A two-stage sodium thermal electrochemical converter: Parametric optimization and performance enhancement

Abstract

[EN]An asymmetric two-stage sodium thermal electrochemical converter and its optimum performance are studied by means of an improved analytical model including the main losses in the overall system. Based on the study of a single-stage sodium thermal electrochemical converter, the inner process is divided into two stages including one at the 1300 K temperature (evaporator) and the other at the 800–1300 K intermediate temperature with the aim of improving efficiency. The parametric optimum selection criteria of a few main parameters of the two-stage device are provided and the coupling of the separate stages in an overall optimum system in terms of the appropriate intermediate temperature is particularly stressed. The maximum efficiency of the proposed overall system can attain 36.2%, which is 17.5% higher than that of the best performing single-stage device, and increase up to 34.1% and 24.8% over the existing two-stage devices designed by two research groups, respectively. The Pareto front obtained from numerical multiobjective and multiparametric methods endorses previous findings and visually presents the space of the states and the energetic properties of the overall arrangement compared with the corresponding data for the isolated first and second stages.