Research On Transient Performance Of High Temperature Proton Exchange Membrane Fuel Cells

In the applications of fuel cells, the lower temperature proton exchangemembrane fuel cells (PEMFC) are suffering from great challenges such as thedifficult water management and the poisoning effect of carbon monoxide (CO). Thehigh temperature PEMFC goes into people’s vision due to its better watermanagement (no accumulation of liquid water at high temperature above100℃) andhigh tolerance for CO. Based on the real application of high temperature PEMFC, thispaper studies the transient response of high temperature PEMFC under differentoperating conditions.In this work, a three-dimensional non-isothermal transient model of hightemperature PEMFC with phosphoric acid doped PBI membrane is developed toanalyze the influence of different external conditions on the current density of the cell.The paper firstly introduced the physical model and the corresponding mathematicalmodel. In the mathematical model, the effects of phosphoric acid doping level, inletrelative humidity, and the operating temperature on the membrane conductivity areconsidered. Therefore, the effects of these aspects on the transient response of cellperformance are discussed.The results show that when the reactants supply is enough, the transient responsefor sudden change of voltage is very fast. However, when the molar concentration ofoxygen is not enough, the transient response will be lower. The cell will reach to anew steady state much faster under larger voltage and lower relative humidity whenthe load changes. On the other hand, when the surrounding temperature changessuddenly, the time to a new steady state will become shorter for cells with membranesof larger phosphoric acid doping level, and cells with lower loads. When the relativehumidity is high, the second undershoot may occur. The higher the relative humidity,the higher undershoot will be found. When the inlet gas pressure increases, the cellwill reach to a new steady state much more quickly under the lower phosphoric aciddoping level, the lower inlet relative humidity, or the larger voltage. When thehumidity level is much higher, the current density will increase to a large value. Theeffects of temperature on the inlet gas pressure mutation are different according tovariation of the inlet gas pressure.