A two-stage sodium converter coupled to a two-stage TEG: Parametric optimization

The aim of this study is to deeply study and analysis of energetic performance of the novel coupled system composed of a two-stage sodium thermal electrochemical converter and a two-stage thermoelectric generator. The main methods are to establish the model of the coupling system by considering the main irreversibilities, and obtain the analytical expressions of the power outputs and efficiencies of two subsystems and coupling system. The main novelties are to obtain the optimum ranges of critical parameters of the coupled system and give the reasonably matching conditions between the subsystems. The main contents of this study include that the influences of the intermediate and condenser temperatures of the sodium thermal electrochemical converter and current density of the first stage sodium thermal electrochemical converter as well as the electric current of the two-stage thermoelectric generator on the efficiency and power output density are discussed and the maximum power output density and efficiency of the system are calculated and compared with those of the single two-stage sodium thermal electrochemical converter and the existing coupling models. Results show that the maximum efficiency and maximum power output density of the coupled system attain 0.413 and 68.7 x 10(3) W m(-2) and exhibit an improvement of about 14.1% and 66.7% than those of the standalone two-stage sodium thermal electrochemical converter respectively, and the maximum efficiency of the whole system increase 37.7% compared with that of the existing coupling system. The results obtained indicate that the performance of the proposed system is greatly improved by efficient the exhaust heat utilization. In addition, the multi-objective and multi-parametric optimization analyses are adopted to search for the global optimization profile and validate the obtained findings.