House of Commons - A Severn Barrage? - Energy and Climate Change

A Severn Barrage? - Energy and Climate Change Contents

7 Barrage technology and alternatives

100. In this section, we consider Hafren Power's Very-Low-Head, bi-directional turbine design and examine the strengths and weakness of a fixed barrage structure with reference to international comparator sites. We also look at alternative approaches and proposals for harnessing the Severn resource, with some analysis of comparative socio-economic and environmental considerations. Finally, we look at approaches to the management of Bristol Channel's marine resources and Government's role in stimulating growth in the sector.

The Hafren Power barrage design

VERY-LOW-HEAD TURBINES

101. Hafren Power proposed to use a Very-Low-Head turbine design deploying two sets of contra-rotating blades, separated by a gap of 1.5m, which would spin simultaneously. Generation would be bi-directional; in other words, generating on both the ebb and flood tides. Hafren Power has indicated that they are considering purchase of the Intellectual Property Rights (IPR) for the Rolls-Royce/Atkins concept design produced for the Severn Tidal Power Feasibility Study.[225] Hafren Power stated that French company MJ2 Technologies have produced a fully operational VLH turbine, albeit on a smaller scale than the proposed Hafren turbine.[226] Regen SW and South West Marine Energy Park stated that such a turbine would be "of significant benefit" to the marine industry with the potential to "be applied across a range of projects in the UK and abroad".[227] Notwithstanding the further R&D required, it is promising to hear of progress in the development of the VLH turbine.

102. On the other hand, it is clear that engineering challenges remain and that the Hafren Power turbine is still some way off technological readiness. Commercial deployment of the turbine may be a more distant prospect, as Regen SW and South West Marine Energy Park outlined:

228

103. Vincent de Laleu (EDF Energy) confirmed that a 100% reversible turbine remained "a technical challenge" that would require "many years to develop".[229] Although Hafren Power has assured the Committee that it has included time for turbine testing and development in the project timescale, we doubt that the two years proposed will allow sufficient time for production of a novel turbine as well as the necessary independent verification and trials.

A FIXED BARRAGE

104. A fixed barrage which spans the length of the estuary is expected to maximise energy yield, due to the large area of water that it will impound. Professor Broyd (Engineering the Future) described the barrage option, compared to alternatives such as tidal lagoons and fences analysed during the Severn Tidal Power Feasibility Study, as "head and shoulders above the rest for any return on investment at all".[230] Hafren Power argued that the impounding an area of water of more than 500km² behind a relatively short impoundment wall (18km) is a highly efficient way of extracting maximum energy from the tidal range.[231] By contrast, lagoons would require a long perimeter wall to impound a relatively small area. Hafren Power claims that the proposed Swansea Bay Lagoon would only be able to provide one fourtieth of the energy of the barrage.[232] The "Stepping Stones" lagoon proposed by Parsons Brinckerhoff and Black & Veatch[233] would have a lower annual energy yield than the barrage (1.2 TWh/year), although capital costs are also much lower at £1.7billion.[234]

105. Nonetheless, a large fixed barrage structure, while arguably having the greatest generating capacity, also has its disadvantages. Specialist consultants HR Wallingford highlighted the construction risk involved in such a project:

235

106. Rupert Evans (Evans Engineering and Power Ltd) described the conventional barrage as an "elephant", due to the inability to modify or "future-proof" the structure. Mr Evans suggested that in contrast a tidal reef or fence structure would offer more flexibility and scope to adapt to technological advances or environmental concerns.[236] Friends of the Earth supported the need for "a degree of flexibility in deployment of infrastructure in the Severn", while some stakeholders maintained that barraging the estuary can never be acceptable due to damaging impacts on ports and wildlife, especially migratory fish.[237]

Tidal power facilities worldwide

107. Significant examples of tidal power facilities in operation worldwide include:

The 240 MW EDF tidal barrage facility at La Rance, currently the largest of its kind in Europe
The 254 MW tidal barrage in the Sihwa Lake in South Korea[238]
The 18MW Annapolis Royal Tidal Barrage in Canada, an ebb-only scheme designed as a pilot for a proposed larger facility in the Bay of Fundy which was not built due to environmental concerns[239]

