A review on thermoelectric cooling parameters and performance

This paper deals with a review of the main research aspects concerning the formulation of the parameters indicating the characteristics and performance of thermoelectric cooling devices, with particular reference to a number of recent publications. The specific aspects addressed include some practical considerations referring to the thermoelectric figure of merit, the characterization of the cooling capacity, and the assessment of the coefficient of performance (COP). The contribution of this paper starts by categorizing the topics addressed by recent review papers, showing that these reviews generally had a wide focus and provided little specific details on thermoelectric cooling parameters and performance. Then, the dimensionless thermoelectric figure of merit is addressed by focusing on its conventional and modified definitions and indicating the values obtained for different thermoelectric cooling materials. Furthermore, the expressions of the cooling capacity for single-stage and multi-stage thermoelectric coolers are reviewed. Concerning the COP, its dedicated expressions are constructed starting from the classical formulation and introducing additional factors or modifications in order to take into account the Thomson effect, the dependence on temperature of the thermoelectric materials, and the effects of the electrical contact resistance, thermal resistance, thermoelement length and current. Finally, on the basis of the indications taken from the literature, further considerations are included on the COP values found in thermoelectric cooling applications, as well as on how to obtain COP improvements.