# Air Resourc,es Board Mary D. Nichols, Chairman

9480 TelstarAvenue, Suite 4 Matthew Rodriquez Secretaryfor EnvironmentalProtection El Monte, California 91731 •www.arb.ca.gov Edmund G. BrownJr.

December 29, 2014

Mr. Matthew Spears Center Director U.S. Environmental Protection Agency 2000 Traverwood Drive Ann Arbor, Michigan 48105

Dear Mr. Spears: Governor

I am writing to request thatthe U.S. Environmental Protection Agency (U.S. EPA) require a mandatory supplemental check for oxides of nitrogen (NOx) emissions for hybrid vehicles in the Phase 2 Greenhouse Gas (GHG) Standards, scheduled for proposal next spring. This letteroutlines the reasons whytheAir Resources Board (ARB) is concerned.about possible excess NOx emissions from hybrid vehicles and howwe propose preventing such excess emissions. ARB estimates that an additional 90 percent reduction in the NOx emission standard is needed from heavy dutydiesel engines in orderto attain federal ambient airquality standards in the South Coast and San Joaquin air basins in 2032. 1 Hence, California needs to ensure thatthe Phase 2 standards not only do not result in increased**N~** emissions, but position us to collaboratively pursue lower NOx standards once the Phase 2 standards are finalized. This is especially important as we expect additional non-attainment areas nationwide will also be pressed to achieve more NOx reductions oncethe new, more stringentfederal ozone standard is promulgated. Background ARB strongly supports the development and deployment of heavy-duty hybrid vehicles and sees heavy-duty hybrid technology as a key stepping stone toward meeting California's airquality and climate goals. In fact, through California's Hybrid and ZeroEmission Truck and Bus Voucher Incentive Project, ARB has provided funding for nearly 1,500 heavy-duty hybrid vehicles overthe pastfouryears. In addition to hybrid technologies' potential fuel economy improvements and airquality benefits, ARB staff

1ARB and the South CoastAirQuality Management District areworking to refine the estimate of emission reductions needed as part ofthe 8-hour ozone plan dueto U.S. EPA in 2016.

The energychallenge facing California is real. Every Californian needs to take immediate action to reduce energyconsumption. Fora listofsimple waysyou can reduce demandandcutyourenergycosts, see ourwebsite: http://www.arb,ca.gov. California Environmental Protection Agency
Printedon RecycledPaperMr. Matthew Spears December29, 2014 Page 2
expects hybrids to play a substantial role in further advancing the development of battery and electric drive components that are needed for heavy-duty near-zero and zero-emission vehicles. As discussed below, in orderto achieve theirfull emission reduction potential, it is necessaryforthe hybrid system to be fully integrated with the vehicle's engine and emissions after-treatment systems. Heavy-duty hybrid vehicles with greaterthan 14,000 pounds gross vehicle weight rating are required to be equipped with a certified engine and onboard diagnostic systems that monitor both the engine and hybrid systems and notifythe operator ifan issue exists with the emission control system. While the engine is the only part ofthe system currently tested for emission compliance under certification, it is obvious thatthe hybridization ofthe vehicle which manipulates the performance ofthe engine can lead to emission profile changes. Hybrid technologies for heavy-duty diesel vehicles have been demonstrated to reduce fuel consumption when compared to conventional diesel vehicles. In addition, ifthe hybrid system is well designed and integrated, NOx emissions from a hybrid vehicle can also be lower compared to a comparable conventional vehicle. However, ifthe hybrid system was insufficiently integrated to the vehicle's engine and emissions aftertreatment systems, hybrid vehicles can have significantly higher NOx emissions compared to conventional vehicles2

