Performance optimization and parametric selection strategies of a sodium thermal electrochemical converter-thermophotovoltaic cell integrated system

Abstract

Explorations of efficient thermoelectric devices to abandon fossil fuels are widely concerned. Sodium thermal-electrochemical converter can efficiently convert heat into electricity, but much heat dissipated from the converter restricts its performance. A novel integrated system composed of a sodium thermal-electrochemical converter and a thermophotovoltaic cell is first proposed to realize hierarchical utilization of energy. Expressions for the power output densities and efficiencies of each subsystem and integrated system are derived. Performance characteristics of the integrated system are theoretically analyzed. Influences of the current density of the converter, the voltage output and bandgap energy of the cell, and the electrode area ratio of the two subsystems on the integrated systemic performance are comprehensively evaluated. The maximum power output density and efficiency of the integrated system attain, respectively, 18.54 Wcm −2 and 48.93%, which increase, respectively, 350.0% and 35.16% compared with those of the two-stage sodium thermal-electrochemical converter, and 188.3% and 41.42% compared with those of the sodium thermal-electrochemical converter-thermoelectric generator integrated system. The optimum selection criteria of main parameters are given, providing valuable references for the actual manufacture and operation. The results show that the materials with bandgap energy around 0.290 eV are preferred for the fabrication of the proposed integrated devices. • A thermophotovoltaic cell is coupled to a sodium thermal electrochemical converter. • The waste heat from the converter is efficiently utilized by the cell. • The maximum efficiency 48.93% and power output density 18.54 Wcm −2 are obtained. • Optimal selection criteria of main parameters are given. • Advantages of the present system over other relevant coupled systems are expounded.