108. As discussed in Chapter 4, these international sites do not necessarily provide useful environmental comparisons, however they do illustrate the feasibility of barrage technology. The bulb turbines at La Rance are "still performing well" almost fifty years after construction of the plant.[240] Although Vincent de Laleu (EDF Energy) was unwilling to disclose the precise cost of energy generated, it is widely acknowledged that the facility provides low-cost electricity.[241] In addition to the Sihwa Lake facility in South Korea, proposals have been submitted to build a larger 1.3 GW facility at Incheon Bay, although this project and further tidal projects in South Korea are reportedly on hold.[242] The Canadian experience offers less cause for optimism: problems associated with fish mortality, erosion and the upstream river have led to a decision not to develop further barrage schemes in the Bay of Fundy.[243] EDF Energy also points out that sites with the suitable tidal range conditions are "rare", which suggests that export potential for barrage technology is limited.[244]

An alternative approach?

109. Much of our written evidence drew attention to alternative technologies for harnessing the Severn's energy resources. Stakeholders argue that a smaller-scale, more incremental approach would allow tidal power technologies to be fully developed and tested, and environmental impacts assessed, before large-scale projects were attempted.[245] Black & Veatch and Parsons Brinckerhoff set out the arguments for a "step by step approach":

246

The Renewable Energy Association (REA) also expressed concerns about the "financial and environmental risks" of a large-scale barrage and advocated building a small barrage to begin with, "to assess the costs and monitor the environmental impact".[247]

110. The Regen SW and South West Marine Energy Park discussion paper, "Bristol Channel Energy - A Balanced Technology Approach", outlined an alternative vision for marine energy in the Severn. It claimed that a combination of tidal, wave and wind technologies could provide up to 14 GW of low-carbon electricity, obviating the need for a a "single mega-project which has major economic and environmental and impacts".[248] The paper also suggested that the focus on a single, "potentially divisive" barrage project is damaging for the marine industry and instead recommends "a more inclusive discussion".[249] Johnny Gowdy (Regen SW) explained in oral evidence that the "basis of the approach was to look holistically at all the potential energy sources in the Bristol Channel Area" and to "look to develop technologies as they became more mature and as they became more cost-effective."[250] Tidal resource modelling undertaken by the Energy Technologies Institute suggested that "the energy yield from a single large-scale Severn barrage could be achieved with a lower level of interaction and impacts through a combination of tidal energy extraction at a number of smaller, different sites."[251]

Other tidal power proposals

111. Proposals for tidal power facilities which have been presented to the Committee include:

A 600 MW tidal lagoon known as 'Stepping Stones' put forward by Parsons Brinckerhoff and Black & Veatch[252]. This would be a smaller scale project and is intended to embody a "step-by-step" approach which could potentially lead to larger projects. It would have a capital cost of £1.7 billion.[253]

Rupert Armstrong Evans (Evans Engineering and Power Ltd) outlined his proposal for a low-impact 6GW tidal 'reef' between Aberthaw in South Wales and Minehead in Somerset.

Tidal Lagoon Power Ltd have submitted a scoping report to the Planning Inspectorate for a 250-350 MW tidal lagoon in Swansea Bay with an estimated annual output of 400,000 MWh/year.[254] The company vision is to generate up to 10 GW of energy from a series of lagoons which exploit the tidal range of UK waters.[255] DECC officials met with the company in March 2013 to discuss the project.[256]

SOCIO-ECONOMIC AND ENVIRONMENTAL IMPACTS OF ALTERNATIVES

112. The socio-economic benefits of alternative proposals will need to be robustly assessed in the same way as the Hafren Power scheme. The Committee has been presented with little data about the impacts of alternative schemes. However, some advantages have been suggested in relation to the deployment of tidal lagoons:

