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Tag Archives: tidal barrages

Can tidal lagoons supply base-load power?

By Dave Elliott

The Swansea Lagoon didn’t feature in the Budget announcement, despite Labour’s John McDonnell saying “get on with it”, but with a decision still expected soon it does represent an intriguing idea, especially if it can be extended.  Charles Hendry’s review of Tidal Lagoons threw up some interesting possibilities and issues, including the idea that multiple projects could offer more nearly continuous output, as well as identifying some conflicts over what should be done. He noted that there were “some views that were mutually exclusive. Whilst some, especially in the financial and environmental communities, argue that a smaller tidal lagoon in Swansea Bay needs to be operational before a commitment can be made to larger projects on the most competitive terms; others, in the supply chain, academia and those pushing for faster action on climate change, argue that the cumulative economic and industrial benefits of a programme of tidal lagoons would inevitably be lost by such a delay”.

Hendry backed the latter view and proposed an initial trial go-ahead for the small 320 MW Swansea project – see my earlier post. But the aim was to see if further projects, including possibly cheaper, larger variants, might be worth pursuing and he also looked at some of the wider options that could open up.

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Renewables: observing the future

by Dave Elliott

In its business leader column on August 25th The Observer, said “If there is a body of opinion that states that wind farms and energy efficiency can fill the looming energy gap, then it is small and deeply unrepresentative”. www.theguardian.com/business/2013/aug/25/anger-fracking-cant-manage-without-gas

Germany is aiming to get at least 80% of its electricity from renewables by 2050, with overall energy demand cut by 50%, so the Observer seems to have it wildly wrong, certainly long term.  And in fact, far from being marginal, around 50 countries are already getting more than 60% of their electricity from renewables in the form of hydro, some of them near 100%. http://k.lenz.name/LB/?p=6525. Longer term, dozens of studies claim that renewables could supply 100% of the worlds electricity in many countries by around 2050. http://www.mng.org.uk/gh/scenarios.htm. That is what Denmark and New Zealand are aiming for and many others see renewable as their main future energy option- with China leading the way.

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Tidal energy and grid balancing

by Dave Elliott

There has been a renewed push for a Severn Tidal Barrage, but, as I have reported in earlier posts, many saw it as too big to fund and too invasive to allow. Dr Nicholas Yates from the National Oceanography Centre, who has carried out the research with a team at Liverpool University, has backed smaller barrages, which he suggested could supply 15% of UK electricity. He  told the BBC: ‘I think it’s unfortunate that attention for tidal range has tended to focus on the Severn, it’s the wrong place to start, it’s too big. Start small, it’s what the Danes did with wind – start small, learn quick and build up.’

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The Severn tidal barrage – better alternatives

By Dave Elliott

The report on the Severn tidal barrage from the Select Committee on Energy and Climate Change concluded that the proposal for a £25bn privately funded barrage from Hafren Power was not convincing and lacked detail. Hafren Power had “failed to overcome the serious environmental concerns that have been raised” and had “failed to reassure the ports industry that its business would continue to be viable with a barrage in place”. It went on, “while a tidal barrage could offer decarbonisation and energy security benefits, the Hafren Power project in its current form has not demonstrated sufficient value as a low-carbon energy source to override regional and environmental concerns. Alternative pathways exist to meeting our 2050 carbon targets.” It added that “alternative options for exploiting Severn tidal resources also exist” and it looked at some of them briefly, including the 250–350 MW Swansea Lagoon proposal, the 600 MW “Stepping Stones” Lagoon put forward by Parsons Brinckerhoff/Black & Veatch, and also Rupert Armstrong’s 6 GW Tidal Reef concept.

