What is exergy and how is it used in process analysis?

Exergy is the maximum useful work obtainable when a system equilibrates with its environment (dead state). Exergy = enthalpy - T0*entropy (relative to dead state). Unlike energy, exergy is destroyed in irreversible processes. Exergy analysis identifies: thermodynamic inefficiencies (where exergy destruction occurs), improvement opportunities (reduce irreversibility), and relative performance of process alternatives. Applications: power plant efficiency analysis, heat integration assessment, and second-law efficiency evaluation. Exergy destruction is proportional to entropy generation times dead state temperature.