Exergy(Ex) is defined as the amount of work (=entropy - free energy) a system can perform when it is brought into thermodynamic equilibrium with its environment.
i.e. IAmax I = Exergy(Ex); ( Jorgensen et al., 1999
From: Towards A Thermodynamic Theory For Ecological Systems, 2004
girl: "Baby does my butt look big in this?"
boy: turns and stares at his girlfriendsginormous butt - "hmmm, um....maybe, possibly you could think about doing some exercycling. Maybe."