Environmental Engineering Reference
In-Depth Information
Figure 1.38 Seals of the US DOT and EPA making the above stated comment
Consider also that EPA and DOT (Figure 1.38) want to move to g CO
2
/mi
instead of mpg, but it is effectively the same measure (for petroleum), with different
units. This generates lot of confusion by mixing electrical-energy-only miles with
petroleum-fuelled miles (Prius gets 51 mpg (EPA); Chevy Volt claims 230 mpg;
Nissan LEAF EV, 267 mpg). The public is sure to be confused as well, and as of
this date the regulating agencies are still revising the testing methods needed to
validate such manufacturer claims.
For example, subject matter experts at the US Argonne National Laboratory
are leading the team to define how fuel economy of plug-in hybrids (PHEVs)
should be measured and consider two main cases: (1) CD followed by CS with no
engine contribution during the CD mode and (2) blended mode CD followed by CS.
In the first case the vehicle operates essentially as an EV and in the second case as
an REV. Figure 1.39 [18] illustrates the differences.
'Charge-
depleting'
'Charge-
sustaining'
(Start of day)
EV
mode
Sustain mode
x
Miles EV
range
= Engine-on
'Charge-
depleting'
'Charge-
sustaining'
(Start of day)
Depleting
mode
Sustain
mode
x
Miles CD
range
Figure 1.39 Charge depleting versus charge sustaining modes [18] and volt
PHEV concept
