Performance potential of a new molten hydroxide direct carbon fuel cell–based triple-cycle system for clean and efficient coal use

Abstract: To efficiently and environmental-friendly use coal, a novel triple-cycle system model incorporating molten hydroxide direct carbon fuel cell (MHDCFC), alkali metal thermal electric converter (AMTEC), and thermoelectric generator (TEG) is proposed to evaluate the performance potential. Considering a variety of electrochemical and thermodynamic irreversible losses, a mathematical model for the proposed system is developed, and optimum operation ranges for several important performance indicators are determined. Numerical calculations indicate that the improvements in the maximum power density and the corresponding efficiency of the triple-cycle system are, respectively, about 92% and 26% compared with the single MHDCFC, and the improvements are, respectively, 11% and 10% compared with the cogeneration system composed of MHDCFC and AMTEC. Extensive parametric studies show that an increase in the operating temperature, reactor compartment width, proportional coefficient, or thermocouple number may positively improve the tricycle system performance; whereas an increase in the O₂ flow rate, ratio of AMTEC cathode area to MHDCFC electrode area or thermodynamic loss-related parameter may degrade the tricycle system performance. Highlights: An advanced triple-cycle system is proposed for waste heat recovery. Various irreversible losses within the system are mathematically described. Optimal operation ranges for several important performance indicators are determined. Maximum power density and efficiency are increased by 92% and 26%, respectively. Effects of some important parameters on the system performance are discussed.