Thermodynamic analysis of production of hydrogen using high-temperature fuel cells

This paper presents: (1) the electricity and hydrogen co-production concept, (2) a thermodynamic analysis methodology for studying solid oxide and molten carbonate fuel cell hydrogen co-production, and (3) simulation results that address the impact of reformer placement in the cycle on system performance. The methodology is based on detailed thermodynamic and electrochemical principles that apply to each of the system components and the integrated cycles. Eight different cycle configurations that use fuel cell heat to drive hydrogen production in a reformer are proposed, analyzed, and compared. The specific cycle configurations include SOFC and MCFC cycles using both external and internal reforming options. The fuel cell plant performance has been evaluated on the basis of methane utilization efficiency and each component of the plant has been evaluated on the basis of second law efficiency. The analyses show that in all cases the exergy losses (irreversibilities) in the combustion chamber are the most significant losses in the cycle. Furthermore, for the same power output, the internal reformation option has the higher electrical efficiency and produces more hydrogen per unit of fuel supplied, in the case of using a SOFC.