First Name | Jeff |
---|---|
Last Name | Gonder |
Email Address | jeff_gonder@nrel.gov |
Affiliation | NREL |
Subject | Zero-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 Name | CARB15DayCommentAttachments.zip |
Date and Time Comment Was Submitted | 2008-08-14 09:48:15 |
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