Abstract Scope |
The Carnot principle of 1824 can be used as a guide to treat energy conversion, including thermoelectrics, in a more economical and unifying concept compared to traditional approaches. It identifies entropy as the central operational quantity in any kind of heat engine. In its generalized form, the principle states that the fall of entropy down its thermodynamic potential, which is the absolute temperature, releases energy that can be transferred to a useful process. An extensive thermodynamic quantity in the energy-receiving process is then raised in its corresponding thermodynamic potential. On the example of thermoelectric materials, transport equations for entropy, charge and energy are easily established, which identify the thermoelectric material by a material tensor instead of a kinetic matrix as in the traditional approach of the so-called thermodynamics of irreversible processes. Instead of so-called generalized forces, gradients of the more familiar thermodynamic potentials appear, i.e. temperature and electrical potential. |