strike prices for offshore wind and Hinkley Point – then development is not politically or financially acceptable. However, initial models indicate the target price is feasible, so now NWTE will continue to take its plans to government.

“The immediate impact of the government’s decision on Swansea Bay is negative as everyone sees a tidal lagoon being turned down, which is not good for investors or the general public,” says Dixon. “But we have been waiting for 18 months for a decision on Swansea Bay, which has delayed development, so at least we can now crack on. We are probably in a better place than we were [before Swansea Bay was rejected], as we now have a clear understanding of what government is looking for.”

Indeed, as the dust settles on the Swansea Bay lagoon rejection, and TLP turns its attention to new funding models and other tidal lagoon projects – within and outside of the UK – Dixon is not alone with his guarded optimism.

As the University of Cardiff’s Falconer puts it: “I think it will now take several years for the UK tidal industry to refocus but I do believe that for tidal energy structure and turbine design, Britain can lead the world.”