Matthew Rodriquez Secretaryfor EnvironmentalProtection
December 3, 2014
Matthew Spears Center Director 

# Air Resources Board Mary D. Nichols, Chairman

9480 TelstarAvenue, Suite 4 El Monte, California 91731 •www.arb.ca.gov

U.S. Environmental Protection Agency 2000 Traverwood Drive Ann Arbor, Michigan 48105
Dear Mr. Spears: Edmund G. BrownJr. Governor

Thankyou forthe opportunityto assistwith the development ofthe Phase 2 greenhouse gas regulations for heavy-dutyvehicles. Air Resources Board staff has prepared the enclosed assessment ofthe potential use ofcredits for solar reflective paint and solar control glazing forthese vehicle classes. To summarize, staff recommends that no credit be offered for solar reflective paint because such paintwould not result in significant benefits for heavy-dutyvehicles, and recommends a methodology to determine credits for solar control glazing.
Ifyou have any comments orquestions, please contact Ms. Kim Heroy-Rogalski, Manager, Strategic Planning and Development Section, at (916) 327-2200 or by email at kheroyro@arb.ca.gov. Sincerely,

Michael Carter, Chief Mobile Source Regulatory Development Branch
Enclosure

cc: JamesTamm, Chief Fuel Economy Division National HighwayTraffic SafetyAdministration 1200 NewJerseyAvenue, SE Washington, DC 20590
Kim Heroy-Rogalski, Manager Strategic Planning and Development Section 

### \

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 RecycledPaperExecutive Summary Solar Control: Heavy-Duty Vehicles
A White Paper
October 30, 2014

Solar reflective paint and solar control glazing can reduce the interiortemperature in a vehicle, thereby reducing the airconditioning requirements, and thus reducing fuel consumption. The Low Emission Vehicle Ill Regulations (LEVIII) include a greenhouse gas (GHG) creditforthis benefit, which is generally not reflected in emissions tests. The credit is based on the premise that the air conditioner can be downsized due to reduced energy demands. This paper presents a brief discussion ofthe potential use of such credits for heavy-dutyvehicles. Credits have been suggested bythe Enhanced Protective Glass Automotive Association (EPGAA)for solar control glazing to credit emission reductions for both the portion oftime these vehicles are driven and the portion oftime they are idled. Air Resources Board (ARB) staff believe a credit forthe brief idle time portion ofthe duty cycle is appropriate. This credit must be adjusted for a variety offactors such as insolation rate, daytime idling, and othertechnological factors. Staffdoes not believe it is appropriate to include a creditfor drive time. Staffalso does not believe credits for solar reflective paint are appropriate. Section I ofthis paper addresses the thermal control credits available in ARB's LEVIII regulation. Section II notes potential benefits from solar control paint and glazing. Finally, Section Ill provides suggestions and recommendations.


### I. Thermal Control Credits in Light-DutyVehicles In its LEV Ill regulations, ARB included credits forthermal comfort systems for \ passengercars as well as light dutytrucks (LOT) and medium duty passengervehicles (MDPV). These have been adopted bythe United States Environmental Protection Agency (EPA) as well. The passengercar credits are accrued through

**th~~use** ofsolar

/ control glazing (no more than 

### 2.9 gram per mile carbon dioxide (g/mi C02)), various ventilation approaches (credit of 1.0

- 2.1 g/mi C02 ), and solar reflective paint (0.4 g/mi C02 ). Similarthough slightly highercredits are available forthe other affected vehicles. A total thermal comfort credit of3.0 g/mi C02 is available for passenger cars, and 4.3 g/mi for LOTs and MDPVs. These thermal credits accountfor up to 2.1 percent of assumed GHG for advanced vehicles. The credits are based on the fact thatthe use of these approaches reduces the solar load while the vehicle is parked, which results in reduced cooling demand on the air conditioner, which enables the air conditionerto be downsized, thus reducing fuel use while driving. (Air conditioners forthe passenger market are sized to allowthe rapid cool-down ofa carthat has been parked in the sun,

1so a less hot internal temperature means less cooling needs be accomplished to achieve desired interiortemperatures.)
II. Solar Reflective Paint and Solar Control Glazing for Heavy-DutyTrucks A. Solar Reflective Paint Sunlightthat strikes a vehicle is composed ofa mix primarily ofvisible and infrared (heat) wavelengths. Solar reflective paints reflect the infrared portion ofthe solar spectrum, which contains about halfofthe total energy, while minimally affecting the visible light portion, so that perceived color remains unchanged. In 2008, the National Renewable Energy Laboratory (NREL) noted thatforsleeper cabs, solar reflective paint resulted in a greaterthermal benefit than for light-dutyvehicles dueto the greater proportion of paintto glass in the heavy-duty sector (Rugh, 2008). Lustbader (2014) concluded that electric air conditioner loads in sleeper cabs can be reduced by nearly 21 percentwith a switch from blackto white paint, corresponding to a 16.7 percent reduction in air conditioner battery capacity and a 48 pound weight reduction from the standard battery size. Lesser, though still significant reductions can be had while maintaining existing paint colors through the use ofpaints formulated to reflect the infrared ·wavelengths while maintaining the original visible color

.. There are no current efforts to use solar reflective paints in the heavy-duty market, although a relatively large percentage oftrucks are white, which typically reflect around 70 percent ofthe total solar spectrum. As a point of reference, most black paint reflects around 5 percent, while a color-matched solar reflective black paint might reflect 30 percent ofthe sun's energy, since the visible light must still be absorbed.


