Characteristics of an indirect-methanol fuel cell system

This paper discusses the various system interactions that can affect the efficiency and dynamic performance of an indirect methanol fuel cell system. The characterization of the load following IMFC system is done using the simulation model developed by the Fuel Cell Vehicle Modeling Program at the University of California-Davis. The first part of the paper briefly describes the components within the UCD-IMFC system model. The second part of the paper gives a qualitative look at the system interactions and their impact on the efficiency and dynamics of the system. There are two primary interactions within the IMFC system that are of interest. These two interactions are the fuel processor/stack interaction and the air supply/stack interaction. With respect to the fuel processor/stack anode interaction, we find a trade-off between going to a higher anode hydrogen utilization to maximize efficiency and going to a lower utilization to avoid starving the stack of hydrogen during heavy dynamic loads on the system. On the air supply/stack cathode interaction, we find that dynamics are not as much of an issue and the best operating method is one where the net power output of the stack/compressor combined is greatest for a given partial pressure of oxygen. This gives the highest efficiency for a given cathode/air supply combination. Finally, when considering the water and thermal management (WTM) of the system, we look at methods to reduce the total parasitic load on the satisfying the thermal requirements and maintaining water self-sufficiency.