Performance of a Thermoelectric Module Using the Thermodynamic Relationship Temperature-Entropy (T-S)

In this paper, the performance of a thermoelectric module is analysed using the thermodynamic diagram TemperatureEntropy. This diagram can be used as a graphical tool which allows for the analysis of thermoelectric processes, both reversible and non-reversible, in an elemental pair or thermoelectric elements. A similarity is found between the Seebeck coefficient and entropy per unit of electrical charge. This allows for the use of the Seebeck coefficient and absolute temperature as coordinates in a representative Cartesian system. All processes, both reversible and non-reversible, in a pair of thermoelectric elements can be represented in the above mentioned system. This analysis is completed with the identification of several graphic elements such as lines and areas, and their association to different equations and thermodynamic relationships of the thermoelectric module performance. This approach is very useful in the analysis of thermoelectric modules as it is performed from an engineering point of view in classical thermodynamics. Seebeck coefficient and entropy The Seebeck coefficient (σ) can be expressed according to equation 1. This is an expression from the Onsager relations [1] and [2] considering a bar of a thermal and electrical conductor material under the application of a potential electrical difference (ε) and a difference of temperature (∆T).