### B. Solar Control Glazing 

### \ When sunlight impacts the glazing ofa vehicle, some ofthe energy reflects offthe glazing, some is absorbed bythe glazing, and some penetrates through the

**~lazing.** The energythat ultimately makes it through the glazing, including that rera9iated from the absorbed portion, is called the total solartransmittance (known as TTS). That energy is then retained in the vehicle, much like occurs in a greenhouse. Currently, the windshields of most heavy-dutytrucks use solar absorbing glass. This glass absorbs

**~he** infrared heat energy. Ultimately, that heat energy is reradiated either into the cab or lostto the environment. The proportions depend primarily on the relative temperatures and wind flow.
The use ofoptimized solar control glazing for heavy-dutyvehicles was found to reduce the interiortemperature ofa parked truck by up to 5 degrees Celsius (Rugh, 2008). This reduction in the thermal load could make it feasible under certain conditions to shut down a truck that is being idled forcooling purposes.

2C. Potential Benefit ofSolar Reflective Paint and SolarControl Glazing Just as solar reflective paint and solarcontrol glazing can reduce cooling demand in passenger cars, they can also reduce cooling demand in heavy-dutytrucks. However, thermal comfort credits for heavy-duty vehicles need to be specificto the different characteristics ofthese vehicle classes. Heavydutyvehicles are operated in a different mannerthan passengervehicles, and in fact, each class of heavy-dutyvehicles may operate in a unique way. For example, class 8 line haul trucks may be legally driven up to 11 continuous hours in a 14 hourworkday before a ten hour rest break is mandated. Much ofthe driving mayoccurduring night-time hours when there is less congestion. Vocational trucks are more likelyoperated in urban situations, with many short stops throughoutthe work-day. These vehicles likelyoperate predominantly during daylight hours. Because the load from airconditioning is a small fraction ofthe available horsepower, use ofthe air conditioner has a minimal effect on fuel economywhile driving under most duty cycles. However, heavy dutyvehicles spend over 1,8001 hours peryear idling while the vehicles are being loaded or unloaded, while queuing, and during mandated rest breaks. Often, the engine is idled simplyto provide for drivercomfort. 2 Since up to a gallon offuel can be burned while idling per hour, rest period idling alone results in well over 800 million gallons peryear ofwasted fuel and associated emissions in the nationwide fleet. In some daytime situations, thermal comfort options such as solar control paint and glazing should enable the driverto shut offthe engine during short driving breaks (30 min or less), such as for loading and unloading, during moderate ambient daytime conditions withoutthe cab becoming uncomfortablywarm. However, longer breaks will result in uncomfortablywarm cabins during even moderately temperate days regardless ofthe thermal controls employed. 3 \ It is difficultto assess the potential emission reductions ifall heavy-dutytrucks used the
/,- highest level ofsolar control paint and glazing. This is dueto a numberoffactors. Solar control promotes thermal comfort while driving and during rest breaks and other engine idle times. To the extent that the load on the engine is reduced during driving operation bythe lowercooling demand and that load reduction corresponds to reduced emissions, there will be an emissions reduction benefit. However, the additional load on the engine from the airconditioner compressor in a large engine is less substantial than

1 This com-mon estimate ofidle time seems based on 6 hours idling perday, 300 days peryear. It appears consistent with thefindings from Lutsey et al's 2004 nationwide truck survey, who also noted thatwhile approximately 75 percent ofsurvey respondents idled to provide heating orcooling, 35 percent also indicated they idle to power -accessories, 13 percent idled to avoid start-up problems, and 9 percent idled merelyto drown out other noise. However, idling restrictions are becoming increasingly common. 2 Although anti-idling measures are in effect in California, vehicles meeting the clean idle standard are allowed to idle more than the 5 minutes otherwise allowed. Similar exemptions are in place nationwide for states that at least nominally prohibit idling. SeeATR12013. · 3 Consider howquicklythe interior ofa car parked in the sun will exceed 100 degrees Fahrenheit.

