ABSTRACT
This is an entry on efficiency assessment of energy systems covering fundamental thermodynamic concepts. A solid thermodynamic background for the accurate understanding of the first law and the second law of thermodynamics as well as entropy and exergy concepts is needed for developing energy‐ and exergy‐based efficiencies for various energy conversion systems. This part is concluded with general definitions of efficiencies based on energy and exergy concepts. These definitions are applied to various energy conversion systems in the entry on “Efficiency Assessment of Energy Systems: Applications” in this encyclopedia.
