Simulation of a thermo-electrochemical cell with graphite rod electrodes

Abstract

The rapid development of human society has resulted in the extensive release of waste heat. The thermo-electrochemical cell (TEC), a cutting-edge technology that converts low-grade waste heat into electricity, has garnered increasing attention. However, the complex interactions among various processes, such as fluid flow, electrochemical reactions and heat transfer, make it challenging to evaluate their effect on the overall performance of the TEC. Understanding the synergistic mechanisms and coupling effects of these processes is crucial for optimizing and implementing TECs in practical applications. In this paper, a mathematical model is developed by coupling electrochemical reactions and heat/mass transfer. The distributions of ion concentration, electrolyte velocity and temperature are analyzed under varying temperature differences and electrode distances. The results demonstrate a significant interaction between heat transfer and electrolyte flow. Higher temperatures not only improve the open circuit voltage, but also promote ion transport convection and hence enhance the current density. In addition, a higher concentration of ions or smaller electrode spacing exhibits an apparently improved performance of the TEC, due to the facilitated ion transport and reduced concentration overpotential. Notably, electrode spacing has a negligible effect on the maximum power density of the TEC under a constant heat flux, but it does enhance the current density due to the combined effect of heat and ion transfer. Overall, the proposed mathematical model provides deeper insight into the physical–chemical processes involved in TECs and offers valuable guidance for TEC design and practical applications.