Exergy analysis and resource accounting

• Main Author: Gaudreau, Kyrke
• Language: en
• Published: 2009
• Subjects: Exergy; Resource accounting; Self-organization; Complex systems; Ecology; Emergy; Eco-exergy; Exergy Replacement Cost; Environmental and Resource Studies
• Online Access: http://hdl.handle.net/10012/4507

The objective of this thesis is to establish the utility and limitations of using exergy (a thermodynamic measure of energy quality, or ability to perform work) as a resource consumption metric, and to investigate what role exergy may play in resource consumption decision-making. To do so, this thesis assessed three exergy-based resource consumption methodologies: the Exergy Replacement Cost; Eco-exergy; and Emergy. Furthermore, fundamental properties of exergy were revisited, including the exergy reference state, and the derivations of both concentration and non-flow exergy. The results of the analysis indicate three significant problem areas with applying exergy toward resource valuation. First, the exergy derivation level conflicts with the resource valuation level regarding important requirements and assumptions: the exergy reference environment is modelled as an infinitely large system in internal chemical equilibrium, and this is in incomparable to the real world; and, the derivation of non-flow exergy values items based solely upon chemical concentrations, whereas at the resource consumption level, work producing items are valuable based primarily upon chemical reactivity. Second, exergy proponents have not adequately addressed the many different and critical perspectives of exergy, including exergy as: harmful or helpful; organizing or disorganizing; a restricted or unrestricted measure of potential useful work; and applied to value systems or specific items. Third, none of the resource consumption methodologies properly apply exergy: the Exergy Replacement Cost primarily focuses on mineral upgrading; Eco-exergy is improperly derived from exergy; and Emergy has switched from being energy-based to exergy-based without any reformulation of the methodology. For the reasons provided above, among others, this author concludes there is currently no justified theoretical connection between exergy and resource value, and that there is a disjunction between how exergy is derived and how it is applied. Non exergy-based applications for the three resource consumption methodologies are proposed.