3the load on a small engine. Further, technology continues to be developed to lessen the impact on emissions from air conditioner use, especially in this sector. When parked, newertrucks can use battery-powered thermal comfort systems, auxiliary power units, or electric hoteling where available. However, during loading/unloading operations and queuing, the idling engine will likely be providing the powerforthermal comfort, and these technologies could result in emission reductions.
1. Benefits ofSolar Reflective Paint The potential emission benefitfrom a switch to solar reflective paint is difficultto quantify. First, one must accountforthe baseline color mix, which is biased towards white vehicles. Second, one must accountforthe fact that color-matched solar reflective paints remain much less reflective than white paint, as they must still absorb the visible light rays needed to produce the desired color. Third, solar reflective paints offer little or no benefitwhile the vehicle is in motion, since any heat buildup is lost external to the vehicle. Lustbader's reduction in the size ofan electric system remains real, but the fuel economy benefitwould seem to be derived from the small reduction in the needed battery packweight, and even this is only achieved ifthe units are sized specificto the colorofthe vehicle. A black solar reflective chassis would still need substantially morl3 cooling capacitythan awhite chassis, and unless manufacturers size the unitto the color ofthe chassis, both colors will end up with the larger unit.
2. Benefits ofSolar Control Glazing According to EPGAA, most medium- and heavy-dutytrucks are delivered with windshields having a TTS ofaround 58 percent. These windshields are frequently replaced; replacementwindshields are typically also solarabsorbing, but usually allow slightly more solar energy into the cab, with a TTS ofaround 62 percent, similar

**t~** that ofautomobile windshields. Solarcontrol glazing is commercially available that transmits far less solarenergy into the vehicle. A TTS somewhat above 40 percent is currently achievable, while still maintaining the 70 percent visible lighttransmittance that is required forvision glazing. Such glazing typically reflects most ofthe



### infra~ed rays (solar reflective4), and can be ceramic- or metal-based. NREL's testing ofa class 6 truck showed solar reflective glazing can reduce the interiortemperatures after a hot soak by 4.7 C, resulting in a 0.2 mile per gallon(mpg) increase over a baseline of 11.3 mpg on the SC03 cycle, but no change in fuel economy overa constant 65 mph cycle. Again, the primary benefit is obtained when a vehicle is parked (offor idling).
Gaines et al (2006) used the 2002 Vehicle Inventory and Use Survey data and other assumptions to estimate truckfleet idling, which has two components- rest period

4 The infrared rays, notthe visible light rays, are reflected. The glazing does not have a mirrorfinish. Itvisually appears much like non-solar reflective glazing.

4idling and workday idling.5 The analysis concluded that nearly 700 million gallons of fuel were used for rest period idling for long-haul sleepertrucks and another2.5 billion gallons offuel were used forworkday idling forvarious classes of heavy-dutytrucks. Whatfraction ofthe associated idle time would potentially be reduced by solarcontrol measures? In otherwords, what portion oftotal idle time occurs in increments of30 minutes or less during the dayduring times ofthe yearwhen ambient temperatures would allow engines to be shut down without interiortemperatures becoming excessivelywarm? There appearto be no strong data to answerthese questions, so a numberofassumptions will need to be made. These assumptions should be refined as data are obtained:

• Thermal comfort measures will not reduce rest period idling time oremissions (with a caveat about potential weight savings for electric systems) because even the best thermal control systems are insufficient overthe long term, and because rest-period options to idling already exist.
• ARB has some limited dataforClass 5-7 truck idling, showing thatthese vehicles tended to idle about 50 percent ofthe time thattheywere running each day.6 Linehaul trucks are reported to idle around 6 hours perday, be offforfour hours perday, and therefore be driven 14 hours perday on average. This implies that 30 percent ofthe time the truck is on, it is idling.
• ARB assumes that 25 percent ofworkday idling is queuing. While thermal controls may increase driver comfort during these periods, the engine generally remains on while in creep mode so thatthe truck can move with the queue. · • ARB assumes that 75 percent ofworkday idling is loading/unloading and short breaks (such as for meals). This is the potentially affected portion oftotal idle time. • Temperatures during winter and summer are too extreme to allowthermal comfort without some technology such as idling, heaters, orelectric air conditioners. • Temperatures during spring and fall are sometimes suitable to allowthermal cqmfort approaches to eliminate the need for idling during short stops (maximum of 

### 150 driving days/year). Early mornings throughoutthe summer may be sufficiently cool to avoida need for comfort idling during short stops, butthe insolation rate/angle is low during these times, so solar controls will be of minimal benefit. • Stops ofgreaterthan 30 minutes will require heating orcooling for drivercomfort even during moderate ambient conditions. (Note how quickly a parked carwarms,

