7
Free Energy, Exergy, and Energy: The
Exergetic Content of Energy
Abstract
Kelvin had introduced the general idea of available energy. The advent of the
entropy principle led to, in quick succession, the formulation of equilibrium
thermodynamics by Gibbs—which was the prized fruit of the Kelvin–Clausius
synthesis. One of its important results was the concept of free energies, which
provided the general idea of available energies with specific examples—
especially the Gibbs free energy of electrochemical energy!electrical work.
Further development of available energy has evolved into the theory of exergy.
Significantly, both the first law and the theory of exergy can be formulated for an
engineering device’s control volume. In that formulation, the exergy treatment is
reducible to the Carnot–Kelvin formula, a key tool in mechanical engineering, as
well as to the Gibbs free energy, a key tool in chemical engineering.
Keywords
Thermodynamic potentials Á Helmholtz free energy Á Gibbs free energy Á Exergy
Á Material exergy Á Energy equation for open systems Á Exergy equation for
open systems Á Definition of energy Á Spontaneous energy conversion Á
Mechanical theory of heat (MTH)
7.1 Thermodynamic Potentials and Free Energies
This chapter introduces the concepts of free energy and exergy. Beginning with
Chap. 4, we have been centrally concerned with the phenomena of the natural
tendency of the material world and how this tendency is intimately related to the
production of work. Both of the above concepts help to deepen our understanding
of this issue. It turns out that the only way to deliberate about energy meaningfully
is through thinking in terms of entropy and exergy. In this section, we begin with
free energies.
© Springer Nature Switzerland AG 2020
L.-S. Wang, A Treatise of Heat and Energy, Mechanical Engineering Series,
https://doi.org/10.1007/978-3-030-05746-6_7
157
Free Energy, Exergy, and Energy: The
Exergetic Content of Energy
Abstract
Kelvin had introduced the general idea of available energy. The advent of the
entropy principle led to, in quick succession, the formulation of equilibrium
thermodynamics by Gibbs—which was the prized fruit of the Kelvin–Clausius
synthesis. One of its important results was the concept of free energies, which
provided the general idea of available energies with specific examples—
especially the Gibbs free energy of electrochemical energy!electrical work.
Further development of available energy has evolved into the theory of exergy.
Significantly, both the first law and the theory of exergy can be formulated for an
engineering device’s control volume. In that formulation, the exergy treatment is
reducible to the Carnot–Kelvin formula, a key tool in mechanical engineering, as
well as to the Gibbs free energy, a key tool in chemical engineering.
Keywords
Thermodynamic potentials Á Helmholtz free energy Á Gibbs free energy Á Exergy
Á Material exergy Á Energy equation for open systems Á Exergy equation for
open systems Á Definition of energy Á Spontaneous energy conversion Á
Mechanical theory of heat (MTH)
7.1 Thermodynamic Potentials and Free Energies
This chapter introduces the concepts of free energy and exergy. Beginning with
Chap. 4, we have been centrally concerned with the phenomena of the natural
tendency of the material world and how this tendency is intimately related to the
production of work. Both of the above concepts help to deepen our understanding
of this issue. It turns out that the only way to deliberate about energy meaningfully
is through thinking in terms of entropy and exergy. In this section, we begin with
free energies.
© Springer Nature Switzerland AG 2020
L.-S. Wang, A Treatise of Heat and Energy, Mechanical Engineering Series,
https://doi.org/10.1007/978-3-030-05746-6_7
157