Environmental Engineering Reference
In-Depth Information
last 100,000 mi and not be replaced by the customer in terms of operating costs. For
electric-only range the battery pack is assumed capable of 1,750 deep cycles.
A grid connected hybrid biases fuel consumption to electricity only when the
battery SOC is high, but switches automatically to hybrid mode (engine plus
electric) when (1) battery SOC is low, (2) higher vehicle loads are demanded and
(3) the driver demands full power [21]. Figure 1.45 illustrates the powertrain cap-
ability when both engine and electric systems are combined in the plug-in hybrid.
450
Engine enrichment
400
350
300
Motor
250
200
150
100
Engine
50
0
0
1,000
2,000 3,000
Powertrain speed (rpm)
4,000
5,000
6,000
Engine max torque
Engine IOL torque
Total torque
Engine IOL + Motor torque
Figure 1.45 Combined HEV powertrain torque-speed profile ( from Reference 16)
The efficiency path for hybrid powertrains is illustrated in Figure 1.46. During
engine-only operation, the efficiency path from well to wheel takes the upper path in
Figure 1.46. When electric-only mode is active, the efficiency path takes the right-
hand portion of the lower path. In combined mode with both engine and electric
modes active, the efficiency path follows the full lower portion of Figure 1.46.
Fuel
processing
(
h
= 81.5%)
Clutch
Engine
(
h
= 33%)
Fuel
(at well)
to
Transmission
Batt.
rechg.
(
h
=
96%)
Electric
motor
(
h
= 90%)
Batt.
dischg.
(
h
=
96%)
Electric
motor
(
h
= 90%)
Engine
(
h
= 32%)
Figure 1.46 Efficiency paths for hybrid powertrain (well to wheels) (courtesy
EPRI [21])
