Exergy Concept and its Application

We conventionally use energy-based efficiency measures to assess energy systems. Energy-based measures of merit, however, do not really indicate how nearly performance efficiency approaches the ideal. In fact, energy measures can confuse and sometimes lead to wrong decisions and wasteful resource allocations. Exergy analysis, which is based on the second law of thermodynamics, avoids the difficulties associated with energy methods, and allows efficiencies to be clearly understood and measures to improve efficiency to be properly assessed. In this article, exergy and its application as an analysis tool are described, and an example illustrates the benefits of using exergy. In addition, the environmental implications of exergy and the ties between exergy and economics are described. The results indicate that exergy methods should prove useful to engineers and scientists, as well as decision and policy makers.