What is it about?

The now common application of thermodynamic ideas outside the sphere of engineering is not without its critics. The concept of 'exergy', which follows from the Second Law of Thermodynamics, is viewed as providing the basis of a tool for resource and/or emissions accounting. It is also seen as indicating natural limits on the attainment of sustainability. The link between the efficiency of resource utilisation, pollutant emissions, and 'exergy consumption' is real, but not direct. Methods of energy and exergy analysis are therefore employed to critically evaluate thermodynamic concepts as measures of sustainability.

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Why is it important?

Thermodynamic concepts have been utilised by practitioners in a variety of disciplines with interests in environmental sustainability, including ecology, economics and engineering. Widespread concern about resource depletion and environmental degradation are common to them all. It has been argued that these consequences of human development are reflected in thermodynamic ideas and methods of analysis; they are said to mirror energy transformations within society.

Perspectives

The exergy method was used by Hammond & Stapleton (Proc. Instn Mech. Engrs Part A: Journal of Power and Energy, 2001, 215 (2): 141-162 [DOI: 10.1243/0957650011538424]) to determine the Second Law 'improvement potential' for some important elements of the United Kingdom energy system. Electricity generation, together with final energy demand in the domestic sector and in transport, were found to account for nearly 80% of exergetic improvement potential. This poor thermodynamic performance is principally due to exergy losses in combustion and heat transfer processes associated with power generation, space heating, and the main transport modes. Nevertheless, Allen, Hammond & McKenna (Proc. Instn Mech. Engrs Part A: Journal of Power and Energy, 2017, 231 (6): 508-525 [DOI: 10.1177/0957650917693483]) more recently argued that such concepts are typically employed only by way of an analogy with, or resemblance to, physical processes when used outside the realm of energy systems. But they suggested that there would be some scope to employ exergy analysis in order to identify opportunities for energy or heat cascading within and between manufactories.

Professor Emeritus Geoffrey P Hammond
University of Bath

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This page is a summary of: Engineering sustainability: thermodynamics, energy systems, and the environment, International Journal of Energy Research, May 2004, Wiley, DOI: 10.1002/er.988.
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