Land-connected lagoons are located away from navigation channels, and therefore are unlikely to impact on the operations of Severnside ports.[257]
A lagoon design would be unlikely to impede the development of other marine technologies in the region.[258] The Regen SW and South West Marine Energy Park discussion paper suggested that a fixed barrage would "impact on downstream flow and hence tidal stream generation potential",[259] although Hafren Power maintain that the barrage is compatible with other technologies.[260]
Environmental impact is thought to be less since lagoons would not affect tides and water flow to the same extent and would not obstruct downstream and upstream migration of fish.
A smaller-scale lagoon design may be more likely to gain support from a broad range of stakeholders, while still offering potential for employment benefit and energy generation. Parsons Brinckerhoff claim their "stepping stones" lagoon offers "the potential for 4,000 direct jobs, of which 50% or more could be local". The Severn Tidal Power Group suggest that "the merits of developing such a scheme should be carefully considered".[261]

113. However, as CH2M HILL observed, some of the projects put forward remain in the early conceptual stages of development, and "do not present a sound business case". The firm argued that "A traditional barrage with tried and tested bulb turbine technology could be implemented relatively quickly and would provide the high degree of confidence that will be necessary to attract investors."[262] Hafren Power also suggested that tidal lagoons are "untried and unproven and would have similar impacts on ecology and wildlife to a barrage, which would need to be addressed".[263] The costs of marine technologies are currently high: at the time of writing wave and tidal stream technologies received five Renewable Obligation Certificates per MWh, equivalent to an approximate strike price of £200/MWh. Tidal lagoon and tidal barrage developers currently receive 2 ROCs/MWh, though this is set to reduce over the next four years.[264] The Energy Technologies Institute recommended that "a detailed consideration of the net contribution of each scheme, their capital and lifetime costs" is undertaken to assess relative economic benefits.

114. We conclude that a more incremental approach using alternative technologies (such as tidal lagoons) may have the potential to provide a lower-risk, lower-impact option than the Hafren Power barrage scheme. Whether these alternatives offer better value for money is far from clear at this stage. Any alternative proposals to the Hafren Power scheme would need to demonstrate the same robust evidence about the costs, environmental and socio-economic impacts which we require for the Hafren Power scheme. We recommend consideration is given to first developing a smaller scale tidal project, in order to build a stronger evidence base for assessing impacts, risks and costs before proceeding with any larger scale scheme. The Government should take this into consideration before approving the development of projects in the Severn estuary.

Future of tidal industry and Severn resource management

115. This inquiry has demonstrated the scale of public interest in the considerable potential of Severn marine resources, but the debate has to some extent suffered because it has been focussed so much on the merits or otherwise of the Hafren Power barrage scheme. Recent discussions at the Sustainable Severn Conference organised by Regen SW, RSPB and The Bristol Port Company suggested that stronger public governance of the marine resources in the Severn was needed.[265] This could be achieved through:

a clear policy and planning framework for the development of projects with a proactive approach from Government and public bodies;
a fair and open forum for stakeholder debate with an appointed representative body for Welsh and English interests, and
a "spatial plan" of Severn resources for energy developers which takes into account technology compatibility, socio-economic and environmental concerns.[266]

116. We conclude that the Government should continue to examine the energy generating potential of the Severn region in the event of Hafren Power's proposed barrage scheme not going ahead. We therefore recommend that the Government consider how a more proactive approach to Severn resource management could stimulate growth in the marine renewables industry and drive forward tidal projects in the region.

225 Ev 153a ; Atkins/Rolls Royce, Severn Embryonic Technologies Scheme, Concept Design for a Very-Low-Head Dual Generation Tidal Scheme for the Severn Estuary, February 2010 Back

226 See Error! Bookmark not defined. for further details of the MJ2 design Back

227 Ev 84a Back

228 Ev 107a Back

229 Q 273 Back

230 Q 108 Back

231 Ev 153a Back

232 As above Back

233 See Ev w5 and Ev w78 Back

234 Ev 91a Back

235 Ev w32 Back

236 Q 259 Back