7. Exergy performance measurement

We give below some exergy efficiencies and dissipative factors for the most common systems. Exergetic efficiency, η _ex , based on the second principle of thermodynamics, like energy efficiency, η _en , which in turn is based on the first principle of thermodynamics, measures the share of a product in relation to a resource for a given process or system. Other definitions of exer-gic efficiency can be found, such as the ratio of outgoing to incoming flow, etc. ${\eta }_{\text{en}}=\frac{\text{ produit (énergétique) }}{\text{ ressource (énergétique) }}\text{ et }{\eta }_{\text{ex}}=\frac{\text{ produit (exergétique) }}{\text{ ressource (exergétique) }}$