Environmental Engineering Reference
In-Depth Information
Fig. 6.29 Stack and fuel cell
system efficiency versus
cycle length in hard hybrid
configuration on the R47
driving cycle
Fig. 6.30 Stack and fuel cell
system efficiency versus
cycle length in soft hybrid
configuration on the R40
driving cycle
by the battery and electric drive power curves. It can be observed from Fig.
6.28
c
that two recharging steps are obtained when the electric drive operates as generator
during the second and fourth deceleration phase of the cycle.
The electric energy recovered during the regenerative braking phases can be
evaluated for both cycles, as percentage of the energy entering the electrical drive,
it results about 8 and 16% for R47 (Fig.
6.27
) and R40 (Fig
6.28
), respectively.
The instantaneous efficiency of the stack and FCS are shown in Fig.
6.29
for
R47 cycle in hard hybrid configuration and in Fig.
6.30
for R40 cycle in soft
hybrid configuration. According to the results obtained in steady-state operation,
during the low load phases the stack efficiency reaches the value of about 0.7,
whereas during the power variations required by the electric drive the efficiency
decreases down to the lowest value of about 0.6, in correspondence with the most