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Barrage sinks

It’s been a long running saga – over the years there have been many reports and studies on the idea of building a tidal barrage across the Severn Estuary. Most have said it was technically possible, but economically and environmentally challenging – although no final conclusion emerged, just more studies. The most recent study looked not just at the large Cardiff to Weston barrage idea, but also at other options for exploiting the large tidal range in the estuary – smaller barrages and tidal lagoons. However this time a decision emerged – basically they were all too expensive. The government’s ‘Severn Tidal Power Feasibility Study: Conclusions and Summary Report’ in October seems to have finished off tidal range projects in the UK, at least for the moment. Although it did say that the results for other locations around the UK might be different, it is hard to see how they could do better than the Severn – the best site by far in terms of tidal range. Given that most environmental groups strongly opposed large barrages, the government decision not to provide support did not lead to complaints from them about ‘ignoring green options’.

The main conclusions were pretty clear. ‘The Government has concluded that it does not see a strategic case to bring forward a tidal energy scheme in the Severn estuary at this time, but wishes to keep the option open for future consideration. The decision has been taken in the context of wider climate and energy goals, including consideration of the relative costs, benefits and impacts of a Severn tidal power scheme, as compared to other options for generating low carbon electricity. The Severn Tidal Power feasibility study showed that a tidal power scheme in the Estuary could cost in excess of £30bn, making it high cost and high risk in comparison to other ways of generating electricity.’

www.decc.gov.uk/severntidalpower

The report text is a little less abrupt. It says: ‘The Cardiff-Weston barrage is the largest scheme considered by the study to be potentially feasible and has the lowest cost of energy of any of the schemes studied. As such it offers the best value for money, despite its high capital cost which the study estimated to be £34.3 bn including correction for optimism bias. However this option would also have the greatest impact on habitats and bird populations and the estuary ports.’

It went on: ‘A lagoon across Bridgwater Bay (£17.7 bn estimated capital cost) is also considered potentially feasible, as is the smaller Shoots barrage (£7bn). The Bridgwater Bay lagoon could produce a substantial energy yield and has lower environmental impacts than barrage options. It also offers the larger net gains in terms of employment.’ By contrast: ‘The Beachley Barrage and Welsh Grounds Lagoon are no longer considered to be feasible. The estimated costs of these options have risen substantially on investigation over the course of the study’ It added ‘combinations of smaller schemes do not offer cost or energy yield advantages over a single larger scheme between Cardiff and Weston.’

It noted that, in addition, the study funded further work on three proposals using innovative and immature technologies (the Severn Embryonic Technologies study). It said: ‘Of these, a tidal bar and a spectral marine energy converter showed promise for future deployment within the Severn estuary – with potentially lower costs and environmental impacts than either lagoons or barrages. However, these proposals are a long way from technical maturity and have much higher risks than the more conventional schemes the study has considered. Much more work would be required to develop them to the point where they could be properly assessed.’

The spectral marine energy converter (SMEC), which makes use of the venturi effect, tapping off tidal flows to drive a separate generator, certainly looks interesting for the Severn and also, in smaller versions, elsewhere.

See www.verderg.com/.

DECC had previously indicated that if a scheme had been considered viable for the Severn, further consultation would have to continue up to maybe 2014 with construction then between 2015 to 2022, followed by operation perhaps in 2023. But all that is now wiped out. With DECC faced by spending cuts and the capital cost of the big barrage now put at £34.3 bn, it just wasn’t viable as a public project and, with the generation costs of the other options put higher, private-sector interest would be unlikely. So tidal range seems to been written out of the story for some while. Which leaves tidal currents – a much less invasive and rapidly developing approach, with, it is claimed (in the DECC 2050 Pathways study and the PIRC Offshore Valuation), a larger overall UK energy resource than offered by tidal range projects.

Tidal-current turbines can be much more flexible and modular – although there are site limitations. It seems that the Severn estuary isn’t suited to the pile driven support system needed. It does seem tragic to ignore the huge tidal energy potential of the Severn, so a tidal-range project or some other concept may yet be back there (e.g. SMEC), and also elsewhere (there are several proposals for smaller barrages (e.g for the Mersey, Duddon, Solway Firth) but maybe not a for while. A rearguard action is being fought by some of the original backers of the Severn Barrage (see www.corlanhafren.co.uk/. But it seems to be doomed in the current financial and political climate.

I’ll be looking at the tidal-stream options shortly. See also www.natta-renew.org for regular updates.

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