A turn in the tide

Materials World magazine
3 Sep 2015

The UK has approved construction of the world’s first tidal lagoon power plant, with the technology predicted to supply as much as 8% of the country’s energy. Khai Trung Le looks at the endorsement and disputes the project has garnered.

On 9 June 2015, Gloucester-based Tidal Lagoon Power (TLP) was awarded planning consent for its much-lauded Swansea Bay tidal lagoon plant. The £1bln project is touted as providing 495GWH of electricity every year, enough for around 150,000 homes.

The tidal lagoon plant is a straightforward design. A six-mile long wall will encapsulate a portion of Swansea’s coastline, creating a holding pool. As the tide rises, water levels will be higher outside the wall than within. Sluice gates open to let water in, turning the 16 turbines placed within the walls. As the tide falls, the lagoon will retain water until the lowest tide before again opening the sluice gates, turning the bi-directional turbines in the opposite direction. As Director of Engineering at the Institute of Mechanical Engineers Colin Brown remarked to the Guardian, ‘It’s a few turbines that we would use in an hydroelectric plant… it’s walls of rock and stone. I don’t think we’d need to split the atom here.’

However, the project has attracted vehement supporters and detractors in equal numbers, and has been surrounded with consistent controversy alongside extensive government endorsement.


Prior to being awarded, the Swansea Bay tidal lagoon long held the support of Chancellor George Osborne and former Energy Secretary Ed Davey, with the lagoon’s inclusion in the Conservative’s pre-election March 2015 Budget a boon for Davey, who is said to have persistently championed it despite initially being met with scepticism from Osborne and
the Treasury.

The Swansea Bay plant has also received the support of Friends of the Earth Cmyru (FoEC), with current Director Gareth Clubb lending the environmental campaigners’ support for the bay. ‘This project still has a few environmental hurdles to clear – such as the source of the rock to be used – but, provided these concerns can be managed and mitigated, tidal lagoons could make a significant contribution to a 100% renewably-powered UK.’ Clubb confirmed that FoEC has not conducted any recent investigations towards tidal lagoons beyond former energy campaigner Neil Crumpton’s 2004 paper A Severn barrage or tidal lagoons?, and stated that much of FoEC’s stance is defined by this early work, although concedes that ‘some of the information has, of course, now been superseded.’

The lagoon plant also saw fervent support from local industry, with the Swansea Bay Business Club president Bruce Roberts stating, ‘Every business that took part in a survey by our policy group saw the lagoon as a positive development that would bring economic and regenerative benefits to the bay region. Local companies saw significant economic benefits for the region from major schemes like the tidal lagoon.’

It’s a view shared by Simon Hamlyn, CEO of the British Hydropower Association, who remarks, ‘One of the things I find very appealing about the Swansea Bay project is the immediate value. They’ve thought very sensibly about how it fits in with the current environment and becomes an attraction to people in Swansea. They’ve thought about the sensibilities of it, not just said “let’s put a big lagoon here and generate lots of electricity”, but about how it exists within the community.’

Hamlyn enthuses on the future significance of the lagoon plant, noting, ‘I think it is very timely that we have an opportunity to support a project such as this one. We have always been in favour of harnessing all forms of energy through water power, and tidal lagoons are no different. Once we’re over this initial hurdle of getting the first project in place, there is an opportunity for more tidal lagoons. With a lifespan of 120 years, there are not many other forms of energy that have that kind of longevity.’


The Swansea Bay tidal lagoon plant is not without its detractors, among the most vocal being former Neath MP Peter Hain and Telegraph columnist Christopher Booker, who have taken umbrage on a number of issues, with the most prevalent being the cost of energy.

Energy from the lagoon will initially be priced at £168/MWh. Not only is that more expensive than offshore wind, widely considered to be one of the most expensive sources of renewable energy, but it is three times the price of wholesale electricity. TLP has claimed that, throughout the expected 120-year lifespan of the lagoon and through the establishment of multiple lagoon plants, this will decrease substantially.

