Thermodynamic design, evaluation, and optimization of a novel quadruple generation system combined of a fuel cell, an absorption refrigeration cycle, and an electrolyzer

Abstract

In this article, a solid oxide fuel cell system is combined with a generator absorber heat exchanger absorption refrigeration cycle and a proton exchange membrane electrolyzer unit to use most of the fuel energy and recover waste heat and material. This quadruple-generation system produces electric power, refrigeration, heating, and hydrogen from natural gas as the primary energy source for the system. The thermodynamic and environmental performances of the system are studied comprehensively to identify the effects of the key operating parameters on the system operation. The results show that as fuel cell current density increases from 2000 to 8000 A/m2; the system energy and exergy efficiencies decrease by nearly 20%, but the unit carbon dioxide emission increases by 30.38%. Also, the energy and exergy efficiencies are maximized, and the unit carbon dioxide emission is minimized at a specified value of fuel utilization factor. Additionally, increasing the steam to carbon ratio has a damaging effect on the system efficiencies but leads to higher unit carbon dioxide emission. Then, the genetic algorithm is applied to optimize the condition, so the highest exergy efficiency is attainable. The optimization results demonstrate that an exergy efficiency as high as 0.6443 is achievable.