Environmental Engineering Reference
In-Depth Information
Example 2:
An energy recuperator system is able to save 1.6% fuel consumption
on a 6 L/100 km vehicle. What will this amount of savings translate to in additional
consumer electrical loads relative to the same vehicle without a recuperator?
Assume: 1% fuel economy benefit per 120 W of electrical load.
Solution:
The wording of this example requires the reader to exercise caution in
the solution. First of all the fuel savings is stated as %FC, whereas electrical
load burden is stated as %FE
benefit
. Using (1.34) we obtain
%FC
benefit
100
%FC
benefit
1
:
6
100
1
:
6
%FE
benefit
¼
100
¼
100
¼
1
:
626%
Therefore, 1.626%FE
benefit
translates to (1.626/1.0)120 = 195 W of additional
electrical load. This, for example, is sufficient to power all external lights on the
vehicle.
2.2.2 Micro hybrid
Micro hybrid represents the next level in vehicle electrification and is advertised
and sold variously as idle-stop or auto-stop, or in the case of General Motors as belt
alternator starter (BAS). The concept is the same, not only recuperating and storing
vehicle braking energy but also eliminating fuel consumption during engine idle.
The tier-one supplier Valeo in France markets such systems under the trade name
StARS (Starter-Alternator Reversible System) where the primary function is that
of a power electronic enabled reversible alternator as described in Reference 14 and
illustrated in Figure 2.10. In this system the alternator can operate unregulated
to 14 +
x
volts (typically
x
~ 20 V) and it provides sufficient motoring torque
(~50 Nm) to restart 2.0 L gasoline, or 1.6 L diesel engines. With an ultra-capacitor
accumulator, the StARS +
x
system can regenerate to 5 kW and supply up to 4 kW
to the vehicle EDS.
Starter-alternator
reversible system
control unit
12 V bordnet
DC
DC
High power
electrical loads
12 V battery
Ultra-capacitor
Figure 2.10 Micro hybrid reversible alternator system
