Hybrid vehicles - Propulsion Systems for Hybrid Vehicles - page 55

Testing of charge sustaining (CS) HEV mode is performed such that any stored
electrical energy contribution to range is minimal. In fact, the guideline (1.45) is
that this charge balanced energy be < 1% of the cycle fuel energy, W cyc :

j W cyc Ah U oc j< 0 : 01 W cyc ð 1 : 45 Þ

The result of (1.45) is depicted in Figure 1.40 to illustrate that at the comple-
tion of the cycle the SOC of the RESS is approximately the same as its initial value.

60 0.5

0.4

50

0.3

0.2

Ah

40

0.1

0

30

−0.1

20

−0.2

− 0.3

10

− 0.4

0 0.5

1,400

−

400 1,200

0 200 600 800 1,000

Figure 1.40 Charge sustaining operation of the hybrid electric vehicle

Example 5: A passenger car having a fuel consumption rating of 8.55 L/100 km is
driven 9,000 mi/year on gasoline fuel. Compute the annual CO 2 emissions from
this commuter vehicle assuming the engine is operating normally and the stoi-
chiometric combustion of gasoline (density of 0.74) is 3.14 g CO 2 /kg fuel.
Solution: This example contains several unit conversions in order to complete the
calculation. The conversion of fuel consumption to fuel economy (US gallons) is
given in (1.31) from which 8.55 L/100 km ? 27.5 mpg. The vehicle will therefore
consume 9,000 mi/27.5 mpg ? 327.27 gallons of gasoline annually. For the given
density and knowing there are 3.785 L/gallon leads to (0.74 kg/L)(3.785 L/gallon) =
2.801 kg/gallon of gasoline. Therefore, using the stoichiometric production of CO 2
per kg of gasoline leads to (3.14 kg CO 2 /kg gasoline)(2.801 kg gasoline/gallon)
(327.27 gallon/year) = 2878 kg CO 2 /year!
In this example the commuter vehicle emits some 2.88 ton CO 2 /year.