Environmental Engineering Reference
In-Depth Information
application. For instance, if the dynamic requirement is not too demanding the
FCS can follow the load variation up to its maximum power, while the
assistance of batteries becomes essential when very high acceleration perfor-
mance are required by the driver. On the other hand, the hard hybrid option
assigns to batteries the task to satisfy also the fastest dynamic requirements,
but could not be able to manage the energy of batteries in not expectable
driving conditions. However, when the driving cycle is previously known, and
is characterized by an average power much lower than the cycle power peaks,
the hard hybrid configuration is preferred, because a much smaller FCS can
be adopted.
The electric energy storage system usually adopted in fuel cell power trains
consists of electrochemical batteries and/or super capacitors. The latter represent a
promising alternative to batteries, because they have an extremely high specific
power and higher charge and discharge efficiency than any types of batteries. For
these reasons super capacitors can be used to cover power peaks, especially
required during accelerations and during regenerative breaking to save the vehicle
kinetic energy.
Other configurations of fuel cell vehicles can be realized combining the
advantages of different types of storage systems. As an example, the Fig. 5.24
shows the combination of rechargeable batteries with a super capacitor system. In
this case, a three-way converter is required to connect the two storage systems with
the fuel cell stack and interface the different voltage versus current characteristics
of the devices interconnected [ 46 ].
Super CAPACITOR
H2 TANK
TRASMISSION
3 WAY
DC-DC
CONVERTER
DC-AC
CONVERTER
ELECTRIC
MOTOR
Fuel Cell
System
Electric Drive
Rechargeable
BATTERY
Fig. 5.24
Configuration of fuel cell vehicle equipped with rechargeable batteries and super
capacitors
 
Search WWH ::




Custom Search