Simulated Performance of an Indirect Methanol Fuel Cell System

A detailed simulation of a load-following indirect methanol fuel cell (IMFC) system was performed by the University of California - Davis fuel cell vehicle modeling program (FCVMP) in order to determine the realistic steady-state and dynamic performance of such a system. The first part of the paper includes a basic description of the model and the control of the system. The interaction between the fuel processor and the anode side of the stack is shown to have dynamic load following limitations and a subsequent control strategy is described to solve this problem. The interaction between the air supply, the cathode side of the stack and the water recovery is shown to have several optimization opportunities.

In the second part of the paper, we find that the steady state efficiency of the system peaks at approximately 52% at around 5% of full power. The 25% of full power steady-state system efficiency is approximately 45% and the full power efficiency is approximately 27%. This compares with the DOE goals for an IMFC system of 48% and 38% respectively. To determine the dynamic efficiency that could be expected from a load-following IMFC system, simulations were performed over the relatively anemic FUDS and then the more aggressive US06 drive cycles. Additionally, for each drive cycle, an expected steady state efficiency is calculated. The expected steady state efficiency is the efficiency of the system over the cycle assuming it could operate along the steady state efficiency curve. The FUDS simulation gives a dynamic cycle efficiency of 43% vs. an expected steady-state efficiency of 47%. The US06 gives a dynamic cycle efficiency of 37% vs. an expected steady-state efficiency of 43%. We find the discrepancy between the expected steady state and actual dynamic efficiencies is primarily attributed to the fuel processor.