Environmental Engineering Reference
In-Depth Information
Table 9.1 Fuel cycle upstream energy consumption and CO
2
emissions
( from Reference 5)
Fuel type
Upstream total
energy (J/MJ)
Upstream
CO
2
(g/MJ)
Gasoline
262,049
18.5
Diesel
197,654
14.1
E85 (15% gasoline, 85% ethanol)
561,759
12.2
Electricity
3,261,902
195.1
Gaseous H
2
634,356
92.0
Liquefied H
2
1,484,523
138.5
from 100% corn stock with the caveat that the US is unlikely to produce corn in
sufficient quantity to meet large scale transportation needs. Transportation fuel
consumption in North America accounts for some 40% of all energy usage. Second,
in terms of emissions of CO
2
, E85 has a negative result because in the process of
growing, corn absorbs CO
2
from the atmosphere. Third, electricity in the context of
a BEV makes sense from a TTW perspective, but clearly its upstream energy and
emissions are very significant.
Figure 9.2 summarizes the total energy scenario from primary fuel to energy
available at the vehicle's wheels in the two step process noted above: WTT
and TTW, plus a composite energy for well-to-wheel (WTW). The CIDI hybrid
vehicle has higher overall efficiency than a conventional CIDI power plant vehicle
because of the hybrid's energy regeneration capability. The same applies to the
difference noted between a conventional, or direct hydrogen, FCV versus a hybri-
dized fuel cell vehicle (FCHV).
Figure 9.2 shows that gasoline and diesel fuel have the highest WTT effi-
ciency, consistent with their production energy consumption listed in Table 9.1, but
Fuel cycle efficiency
55.9
H
2
FCHV
52
29.1
55.9
H
2
FCV
46.6
WTT
26.1
84.3
CIDI HV
31
TTW
26.1
84.3
WTW
CIDI ICE
18.5
15.6
80.6
Gasoline ICE
14.1
11.4
0
20
40
60
80
100
Efficiency (%)
Figure 9.2 Well-to-wheel energy efficiency summary (modified from Reference 4)
