An alkali metal thermoelectric converter hybridized with a Brayton heat engine: Parametric design strategies and energetic optimization

Abstract

A model for a novel integrating system consisting of an alkali metal thermoelectric converter and a non-recuperative irreversible Brayton heat engine is presented. The efficiency and power output density of the overall system is analyzed at light of the main characteristic losses in each subsystem: the thickness of the electrolyte, the current density of the converter, and the internal losses of the Brayton cycle coming from the compressor and turbine. A detailed study on the behavior of the overall maximum power and maximum efficiency regimes is also presented. An analysis on compromise performance regimes from multi-objective and multi-parametric optimization techniques based on the Pareto front, for both the subsystems and the overall system, enhance the obtained results. The numerical results of the present model are compared with those of alkali metal thermoelectric converter working alone and with other different existing hybrid models. It is found that the exhaust heat discharged by the converter can be efficiently utilized by an irreversible Brayton heat engine. So, the maximum efficiency and maximum power output density of the present model attain 41.7% and 116×103 W/m2 which increase about 44.8% and 158% compared to the values of the alkali metal thermoelectric converter working alone and 20.5% and 80.4% when compared with a hybridized configuration including a thermoelectric energy converter.