A technology assessment of the proposed Cardiff–Weston tidal barrage, UK

Geoffrey P Hammond,Craig I Jones,Rachel Spevack

doi:10.1680/jensu.16.00015

Abstract

Several tidal power schemes have been proposed for the Severn estuary between south-west England and Wales, UK. In this paper the so-called Cardiff–Weston barrage is evaluated using various sustainability appraisal techniques to determine its net energy output, carbon dioxide footprint and financial investment criteria, alongside various critical technical and environmental issues. The barrage would be located seaward of the Severn Road crossings, involve an estimated cost of £21 billion to construct and could potentially generate some 16·8 TWh/year – about 4·4% of the UK electricity demand. An indicative energy technology assessment is undertaken to evaluate this tidal power scheme over its foreseen lifespan of 120 years in terms of its ‘cradle-to-site’, operation and maintenance requirements. The present analysis suggests that the proposed Cardiff–Weston barrage would yield relatively attractive ‘figures of merit’ in terms of its net energy and carbon dioxide emissions, although its financial performance is poorer than that of alternative power generators. Comparisons are also made with the much smaller Shoots barrage scheme proposed upstream of the Severn Road crossings, which is favoured by environmental groups due to its more benign ecological and environmental impacts.

Highlights

1.1 Background Electricity generation presently contributes approximately 30% of UK carbon dioxide (CO2) emissions (Alderson et al, 2012; Post, 2007), the principal greenhouse gas (GHG), having an atmospheric residence time of about 100 years (Hammond, 2000)
6.1 Energy analysis 6.1.1 Cradle-to-site analysis Embodied energy associated with the material requirements for the Cardiff–Weston tidal barrage were obtained from the ICE database (Hammond and Jones, 2008, 2011b)
The largest contributors in terms of the energy requirements for the scheme were associated with cement (28%) and the hydroturbines (22%). This contrasts with the Shoots barrage (Hammond et al, 2014), for which 58% of the embodied energy was related to limestone rock, assumed to be quarried and shipped from the Glensanda superquarry in Scotland

Summary

Introduction

1.1 Background Electricity generation presently contributes approximately 30% of UK carbon dioxide (CO2) emissions (Alderson et al, 2012; Post, 2007), the principal greenhouse gas (GHG), having an atmospheric residence time of about 100 years (Hammond, 2000). The River Severn estuary lies between south-west England and Wales in the UK It experiences the second largest tidal range (~14 m) in the world (Binnie, 2016) 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 (Elliott, 2012; RCEP, 2000). This has recently been motivated by the growing concern over anthropogenic climate change and a desire to ensure a secure energy supply as fossil fuel use diminishes. Financial appraisal uses the market rate of interest (net of inflation) as a lower bound and indicates the real return that would be earned on a private sector investment

Methods

Results

Conclusion