. To ensure the NOx performance of heavy-duty hybrid vehicles and better supporttheir development and deployment, ARB developed voluntary certification procedures, "California Interim Certification Procedures for2004 andSubsequentModelHybl'{dEiectric and OtherHybrid Vehicles in the Urban Bus andHeavy-Duty Vehicle Classes", which were adopted in 2002 and amended in 2013. ARB's voluntary certification procedures were designed for heavy-duty hybrid vehicle manufacturers seeking voluntary vehicle-based certification using a chassis dynamometer. The voluntary procedures provide for the determination ofa NOx certification value for a hybrid vehicle using a ratio method ofchassis dynamometertest results ofthe hybrid vehicle and a comparable conventional baseline vehicle. The certification value for a heavy-duty hybrid vehicle is determined through calculations using chassis dynamometertest results and engine certification values for both the hybrid vehicle and a comparable conventional vehicle. Chassis testing is done using two defaultduty cycles, including the Orange County Bus Cycle and the Heavy-Duty Urban Dynamometer Driving Schedule (UDDS), one ofwhich can be replaced with anothertest cycle thatthe certifying party believes to be more representative ofthe specificvocational duty cycle thatthe hybrid vehicle will see.

2 Data Collection, Testing, and Analysis of Hybrid ElectricTrucks and Buses Operating in California Fleets, Final Draft, May 2014Mr. Matthew Spears December29, 2014 Page 3



### Recommendations To address the potential NOx emission increases for heavy-duty hybrid vehicles discussed above, we recommend a mandatory supplemental checkfor NOx emissions for all hybrid vehicles used to meetthe Phase 2 standards. Hybrid vehicles should be required to confirm compliance to current NOx emission standards using the supplemental check, as illustrated in the Attachment. We recommend using the ratio method included in ARB's "California Interim Certification Procedures for2004 andSubsequentModelHybrid-Electric and Other Hybrid Vehicles in the Urban Bus andHeavy-Duty Vehicle Classes." ARB's certification procedures specifically require the use ofchassis dynamometertesting. To allow additional flexibility, ARB staff recommends allowing powertrain testing, as described in 40 Code of Federal Regulations 1037 as an option to chassis dynamometertesting. We recommend that the Orange County Bus Cycle or UDDS cycle be used, along with anothertest cycle thatthe certifying party believes to be more representative ofthe specific vocational duty cycle ofthe hybrid vehicle.3
We recognize that requiring the recommended supplemental check will add costto hybrid manufacturers. In 2013, staffsurveyed three vehicle chassis test laboratories and estimated thatthe total testing costs is approximately $30,000 pertestvehicle or hybrid engine family, excluding testvehicle pick-up and delivery service. Some hybrid manufacturers may have difficulties accessing chassis or powertrain testtime fortheir vehicles due to the limited availability oftestfacilities. ARB's research and discussions with stakeholders found 11 chassis dynamometerand 5 powertrain test cell

**sites~n** North America. Most ofthe test sites are for research and in-house use only. We are recommending two possible approaches to address testing cost and accessibility issues mentioned above:



### • Do not makethe supplemental check mandatory ifvehicle manufacturers can demonstrate compliancewith the Phase 2 carbon dioxidefleetaverage (g/ton-mile)without counting the contribution from their hybrid vehicles. This would remove the possibility of Phase 2 standards incentivizing manufacturers to build hybrids that ultimately increase NOx. For manufacturers not counting hybrid vehicles toward the Phase 2fleet averages, in lieu ofthe supplemental check, U.S. EPA could require submittal ofemission test data

3 A hybrid vehicle manufacturerthat is planning to measure hybrid vehicle C02 using the ARB transient test cycle on a powertrain test could satisfy the requirement for a supplemental NOxcheck by measuring NOx during the ARB transienttest, powertrain testing their hybrid vehicle for NOxon either the UDDS or Orange County bus cycle, and then powertrain testing a conventional diesel vehicle for NOx on both test cycles forA to B comparison purposes.Mr. Matthew Spears December29, 2014 Page4**-~------**

indicating NOx emissions are acceptable via another method, for examplefrom Portable Emission Measurement Systems (PEMS) testing; or

