Exergy - a definition

According to the laws of thermodynamics we know that energy is always conserved, that 'heat' is 'energy' is 'work', and that no system can convert a potential energy in 100% useful work.

Energy is this total potential available. It is a theoretical maximum amount of work which can never be fully achieved due to the inefficiencies in all systems (both natural and man-made). However, while 100% conversion from energy to work is not possible, the efficiency of the system can be controlled. More efficient systems convert more energy to work and are more desirable. Exergy loss minimisation is one approach that can be implemented to manage and improve a system's efficiency.

Exergy quantifies the potential energy within a system which can deliver useful work. The greater the exergy, the greater the potential work that can be extracted and used. Exergy efficiency expresses the extent to which that useful work is eventually extracted from the source.

This is only a brief introduction to the terminology. For further reading please download the thesis in the Downloads section of this web-site. Section 2.2 of the thesis will give you a more in-depth explanation.