Improving Durability and Increasing Power Density by Optimizing Anode Split in a PEM Fuel Cell.
Publication Date: 2004-May-25
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Improving Durability and Increasing Power Density by Optimizing Anode Split in a PEM Fuel Cell. Also, relating to fuel starvation and reactant utilization.
IMPROVING DURABILITY AND INCREASING POWER DENSITY BY OPTIMIZING ANODE FLOW SPLIT IN A PEM FUEL CELL
The operating efficiency of a PEM fuel cell is proportional to the reactant fuel utilization. Fuel utilization is the ratio of fuel consumed to the total quantity of fuel supplied. While it is desired for efficiency reasons to operate at very high utilization of nearly 100%, it is unfeasible to do so on a practical basis. Because of durability requirements, it is a must that fuel be distributed so that every section of the fuel cell receives sufficient fuel and is not locally starved. If a cell were designed to operate at near 100% utilization, then factors such as manufacturing tolerances could result in some portions of the cell not receiving the amount of fuel it was designed for. If this happens, such localized fuel starvation causes the cathode catalyst layer to corrode and subsequently limits the maximum utilization practically achievable in a fuel cell.
In order to alleviate localized starvation, the fuel cell assembly contains a multi pass approach. With such an arrangement the total fuel utilization can be realized as high as 99%, with nominal fuel cell stack assembly utilization at 80% and individual passes in the anode operating at 60-70% utilization. Figure 1 represents the fuel reactant passes so as to have the lowest per pass utilization which increases the margin on localized starvation and improves durability. Alternatively the margin can also be used in ha...