Date of Award
Doctor of Philosophy (PhD)
Terry M Tritt
The need for efficient energy conversion and utilization has magnified on account of global environmental concerns, leading to a dramatic rise in focus on technologies that can accomplish such enhanced efficiencies. In this context, thermoelectrics (TEs) have emerged as a prominent platform on account of rigorous research that has enabled a significant leap in their conversion efficiencies, which enhances their potential to lower fossil fuel consumption. However, the advent of novel TEs has been accompanied by growing concerns about the use of scarce and toxic constituent elements in most of these materials/systems, raising questions about their eco-friendliness. While these concerns must be suitably addressed, the very nature of looking at TEs solely in terms of either benefits during their usage, or at issues with their constituents, confines the notion of sustainability to one or few stages of their life cycle. This creates doubts about the traditional claims of TEs being ecofriendly, since other environmental issues associated with their life cycle, such as impacts caused by their production or end-of-life treatment, remain neglected. These gaps hinder a true assessment of ecological credentials of TEs as an energy harvesting platform, and also make it difficult to provide adequate directions to policymakers and other stakeholders on the nature of steps required to make this platform ecologically suitable and economically viable.
To ameliorate these gaps, this work explores the environmental profile of TEs using life cycle assessment (LCA). TE devices – modules and generators – were evaluated for environmental performance across their life cycle for three applications differing in their nature of waste heat emission and mobility. These were: (a) baseload coal-based power plant (static, constant emission); (b) peak load natural gas-based power plants (static, periodic emission); and (c) automobiles (mobile, intermittent emission). For all end-uses, TEs were assessed on various impacts. The first-ever exhaustive inventory analysis to date was conducted for production of TE devices, while three end-of-life (EOL) scenarios were considered to determine the benefits and pitfalls of recycling TEs as these use scarce constituents. Subsequently, the results from these LCA analyses were used to distill key findings and postulate principles for developing sustainable thermoelectrics.
LCA analysis of TEs showed that both high electricity consumption for TE processing and use of constituent elements that emit toxic waste during their extraction and refining, caused the bulk of their production-related impacts. Further, while TE devices were observed to be environmentally sound for applications involving continuous waste heat emission (coal-based power), they showed ineffectiveness for periodic (gas-based electricity) and intermittent waste heat emission (automobiles) to varying degrees. In addition, recycling of TEs was seen to have moderate influence on their ecological output, with heat exchanger-based components playing a more significant role. Lastly, using the results from LCA analyses, eight sustainability principles were postulated for TEs encompassing their entire life cycle, that can guide policymakers to work with other stakeholders on enhancing overall eco-friendliness of this platform.
Iyer, Rakesh Krishnamoorthy, "Thermoelectrics: Ecological Profile and Fundamental Principles for Sustainability" (2020). All Dissertations. 2656.