PEM 燃料電池動態響應時間常數之理論與實驗研究(1/3)

The dynamic performance of PEM fuel cells is one of the most important criteria in the
design of fuel cells with application to mobile systems. To study this issue, we extend our
previous steady model of gas reactant transport to an unsteady one and employ it to examine
the transient transport characteristics and the system performance of the PEM fuel cells. With
the assumption of the two-dimensional mass transport in the cathode side of PEMFC, the
effects of the channel width fraction, λ = lc/lb, the porosity of the gas diffuser layer, 1 ε ,
and the surface over-potential of the catalyst layer, η , on the transient characteristics of the
resultant current density and mass transport are focused in this work. It is disclosed that an
increase in λ , or η may lead to a faster dynamic response for the fuel cell when the PEM
fuel cell system is started up. Results of a typical case demonstrate that, although the dynamic
response time may be as long as 10 s due to the mass transport lag, the fuel cell system needs
only less than 0.4 s to reach the 90% response.