Analysis of Flow Errors and Resulting Stoichiometry Uncertainties while Using a Fuel Cell Stack Test Station for Reactant Delivery and Control.

This paper communicates our work on the analysis of difficulties with and limitations of proper delivery of reactants to a fuel cell system that are the result of statistical uncertainties of settings of individual control and measurement devices in the control system. We attempt to set a statistics based groundwork for estimating uncertainties in actual fluid flow in fuel cell stack relative to desired flow set points, stoichiometries and size. Although only the fuel side of the test station that is particularly poorly matched to its test subject is analyzed in the presented example, the method is equally applicable to any control systems and to other pertinent fluids. Similar analysis can and should be performed during design stages of any control scheme for fuel cell systems. This work is most pertinent for (and was a direct response to challenges associated with) stack operation under extremely low stoichiometry conditions.