Environmental Engineering Reference
In-Depth Information
Fig. 6.32 Soft hybrid procedure during R40 cycle on fuel cell scooter. a electric energy profiles
instantaneously exchanged by electric drive, battery pack, and FCS with the electric bus versus
cycle length. b histogram of individual cell voltage at three instants during the third acceleration
phase of the R40 cycle
into account the amount of energy needed to level the initial and final SOC for
both the tests.
The fuel cell system efficiency results slightly higher for the hard hybrid pro-
cedure (g
FCS
= 0.51) than soft hybrid (g
FCS
= 0.48). According to the above
discussion, during the hard hybrid test the stack is controlled to operate in a fixed
working point, corresponding to the highest FCS efficiency, whereas during the
soft hybrid experiment the stack is left free to follow the load variations, then the
fuel cell system for some periods of the cycle works in a condition of low effi-
ciency. The DC-DC converter efficiency in hard hybrid results slightly higher
(g
DC
= 0.87) than the value obtained for soft hybrid (g
DC
= 0.80), because of
