
210 Fuel Cells
η
αα
=−
+
−
+RT
F
jj
j
RT
F
jj
Ox,a
extloss
aRed,c
extlos
ln ln
0
ss
c
econ extiextloss
La
La
j
rr jrjj
RT
nF
j
j
0
−+ −+
−
()
ln
−−−
+
−−
jj
RT
nF
j
jj j
extloss
Lc
Lc extloss
ln
.
(5.153)
The kinetic losses, ohmic losses, mass transfer losses, and short circuit and
crossover losses are illustrated in Figure 5.27. The dominant losses are typi-
cally activation losses and ohmic losses. At high current density, the mass
transfer or concentration losses dominate. In the illustration, the internal
losses are shown as constant; however, the internal losses also depend on the
current density.
The fuel cell voltage E is thus the difference between open-circuit vol ...