Exergy Analysis—A Different Perspective on Energy Part 1: The Concept of Exergy

Abstract

Exergy analysis is a technique at the forefront of applied thermodynamics research whereby systems that utilize energy are assessed in the light of the second law of thermodynamics. All forms of energy transfer and transport can be represented by equivalent exergy transfers which are, in fact, the quantities of work that could be produced from the same types of energy transfer or transport by perfect thermodynamic devices free to interact with a specified reference environment. Energy is conserved and this is a fundamental physical law. Whereas conventional energy analyses can only account for where energy is distributed, or lost from systems of interest, exergy analysis can highlight where it is used inefficiently. This paper describes and develops the exergy analysis concept. The exergy transfers associated with various types of energy transfer and transport are defined and an ‘exergy analysis toolbox’ is described. In Part 2 of the paper a universal rational efficiency is described and a number of worked examples are presented to illustrate the application of exergy analysis. Some of the present limitations of the technique and areas for future development are described.