Jc. Amphlett et al., A MODEL PREDICTING TRANSIENT RESPONSES OF PROTON-EXCHANGE MEMBRANE FUEL-CELLS, Journal of power sources, 61(1-2), 1996, pp. 183-188
There has been a recent interest in modelling the transient behaviour
of proton exchange membrane (PEM) fuel cells. In the past, there have
been several electrochemical models which predicted the steady-state b
ehaviour of fuel cells by estimating the equilibrium cell voltage for
a particular set of operating conditions. These operating conditions i
ncluded reactant gas concentrations and pressures, and operating curre
nt. Steady-state behaviour is very common and in some cases is conside
red as the normal operating standard. Unsteady-state behaviour, howeve
r, is becoming more of an issue, especially for the transportation app
lications of fuel cells where the operating conditions will normally c
hange with time. For example, system start-up, system shut-down, and l
arge changes in the power level may be accompanied by changes in the s
tack temperature, as well as changes in the reactant gas concentration
s at the electrode surface. Therefore, both mass and heat transfer tra
nsient features must be incorporated into an electrochemical model to
form an overall model predicting transient responses by the stack. A t
hermal model for a Ballard Mark V 35-cell 5 kW PEM fuel cell stack has
been developed by performing mass and energy balances on the stack. T
he thermal characterization of the stack included determining the chan
ges in the sensible heat of the anode, cathode, and water circulation
streams, the theoretical energy release due to the reaction, the elect
rical energy produced by the fuel cell, and the heat loss from the sur
face of the stack. This thermal model was coupled to a previously-deve
loped electrochemical model linking the power produced by the stack an
d the stack temperature to the amount and method of heat removal from
the stack. This electrochemical model calculates the power output of a
PEM fuel cell stack through the prediction of the cell voltage as a c
omplex function of operating current, stack temperature, hydrogen and
oxygen gas flowrates and partial pressures. Initially, a steady-state
overall dynamic model (electrochemical model coupled with the thermal
model) was developed. This was then transformed into a transient model
which predicts fuel cell performance in terms of cell voltage output
and heat losses as a function of time due to various changes imposed o
n the system.