An Environmental Life Cycle Assessment of Energy Systems Leading to a Pathway for a Low Carbon Economy

  • Katharine Kelly

Student thesis: Doctoral ThesisPhD


In 2008, the UK Government enforced the target to reduce the UK carbon account for the year 2050 to at least 80% less than the 1990 baseline. In order to meet this ambitious target it is widely thought that the UK energy future should be ‘electrified’ as a suite of low carbon generation technologies provide ever increasing proportions of electricity supply. This work has identified and investigated two technologies that could make significant contributions to low carbon power supply in the UK; that of industrial combined heat and power, CHP, and tidal power. Life cycle case studies were completed on an existing UK CHP plant and the Severn Barrage scheme as it was proposed until 2010. The Severn Barrage assessment has shown that the lifetime environmental impact is dominated by the operation stage. This is contrary to previously published studies, which have underestimated (Parsons Brinckerhoff Ltd; Black and Veatch Ltd; 2010)(Roberts 1982)(Spevack, Jones and Hammond 2011) or even ignored (Black & Veatch 2007)(Woollcombe-Adams, Watson and Shaw 2009)the contribution from this life stage. Furthermore, the results have demonstrated that the impact intensity of power from the Barrage is almost entirely reliant on that of the National Grid mix which provides the operational power required. It has been shown a large improvement to the impact of the operation stage can be made by removing the electricity demand for ‘flood pumping’. However, even without ‘flood pumping’, the impact of the power demand for plant operation will dominate. Hence the greatest improvements to the schemes lifetime impact can be made via the National Grid mix itself. The industrial CHP assessment has shown that there are large impact savings available from widespread implementation against the current and the baseline National Grid mixes. However, even if it is assumed that units are exclusively bio-gas fuelled, the carbon intensity of the power generated is very likely to exceed that of the low carbon Grid mix by 2050. The discussion shows that the interactive roles that these two technologies could play, with each other and the evolving Grid mix, on the pathway to 2050 is, however, more complex than simply considering the isolated impact intensity. The commissioning of the Severn Barrage could mark the point at which the carbon intensity of the National Grid falls below that of CHP. However because the carbon intensity of the plant is reliant on the national power supply, it is argued that further CHP implementation should only be stopped if there is a suitable low carbon and low impact alternative that can fill the capacity gap. This thesis concludes that to fear that today’s CHP schemes could represent a technology ‘lock-in’ in the long term future is to underestimate the role the technology has in the current and more short term future Grid mix.The work presented demonstrates the importance of life cycle thinking in the development of a low impact energy strategy. The discussion has also shown the importance of scenarios in assessing the requirements for such an ambitious change. The pursuit of change implies that the future is necessarily dynamic. The work has illustrated that scenario thinking allows exploration of potential strategy decisions and hence, is essential to having confidence in the decisions made.
Date of Award15 Dec 2013
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorMarcelle McManus (Supervisor)


  • life cycle assessment
  • low carbon
  • energy

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