Combined systems based on OSOFC/HSOFC: Comparative analysis and multi-objective optimization of power and emission

An integrated system, including a biomass gasifier, a solid oxide fuel cell, heat pipes, and an organic Rankine cycle, was modeled and validated. The system performance was assessed in two different cases based on: (a) oxygen-ion conducting electrolyte and (b) proton-conducting electrolyte solid oxide fuel cells. At low current densities, the system based on proton-conducting electrolyte cell presented larger values of power. In contrast, the system based on oxygen-ion conducting electrolyte cell had a better performance from power viewpoint at high current densities. This phenomenon was similar for energy and exergy efficiencies and emission. The comparative analysis revealed that the system based on oxygen-ion conducting electrolyte cell had higher power output than the system based on proton-conducting electrolyte cell (204.2 kW against 178.7 kW) at their optimum conditions, while the system based on proton-conducting electrolyte cell presented lower emission (996.5 kg/MW h against 1560.7 kg/MW h). The TOPSIS method was utilized to solve the multi-criteria decision-making problem. The results indicated that the system based on proton-conducting electrolyte cell had a better performance than the system based on oxygen-ion conducting electrolyte cell.