Environmental Engineering Reference
In-Depth Information
Fig. 7.54 C
v
profiles versus
cycle length for the experi-
ment of Fig.
7.53
3
2,5
2
1,5
1
0 0 0 0 0 0 0 0 0 0
Time, s
1,2
1
0,8
0,6
0,4
0,2
t=0
t=10 s
t=25 s
t=35 s
t=55 s
0
1 5 9 1317212529333741454953576165697377
Cell number
Fig. 7.55
Individual cell voltage for five significant instants of the experiment of Figs.
7.53
and
7.54
indicator is reported versus time for the entire cycle. The first peak at about 2.5
reproduces that observed in Fig.
7.52
, while the second peak at about 2.8% is due
to the second acceleration step, and is associated with incoming difficulties of air
feeding encountered by some cells. This is better evidenced by the results of
Fig.
7.55
, where the acquisitions of all individual cells are reported for initial and
final instants (t = 0 and t = 55 s), for the two C
v
peaks (t = 10 and t = 35 s) and
for the relative minimum between the two C
v
peaks (t = 25 s) which corresponds
to the initial instant of the second acceleration step. It is evident that the problem
of the last section of the stack regarding the air feeding capabilities, in particular at
t = 10 and t = 35 s, while at t = 25 s a partial voltage recovery is observed, due
to the major oxygen availability during the first stationary phase.
The results reported above show that the compressor management strategy
adopted during the dynamic operations tested clearly affects both individual cell
voltage regularity (and then stack reliability) and FCS efficiency. In fact, although
