Conclusion

Analysis of the operating principle of energy converters has shown that a minimum of four energy sources is required, two for each type of energy used in the conversion. However, experience shows that some thermal generators use only one heat source. This is due to the fact that the extensive variable of this energy, entropy, is "creatable" and indestructible. This is a consequence of the second principle of thermodynamics, which is also the principle of the natural transfer of energy from a source with a high intensive variable to a source with a lower value of the same variable.

Although unreal, a Carnot motor or generator is useful for qualifying the behavior of a real machine, since it corresponds to an ideally functioning machine. In fact, to give information on the quality of a motor or generator machine, we use the ratio between its thermodynamic efficiency...