Environmental Engineering Reference
In-Depth Information
Fig. 6.25 Stack power and
air flow rate profiles versus
time during a R40 cycle and
b R47 cycle
limiting the DC-DC converter output current. The two values of power are chosen
equal to 900 and 450 W, corresponding to the two phases of the cycle at constant
engine speed. The motor power (Fig.
6.27
a) reaches its highest value (3500 W)
during the first acceleration phase, then decreases up to 1200 W corresponding to
the first step at constant motor speed, finally decreases up to negative power values
during the deceleration phase, when the electric machine operates as generator. At
the end of this deceleration, the motor power reaches the second phase at constant
speed (220 W), followed by the last deceleration phase up to zero speed.
The battery power curve shows that the storage system plays the role of
compensating the difference between the motor power requirements and power
supplied by the fuel cell system (Fig.
6.27
a). In particular, the electric energy
flowing from the battery pack permits the motor power peak to be satisfied,
whereas during the regenerative braking, when the electric machine is operating as