Through the TLP website, Shorrock stated, ‘Economies of scale bring immediate advantages. A second lagoon will require a lower level of support than offshore wind, for a renewable power supply that is both long-lived and certain. A third lagoon will be competitive with the support received by new nuclear, but comes without the decommissioning costs and safety concerns.’

The energy cost is expected to be lowered to around £90–95/MWh following the construction of the third of six tidal lagoon plants planned, reaching parity with the current energy cost of the Hinkley Point C nuclear plant. Proposed sites for future Welesh lagoons include Colwyn Bay, where the lagoon is claimed to bring the benefit of flood defence, and Cardiff, planned to be around 5,700 hectares – three times the size of the Swansea plant.

Citizens Advice has also vehemently opposed the Swansea Bay lagoon plant on account of the energy cost, stating, ‘Putting aside the speculative nature of these cost reductions, even if it were guaranteed that they could be achieved, the best possible case put forward is that at some point in the future they could reach a cost level that can already be matched or beaten by other technology choices.’

Complainants are not restricted to the UK, with the Department of Energy and Climate Change confirming allegations have been made against the £300 million contract awarded to China Harbour Construction Company (CHCC), which has been selected to construct the lagoon wall. A challenge, which is yet to be disclosed, is believed to have come from shortlisted Belgian contractors concerning anti-competitive behaviour in the letting of the contract. Critics have also identified CHCC as an arm of China Communications Construction Company, which currently faces sanctions imposed by the World Bank on procuring certain contracts.

Future technology

Each of the 16 turbines will have a maximum output of 20MW, giving the Swansea Bay lagoon a combined maximum generating capacity of 320MW. Citizens Advice has also criticised the project on the grounds that it will not contribute to future innovation. ‘To ensure the most cost-effective use of the limited resources available to address climate change, this benefit from innovation funding should be tightly defined on the basis of two main criteria:

(a)     That the technology in question has scope for significant long-term global climate change mitigation, and

(b)     That the specific investments can make a material difference to global long-term reductions in cost of the technology.

'It is far from clear that the Swansea Bay tidal project meets either of these criteria. The project's developers have already stated that they do not anticipate any technology learning to come about as a result of the investment.'

However, Hamlyn challenged Citizens Advice’s despondency, stating, ‘Every turbine and every aspect of hydropower has undergone evolution over the past 100 years, and I don’t expect that process to stop. I think there will be development opportunities and ways in which it can innovate over the forthcoming years.

‘Once the scheme is up and operational in 2019, they will be able to assess the performance of all aspects of the scheme and start improving for the next one. That is the opportunity to see how development and innovation can be brought forward.’

TLP announced that the proposed Cardiff plant will be the UK’s first full-scale lagoon, and expect an annual output of 4–6TWh, enough to power every home in Wales.

Staying afloat

The UK Government remains committed to tidal lagoon energy, despite the array of issues that have consistently arisen, from disputes by Belgian contractors to local interests challenging the floated reopening of Cornwall’s Dean Quarry as the source of aggregate, or the lack of information surrounding the environmental impact of the Cardiff and Newport full-scale lagoon plants.

TLP declined to speak to Materials World, and while many reservations go unanswered, Hamlyn did not hesitate to endorse the future of tidal lagoon energy. ‘Having spoken to Mike Case (TLP Head of Turbines), my understanding was that the majority of people who have engaged in the process were in favour of the lagoon plant. Something that could create jobs, contribute to the country’s gross value added and supply power to 90% of homes in Swansea was always going to be quite popular.’

Predicted successive cost of energy per megawatt

Source: Patrick Mohr and Ali Lloyd, Pöyry, Levelised costs of power from tidal lagoons

Lagoon 1: £168/MWh

Lagoon 2: £130/MWh

Lagoon 3: £92/MW