An Indicative Energy Technology Assessment of the ‘Shoots Barrage’ Tidal Power Scheme (UK)

What is it about?

Several tidal power schemes have been proposed for the River Severn Estuary between the South West of England and Wales. Here the so-called Shoots Barrage scheme has been evaluated using various appraisal techniques to determine its net energy output, carbon footprint, and financial investment issues. It would located near the Severn road crossings in the United Kingdom (UK), involve an estimated to cost £3.2 bn to construct, and could generate around 2.7 TWh/yr [or just about 0.7% of UK electricity supply]. An energy analysis was conducted comprising a detailed investigation into the cradle-to-site, operation and maintenance energy consumption for the two schemes. The total energy output of the scheme over its foreseen lifespan of 120 years was calculated in order to determine the associated energy gain ratios (EGR) and energy payback periods (EPP). The former was found to vary from 19.2:1 to 23.8:1, whilst the latter was estimated to be about 9.16 years. On an ‘opportunity cost’ basis the EGR rose to be between 22.3:1 and 57.9:1 with an EPP of about 6.6 years. Overall, the present analysis suggests that the Shoots scheme has relatively attractive ‘figure of merit’ in energy terms. This system boundary was then applied for carbon accounting, and this yielded a ‘footprint’ of about 8.0 gCO2/kWhe. Finally, the economics of the Shoots Barrage scheme was evaluated in some detail. This suggested that the most likely Levelised Unit Electricity Cost (LUEC) value was 10.8p/kWhe (using the HM Treasury declining TDR), which is a higher figure than that obtained by UK Government, i.e., using a discount rate of 8%.

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Why is it important?

The River Severn Estuary lies between the South West of England and Wales in the United Kingdom (UK). It experiences the second largest tidal range (~14 m) in the world and, over the years, a large number of private and UK Government studies have looked for ways to harness the tidal power for electricity generation. But the concept of a Severn Barrage has remained at the feasibility stage since the 1920s, due mainly to concerns about economic viability and environmental impact [8, 9]. Nevertheless, with growing concern over anthropogenic climate change and a desire to ensure a secure energy supply as fossil fuels diminish, the UK Government have committed itself to both the carbon reduction target incorporated in its 2008 Climate Change Act, and to producing at least 15% of its energy from renewable sources by 2020. A large-scale Severn Barrage tidal power scheme that was operational by 2020 would provide an estimated supply of 4.4% of the total energy demand of the UK. This would be the so-called Cardiff-Weston barrage that would be constructed between Lavernock Point near the town of Barry (on the south Wales coast) and Brean Down in Somerset (adjacent to Weston-super-Mare). Thus, by exploiting the tidal range in the Severn Estuary, the UK could improve the energy diversity of its supply mix via such a renewable and sustainable source. A tidal power project in the Severn Estuary could therefore make a significant contribution to reducing GHG emissions from the power sector, as well as helping to meet both international and domestic climate change targets.

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