(though he also introduced the concept of internal energy). The preferred direction
of spontaneous changes was represented by the Clausius statement and Kelvin–
Planck statement in terms of heat, heat transfer, and work. With the energy principle, thermodynamics began shifting from heat–work equivalence to the new
focus, energy and the transformation of energy (see Fig. 4.7). The process of this
change in focus from heat to energy was a long one with detours along the way, the
eventual completion of which was the formulation of the theory of exergy. A discussion of that development will be made in Chap. 7.
In a historical study of MEH and the general principle of energy conservation
(GPEC), Kipnis made the case, “the ‘principle of energy conservation’ process did
not start with a formulation of a general principle of energy conservation which
stimulated the development of particular concepts, such as mechanical equivalent of
heat. It will be shown that the opposite happened: it was the development of
mechanical equivalent of heat which led to the general principle of energy conservation” [9]. (In Sects. 3.2 and 3.3, the treatment departed from historical
development for a pedagogical reason.) In this development from heat to energy
and from particular to general, Kelvin and his energy principle played a pivotal role
[11].
It is striking in the manner Kelvin presented his principle. Von Baeyer commented on it with these words “The vague, metaphysical character of the principle
of dissipation of energy—the natural ‘tendency’ of energy toward dilution—contrasts curiously with the robust, tangible way in which Thomson described the
world [in his other scientific writings]” [12]. Uffink characterized the general
conclusions simply as “the un-argued statements of Kelvin” [13]. That is, Kelvin
treated the energy principle to be a self-evident proposition.
Nonetheless, von Baeyer had this assessment, “Inasmuch as the second law is
one of the pillars of physics, this was Thomson’s most significant contribution to
the science of thermodynamics, and overshadowed his invention of the absolute
scale of temperature, his early recognition of the importance of James Joule’s
work…” How can an “un-argued statement” have impacts even surpassing the
beautifully argued absolute scale of temperature?”
This assessment is correct. The reason for this assessment is that Kelvin
extended the characterization of energy from merely in terms of its conservation to
its conservation and its availability: the former was captured by the principle of
conservation of energy and the latter by the energy principle; together, they became
Statement #5, Table 3.1. One finds this characterization in the following passage as
given in the draft of his 1851 paper [4:174–200]
The difficulty which weighed principally with me in not accepting the theory so ably
supported by Mr. Joule was that the mechanical effect stated in Carnot’s Theory to be
absolutely lost by conduction, is not accounted for in the dynamical theory otherwise than
by asserting that it is not lost [i.e., the assertion of energy conservation]; and it is not known
that it is available to mankind. The fact is, it may I believe be demonstrated that the work is
lost to man irrecoverably; but [even though energy is] not lost in the material world.
Although no destruction of energy can take place in the material world without an act of
4.7 The Energy Principle, A Self-evident Proposition?
85
of spontaneous changes was represented by the Clausius statement and Kelvin–
Planck statement in terms of heat, heat transfer, and work. With the energy principle, thermodynamics began shifting from heat–work equivalence to the new
focus, energy and the transformation of energy (see Fig. 4.7). The process of this
change in focus from heat to energy was a long one with detours along the way, the
eventual completion of which was the formulation of the theory of exergy. A discussion of that development will be made in Chap. 7.
In a historical study of MEH and the general principle of energy conservation
(GPEC), Kipnis made the case, “the ‘principle of energy conservation’ process did
not start with a formulation of a general principle of energy conservation which
stimulated the development of particular concepts, such as mechanical equivalent of
heat. It will be shown that the opposite happened: it was the development of
mechanical equivalent of heat which led to the general principle of energy conservation” [9]. (In Sects. 3.2 and 3.3, the treatment departed from historical
development for a pedagogical reason.) In this development from heat to energy
and from particular to general, Kelvin and his energy principle played a pivotal role
[11].
It is striking in the manner Kelvin presented his principle. Von Baeyer commented on it with these words “The vague, metaphysical character of the principle
of dissipation of energy—the natural ‘tendency’ of energy toward dilution—contrasts curiously with the robust, tangible way in which Thomson described the
world [in his other scientific writings]” [12]. Uffink characterized the general
conclusions simply as “the un-argued statements of Kelvin” [13]. That is, Kelvin
treated the energy principle to be a self-evident proposition.
Nonetheless, von Baeyer had this assessment, “Inasmuch as the second law is
one of the pillars of physics, this was Thomson’s most significant contribution to
the science of thermodynamics, and overshadowed his invention of the absolute
scale of temperature, his early recognition of the importance of James Joule’s
work…” How can an “un-argued statement” have impacts even surpassing the
beautifully argued absolute scale of temperature?”
This assessment is correct. The reason for this assessment is that Kelvin
extended the characterization of energy from merely in terms of its conservation to
its conservation and its availability: the former was captured by the principle of
conservation of energy and the latter by the energy principle; together, they became
Statement #5, Table 3.1. One finds this characterization in the following passage as
given in the draft of his 1851 paper [4:174–200]
The difficulty which weighed principally with me in not accepting the theory so ably
supported by Mr. Joule was that the mechanical effect stated in Carnot’s Theory to be
absolutely lost by conduction, is not accounted for in the dynamical theory otherwise than
by asserting that it is not lost [i.e., the assertion of energy conservation]; and it is not known
that it is available to mankind. The fact is, it may I believe be demonstrated that the work is
lost to man irrecoverably; but [even though energy is] not lost in the material world.
Although no destruction of energy can take place in the material world without an act of
4.7 The Energy Principle, A Self-evident Proposition?
85