Bi-objective optimization of biomass solid waste energy system with a solid oxide fuel cell.

Thesolid oxide fuel cell (SOFC), as an economically friendly power generation system, shows a promising prospect for the future while hydrogen supply as its fuel is one of the main challenges. In this paper, an integrated system is described and evaluated by energy, exergy, and exergoeconomic, aspects. To find an optimum design state three models were analyzed to reach higher energy and exergy efficiency while system cost is at its lower value. After the first and main models, a Stirling engine reuses the first model's waste heat to generate power and enhance efficiency. In the last model, a proton exchange membrane electrolyzer (PEME) is considered for hydrogen production purposes by using the surplus power of the Stirling engine. The components validation is performed in comparison with the data presented by related studies. Optimization is applied by exergy efficiency, total cost, and hydrogen production rate considerations. The results show that the total cost of the model (a), (b), and (c) is 30.36 ($/GJ), 27.48 ($/GJ), and 33.82 ($/GJ), and the energy efficiency is 31.6%, 51.51%, 46.61% and the exergy efficiency is 24.07%, 33.0.9%, 29.28% respectively with the cost of at the optimum condition achieved by 2708 A/m current density, 0.84 utilization factor, 0.38 recycling anode ratio, 1.14 air blower and 1.58 fuel blower pressure ratio. The optimum rate of hydrogen production will be 138.2 kg/day and the overall product cost will be 57.58 $/GJ. In general, the proposed integrated systems show a good performance in both thermodynamics and environmental and economic aspects.