Environmental Engineering Reference
In-Depth Information
The pre-transmission hybrid architecture is characterized by high part load
efficiency. Electric-only range requirements constrain the required battery capa-
city, as noted in Table 1.16.
In Figure 1.47 the dark area is the electric motor only (EV mode) for both
motoring and generating modes. Overlaid on this M/G capability plot is the engine
operating space in the first quadrant only. The engine torque-speed capability plot
shows three modes: (1) the hybrid-generate mode where power is delivered to both
the battery and the wheels, (2) the engine-only or CV mode and (3) the hybrid
depletion mode where the battery assists the engine to deliver high peak power for
vehicle launch, acceleration and grade climb. Note that the M/G capability extends
down to zero speed in both motoring and generating quadrants (first and fourth).
400
300
200
100
Engine-
only
0
-100
-200
Motor-
only/
hybrid
-300
0
1,000
2,000 3,000
Powertrain speed (rpm)
4,000
5,000
6,000
Figure 1.47 Overlay of engine torque-speed on M/G capability plot (courtesy
EPRI [21])
1.8.3 Charge sustaining and charge depleting
Hybrid vehicle classification H0 was described previously as a CS, parallel hybrid.
More of this will be discussed in Chapter 2. For our purposes a CS hybrid replen-
ishes its on-board energy storage system either through regenerative braking or by
running the engine driven generator when most feasible to maintain the battery
SOC between 60% and 80%.
Plug-in hybrids discussed above will have their fuel economy measured
according to SAE J1711 [22], which states that total fuel consumed during the
drive cycle is the sum of on-board fuel consumed in gallons (US) plus the fuel
equivalency of off-board supplied charge. Wall plug supplied recharge energy is
accumulated by the on-board energy storage system until its SOC matches its
initial value. This total charge in kWh is divided by the fuel equivalency
according to (1.46):
