End-of-life management of solid oxide fuel cells

This thesis reports on research undertaken to investigate the end-of-life management of solid oxide fuel cells (SOFC), through the definition of a framework and the development of a multicriteria evaluation methodology which together support comparison of alternative end-of-life scenarios. The primary objective of this research is to develop an understanding of the challenges and opportunities arising during the end-of-life phase of the technology, such that any conflicts with end-of-life requirements might be addressed and opportunities for optimising the end-of-life phase fully exploited. The research contributions can be considered in four principal parts. The first part comprises a review of SOFC technology and its place in future sustainable energy scenarios, alongside a review of a growing body of legislation which embodies concepts such as Extended Producer Responsibility and Integrated Product Policy. When considered in the context of the life cycle assessment literature, which clearly points to a lack of knowledge regarding the end-of-life phase of the SOFC life cycle, this review concludes that the requirement for effective end-of life management of SOFC products is an essential consideration prior to the widespread adoption of commercial products. The second part of the research defines a framework for end-of-life management of SOFCs, which supports clarification of the challenges presented by the SOFC stack waste stream, as well as identifying a systematic approach for addressing these challenges through the development of alternative end-of-life management scenarios. The framework identifies a need to evaluate the effectiveness of these end-of-life scenarios according to three performance criteria: legislative compliance; environmental impact; and economic impact. The third part of the research is concerned with the development of a multi-criteria evaluation methodology, which combines conventional evaluation methods such as life cycle assessment and cost-benefit analysis, with a novel risk assessment tool for evaluating compliance with current and future legislation. A decision support tool builds on existing multi-criteria decision making methods to provide a comparative performance indicator for identification of an end of-life scenario demonstrating low risk of non-compliance with future legislation; low environmental impact; and a low cost-benefit ratio. Finally, the validity of the framework for end-of-life management is tested through the completion of two case studies. These case studies demonstrate the flexibility of the framework in supporting a reactive end-of-life management approach, whereby end-of-life management is constrained by characteristics of the product design, and a proactive approach, whereby the impact of design modification on the end-of-life phase is explored. In summary, the research clearly highlights the significance of the end-of-life stage of the SOFC life cycle. On the one hand, failure to manage end-of-life products effectively risks undermining the environmental credentials of the technology and is likely to lead to the loss of a high-value, resource-rich material stream. On the other hand, the early consideration of aspects identified in the research, especially while opportunities remain to influence final product design, represents a real opportunity for optimising the end-of-life management of SOFC products in such a way as to fully realise their potential as a clean and efficient power generation solution for the future.