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Comment 43 for ZEV 2008 (zev2008) - 15-1.

First NameJeff
Last NameGonder
Email Addressjeff_gonder@nrel.gov
AffiliationNREL
SubjectZero-Emission VMT PZEV Allowance Recommendations
Comment
These comments fall along the same line as my earlier e-mail
(included in the attached zip file).  They are updated and
summarized below with reference to the equations in section C-3.3
(pp. C-11 and C-12) in the 15-day notice (7/25/08) version of the
"California Exhaust Emission Standards and Test Procedures for
2009 and Subsequent Model ZEVs, and 2001 and Subsequent Model
HEVs, in the Passenger Car, Light-Duty Truck and Medium-Duty
Vehicle Classes."  The second file in the zipped attachment is an
updated version of the spreadsheet I included previously that now
uses the updated equation as well as alternate versions exploring
replacement of UF(R_cda) with UF(EAER) or UF(R_cdc) (read "utility
factor as a function of xyz").  The two parameters that can again
be varied on the spreadsheet are the miles offset between the
whole-cycle charge-depleting range measurement and the "actual"
charge-depleting end point (R_cdc – R_cda), and the equivalent
electric range fraction (EERF).  The "_Example1" tab (with Offset
= 4 and EERF = 0.5) highlights the allowance discontinuity at 40
miles R_cda for the cases taking the UF of R_cda or R_cdc.  The
"_Example2" tab (with Offset = 6 and EERF = 0.9) demonstrates the
mathematical possibility to exceed the 1.35 peak allowance
(intended for long R_cda distances) at actual R_cda values
slightly less than 40 miles for the case taking the UF of R_cda. 
Here is a summary of my observations and recommendations based on
this examination:

1) It is confusing to now use a mixture of EAER and R_cda to
define whether the allowance is a constant or derives from the
equation.  For instance, it is possible to have an EAER of 10.1
miles and an R_cda of 9.9 miles which presents a circumstance
undefined by the table in section C-3.3.  ***In addition, because
the peak allowance is now defined by R_cda, a manufacturer could
simply include enough battery energy to displace the minimum 10
miles worth of CO2 production and slowly deplete it over 40+ miles
in order to earn the maximum credit (see "_Example1" using
progressively smaller EERF).***  This would be a cost-effective
way for a manufacturer to maximize credit earnings, but would not
provide the large CO2 displacements desired.  RECOMMENDATION:
Return to range bins defined solely by EAER.
2) It is also confusing as written to understand what the maximum
allowance should be.  Is the "EAER_40" supposed to be a variable
or a constant?  RECOMMENDATION: Re-write the maximum allowance as
40/29.63 or 1.35 if that was the intention.
3) R_cda is a somewhat abstract variable compared to EAER, which
is calculated from the full R_cdc measurement multiplied by the
measurable CO2 offset fraction (EERF).  It's application is
further brought into question by the two examples shown in the
spreadsheet, and by the fact that a fractional distance into a
cycle may not correspond to an equivalent fractional energy use or
CO2 production.  RECOMMENDATION: Simplify the regulation by
eliminating the need for R_cda measurement and instead of using
UF(R_cda) in the equation:
A) Use UF(EAER) if the intent is just to have an asymptotically
increasing credit with no discontinuity, or
B) Use UF(R_cdc) if the intent was to give less credit to vehicles
with lower EERF (but avoid potential "gaming" aimed at maximizing
the 'Offset' that I have defined in the spreadsheet in order to
exceed the intended peak credit of 1.35).

Please let me know if you would like me to clarify or discuss any
of these comments further.

Regards,

Jeff Gonder
Center for Transportation Technologies and Systems (CTTS)
National Renewable Energy Laboratory (NREL)

Attachment www.arb.ca.gov/lists/zev2008/2517-carb15daycommentattachments.zip
Original File NameCARB15DayCommentAttachments.zip
Date and Time Comment Was Submitted 2008-08-14 09:48:15

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