System simulation and exergetic analysis of solid oxide fuel cell power generation system with cascade configuration

摘要

A solid oxide fuel cell (SOFC) based power generation system with cascade configuration has been analyzed using the exergy-based analysis method.A cascade system has double SOFC stacks,where the unreacted fuel released from the primary SOFC stack is re-utilized in the secondary stack,generating additional power and maximizing fuel-use in the system.For comparison and evaluation,a simple SOFC system and an SOFC system with anode off-gas recirculation are also analyzed.In all the SOFC systems,efficiency increases with increasing fuel utilization.The simple and anode off-gas recirculation systems show 63.7% and 66.0% electrical efficiency at 85% and 90% fuel utilization,respectively.The cascade system shows 66.47% electrical efficiency at 90% fuel utilization,which is the highest electrical efficiency among the systems analyzed.Through the exergy analysis,the magnitude,location,and resources of the thermodynamic irreversibility within the SOFC systems are clearly identified,giving the quantified information why the cascade configuration has higher efficiency than the other configurations.The SOFC stack shows very high exergetic efficiency over 90%.In the cascade configuration,the released exergy from the primary SOFC stack can be exergetically-efficiently utilized in the secondary SOFC stack,contributing to a higher efficiency.