Exergy - Wikipedia, the free encyclopedia: "Exergy is the maximum amount of work that can be extracted from a physical system by exchanging matter and energy with large reservoirs in a reference state. This work potential is due to either a potential due to random thermal motion, kinetic energy, potential energy associated with a restoring force, or the concentration of species relative to a reference state. While energy is conserved, exergy can be destroyed. While there is a constant amount of energy in the universe, the amount of exergy is constantly decreasing with every physical process."