Multi-objective optimization and comparative performance analysis of hybrid biomass-based solid oxide fuel cell/solid oxide electrolyzer cell/gas turbine using different gasification agents

In this study, a novel configuration consisting of a biomass-based anode/cathode recycling solid oxide fuel cell integrated with a gas turbine and solid oxide electrolyzer cell is proposed for power and hydrogen production. The new configuration is modeled using Air, O₂-enriched air, O₂ and CO₂ as the gasification agents. Accordingly, the waste heat of the SOFC is exploited in the gas turbine and subsequently the generated power of the gas turbine is transferred to a solid oxide electrolyzer cell unit for hydrogen production. Consequently, the proposed system is analyzed and compared from energy, exergy and exergoeconomic viewpoints using different gasification agents through the parametric study. Subsequently, the system in which pure CO₂ is considered as the gasification agent is optimized by multi-objective optimization method based on genetic algorithm. Accordingly, the optimal solution points are gathered as four Pareto frontiers considering exergy efficiency, total product cost, levelized emissions and rate of hydrogen production as the objective functions. The results of parametric study show that the highest exergy efficiency/power production at the same time the lowest total product cost are expected for the system using O₂ as the gasification agent. On the other hand, using CO₂ as the gasification agent (by recycling 20% of the emitted CO₂ into the gasifier) leads to the highest hydrogen production rate and the lowest levelized emissions in a wide range of the effective parameters. Considering exergy efficiency and total product cost as the objective functions, the results of the multi-objective optimization indicate that, exergy efficiency and total product cost would be 45.25% and 16.21 $/GJ, respectively at the optimum operating condition. Furthermore, results of multi-objective optimization from hydrogen production rate and levelized emissions viewpoints show that the corresponding values may be 8.561 kg/h and 7.745 t/MWh, respectively.