An empirical assessment of sector level exergy analysis

By relating to both the quality and quantity of energy flows, exergy analysis can be used to assess the improvement potential of thermodynamic systems. Exergy analysis has previously been applied at the economy level in order to provide a measure of the scope for efficiency improvement. While this approach can help to guide progress, meaningful analysis that takes full advantage of the insights of exergy, at this scale, retains some challenges. This study explores three relevant considerations to the interpretation and use of exergetic improvement potential applied at the macro (economy) scale. Specifically: (i) the nature of the relationship between improvement potential and the changes in efficiency that occur, (ii) the relative significance of exergy embodied in flows and (iii) the sensitivity of efficiency calculations to the definition of systems outputs. The nature of these considerations is evaluated empirically, using historic data. It is shown that exergy can provide useful information but that there is a complementary role for energy analysis. The scope for savings outside of direct “improvement potential” is also noted. It is hoped that appreciation of these considerations will lead to more effective exergy analysis at the economy scale, with its advantages and also limitations properly understood.