Urgent action needed to harness tidal power in Severn estuary, say experts

22 03 2025 | 11:56Jamie Grierson/The Guardian

Commission launched in 2022 says lagoon project, not full barrage, should be backed by UK and Welsh governments

Urgent action is needed to harness the UK’s potential for tidal range energy in the Severn estuary but smaller lagoon models should be pursued over a larger dam-like barrage, a panel of experts has said.

The Severn Estuary Commission said that harnessing the energy of the tides in the estuary could deliver predictable, renewable electricity that would work independent of weather conditions.

But it stopped short of recommending a full dam-like barrage across the estuary – an idea that has been floated for many years.

The commission’s chair, Dr Andrew Garrad, who recently received the Queen Elizabeth Prize for Engineering in recognition of his role in pioneering development the modern wind energy industry, said: “This last year has been an eye-opening experience for all of us on the commission, understanding the huge potential of this source of renewable energy and also the international environmental importance of the estuary. Indeed, what sets this commission aside from previous studies is the emphasis that it has placed on the environment.

“Electricity demand will increase with the widespread uptake of electric vehicles, electrification of heating, industry and proliferation of datacentres. We urgently need to get serious about how we can make use of our natural resources to meet this demand whilst also tackling our carbon emissions.

“Given the likely timelines for developing a project of this scale, we need to act now to ensure we can deliver the energy when it is needed and at the same time safeguard the environment.”

The commission is made up of nationally and internationally recognised engineers, financiers, scientists and other experts, and was launched by the Western Gateway “powerhouse”, a coalition of politicians, business and public sector leaders and academics covering an area stretching from Swansea to Swindon and straddling the Severn.

It was launched in 2022 as the Russian invasion of Ukraine forced the issue of energy security back on the agenda and for the past year has been engaging with hundreds of individuals and organisations to explore if it is now possible to harness the power of the UK’s largest tidal range after decades of proposals. The Severn estuary holds the largest share of the UK’s tidal range energy potential, estimated at 8 to 12 gigawatts, and could contribute up to 7% of the UK’s electricity needs.

Publishing its final recommendations on Wednesday, the commission said that, due to environmental impacts, legislative barriers and the impacts on ports and other commercial activities, at this stage the development of a large barrage in the Severn estuary should not be pursued.

However, it said a lagoon project – which functions similarly to a barrage but over a smaller body of water – offered a positive alternative and should be backed by the UK and Welsh governments.

The UK’s National Energy System Operator already predicts that tidal energy will need to play a part in any future energy system. The Severn estuary has one of the highest tidal ranges in the world and could provide the vast majority of the UK’s total tidal energy. However, it also remains of international environmental importance.

The recommendations have already received the backing of the Welsh government.

Sarah Williams-Gardener, chair of the Western Gateway, said: “We need urgent action to make the most of this opportunity. A lagoon project would not only deliver predictable renewable energy, it could also add up to £12bn GVA (gross value added) to the UK economy and 220,000 job years in the construction phase.

Cover photo:  Avonmouth docks seen from Portishead, in the Severn estuary. The estuary could contribute up to 7% of the UK’s electricity needs. Photograph: John Bracegirdle/Alamy

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