Engineering Sustainability: Thermodynamics, Energy Systems and the Environment

Summary Thermodynamic concepts have been utilized 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. 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 more traditional use of the exergy method is illustrated by a number of cases drawn from the United Kingdom energy sector: electricity generation, combined heat and power schemes, and energy productivity in industry. This indicates the scope for increasing energy efficiency, and the extent of exergetic ‘improvement potential’, in each of these areas. Poor thermodynamic performance is principally the result of exergy losses in combustion and heat transfer processes. However, the application of such thermodynamic ideas outside the sphere of engineering is not without its critics. The link between the efficiency of resource utilization, 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.