A brief perspective on the physics of performance estimation of thermoelectric generators

Estimating thermoelectric (TE) performance is vital for guiding thermoelectric research. A thermoelectric generator (TEG) is made of p-type and n-type semiconductor materials and the material properties are typically temperature dependent. Estimating the performance of a TEG involves solving the thermoelectric heat balance equation, and since the TE material properties are temperature dependent, this equation is a second order non-linear partial differential equation. Such equations can only be solved numerically using methods such as finite element methods. As these numerical methods are time consuming and costly, some approximate analytical methods exist, the constant properties model (CPM) being the backbone of all of them. Different papers suggest different modifications and comments on the CPM and it is not clear which assumptions and modifications work for all scenarios. In addition, the physics behind these models is not always completely analyzed. This work presents a critical view on the physics of thermoelectric generation and provides perspective on the commonly claimed errors and misconceptions with CPM, reviewing the popular approaches and suggestions for modifications on the use of CPM. Initially a brief overview of the relevant concepts for theoretical performance estimation of TEGs is presented in order to understand the physics of TEG. Finally, recommendations for the use of these models is provided.