• Require a supplemental check confirming compliance to current NOx · standards only for high-volume manufacturers of hybrids. U.S. EPA could require the supplemental check onlyfor manufacturers with projected or actual combined national sales of heavy-duty hybrid vehicles ofsome de minimis amount, for example, 500 units peryear. For lower-volume manufacturers of hybrids, in lieu ofthe supplemental check, U.S. EPA could require submittal of emission test data indicating NOx emissions are acceptable via another method, for examplefrom PEMS testing. ARB staffbelieves that including this supplemental cheQk for NOx emissions in Phase 2 rule is an important element in avoiding NOx increases for heavy-duty hybrid vehicles. This procedure would provide manufacturers flexibility and a more straightforward mechanism to certify hybrid vehicles. It would also encourage manufacturers to further deveiop advanced technologies. Ifyou have questions or need additional information, please contact Ms. Kim HeroyRogalski, Manager, at (916) 327-2200, or email at kheroyro@arb.ca.gov or me at (626) 575-6632, or email at mcarter@arb.ca.gov. Sincerely, .) (\

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### .~~**v~fl/J!lAJ~~J** Michae Carter, Chief Mobile Source Regulatory Development Branch California Air Resources Board Attachment
cc: JamesTamm Fuel Economy Division Chief National HighwayTraffic SafetyAdministration Annette Hebert, Division Chief Emissions Compliance, Automotive Regulations and Science Division Kim Heroy-Rogalski, Manager Strategic Planning & Development Section 

### \Mr. Matthew Spears December29, 2014 Attachment Example ofCertification by Emission Factor Ratio Application Example 1

- Forexample, manufacturerXYZ produces heavy-duty hybridelectric buses and performs chassis dynamometertesting with the following data: Hybrid-electric Bus NOx = 0.51 g/mi (chassis dynamometer) Engine (Hybrid-electric Bus) NOx = 0.17 g/bhp-hr (engine certification level) Baseline Diesel Bus NOx = 0.95 g/mi (chassis dynamometer) Engine (Baseline Diesel Bus) NOx = 0.19 g/bhp-hr (engine certification level) EF (Emission Factor) = Vehicle NOx (g/mi) Engine NOx (g/bhp-hr EFhybrid = 0.51 g/mi = 3.0 bhp-hr/mi 0.17 g/bhp-hr EFbaseline =0.95 g/mi = 5.0 bhp-hr/mi 0.19 g/bhp-hr

EFR (Emission Factor Ratio) =EFhybrid EFbaseline EFR =3.0 bhp-hr/mi =0.60 5.0 bhp-hr/mi Hybrid-Electric NOx cert = EFR * Engine NOx Hybrid-Electric NOxcert = 0.60*0.17g/bhp-hr =0.1 0 g/bhp-hr

### < 0.2 g/bhp-hr certification standard \ ManufacturerXYZ's hybrid bus would pass the supplemental check. Example 2

- For example, manufacturerABC produces heavy-duty hybridelectric buses and performs chassis dynamometertesting with the following data: Hybrid-electric Bus NOx = 1.53 g/mi (chassis dynamometer) Engine (Hybrid-electric Bus) NOx = 0.17 g/bhp-hr (engine certification level) Baseline Diesel Bus NOx = 0.95 g/mi (chassis dynamometer) Engine (Baseline Diesel Bus) NOx = 0.19 g/bhp-hr (engine certification level) EF (Emission Factor) =Vehicle NOx (g/mi) Engine NOx (g/bhp-hr EFhybrid = 1.53 g/mi = 9.0 bhp-hr/mi 0.17 g/bhp-hrMr. MatthewSpears December29, 2014 Attachment EFbaseline =0.95 g/mi = 5.0 bhp-hr/mi 0.19 g/bhp-hr



### EFR (Emission Factor Ratio) =EFhybrid EFbaseline 

### EFR =9.0 bhp-hr/mi =1.80 5.0 bhp-hr/mi Hybrid-Electric NOx cert = 

### EFR * Engine NOx Hybrid-Electric NOxcert = 1.80*0.17g/bhp-hr=0.31 g/bhp-hr

### > 0.2 g/bhp-hr certification standard ManufacturerABC's hybrid bus would not pass the supplemental check.



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