5 Note thatthis figure is based on the 2002 Vehicle Inventory and Use Survey. Diesel fuel was substantially less expensive in that time period, on the order of$1.30 pergallon. It is possible that attoday's diesel fuel prices, discretionary idling may have been substantially reduced. However, ARB is aware ofno evidence to support such a supposition. 6 As part ofan NREL project being completed forARB, a numberoftrucks were datalogged. Draft data for 46 beverage deliverytrucks (class 7 day cabs) from operations in Fresno, San Diego, Buena Park and Hayward, totaling approximately 810 total vehicle days ofoperation, showed that 63 percent of logged time was spent idling. 53 percent ofthe time was spent idling by 31 linen deliveryvehicles (class 6 step vans) operating in Sacramento, Pittsburg, Hayward, Novato, San Jose, Concord, Paramount, Riverside, Santa Ana and Sylmarforabout 575 total vehicle days ofoperation, and 40 parcel deliveryvehicles (class 5-6 step vans) operating in Aliso Viejo, Costa Mesa and Sun Valley over about 690 total vehicle days ofoperation were idled about 44 percent ofthe time.

5even in the fall or spring.) ARB assumes that 50 percent ofstops are 30 minutes or more. • Seventyfive (75) percent of respondents in a survey performed by researchers at the University ofCalifornia, Davis, noted thatthey idled forthermal comfort. Thirty five (35) percent noted they idle to power accessories. Idling also occurs for other reasons in lesser percentages. Therefore, at most 65 percent of idling is solelyfor thermal comfort (Lutsey et al, 2004). ARB assumes idling for heating and cooling is evenly split nationalll, and that only idling for cooling is applicable here. In fact, the solarcontrol glazing could increase the heating needs in the early mornings and throughoutwinteras more ofthe warming solar rays are excluded.
• Since EPGAA reports truck glass is replaced as frequently as every six months, ARB assumes vision glazing has a TTS of62 percent. Alternately, a discounted credit forthe originally improved glazing could be incorporated.

All ofthese factors must be considered for an idle creditfor solarcontrol glazing. Using these assumptions, 50 percent (ofthe time vehicles are idled)* 50 percent (ofthe year when conditions are moderate)* 75 percent (ofthe idling time that is for loading, unloading/meals)* 50 percent (ofthese stops are <30 minutes)* 65 percent (ofthe time the idling is forthermal comfort)* 50 percent (ofthe thermal comfortthat is cooling) gives an applicable idling factor of

### 3 percent ofthe current engine operation time that could be reduced bythermal comfort's contribution to potential idle reduction. (In addition, not all idling occurs during the day, so the day/night correction factor discussed below must also be applied.)
Ill. Proposals, Adjustments, and Recommendations
A. Solar Reflective Paint Solar reflective paint has little or no benefitwhen a vehicle is in motion. However) if a credit for solar reflective paint is incorporated in the Phase 2 standards, ARB recommends adjusting the credit allowed in the light-duty rule (0.5 g/mi for light-duty trucks and medium-duty passengervehicles) by a baseline paint color adjustmentto reflect current estimates ofthe color mix (An estimated 30 percent ofClass 7 and 8 trucks are otherthan white or cream. 8) as well as applicable factors discussed above and the percent ofthe idle time that occurs during sunlight hours, discussed in the glazing section below. Because the expected COz benefits ofsolar reflective paint on heavy-dutyvehicles are expected to be insignificant compared to overall vehicle

7 California's Emission FACtors (EMFAC2011) model assumes California summer (cooling) months are March through September and winter (heating) months are Octoberthrough February, for a58/42 percent split. respectively. 8 Staffs nonscientific survey completed in 2009 in the Los Angeles area found that approximately 70 percent ofclass 7 and 8 trucks operating on the freeways during rush hourare white. The non-white trucks were often part ofa fleet, such as UPS, which specifies a particular paint color.

6emissions,9 ARB recommends that no credit for such paint be included in the Phase 2 GHG regulation.
B. Solar Control Glazing
1. EPGAA Proposal for Driving and Idling Credits Two credits were proposed by EPGAAfor solar reflective glazing. First, they suggest a credit to applyto the driving portion ofthe duty cycle, using the same formula as forthe LOT segment, with units adjusted as appropriate forthe heavy-dutyfleet. Second, EPGAA suggests a separate idling credit. This would be afunction of idle time, geographic location, TTS, and glazing area. Itwould use the base formula from the driving calculation which includes TTS and glazing area, possiblywith an increased Zvalue10 of0.55 (vs. 0.4 for LOT), butwith an adjustmentfor insolation rates (Much ofthe solar benefits work is completed at NREL's Golden, Colorado facility which may not have insolation rates typical ofthe national average.) and a multiplicand 1 0 , the fraction ofthe fleet that daytime idles, which they assumed equal to 0.7. It was acknowledged that this term needs refinement.
2. Recommendations for Driving Credits EPGAA's recommendations were based on the light-duty vehicle thermal comfort credits included in LEVI!I. The gram per mile credits were extrapolated based on the amount ofdownsizing thatwould be made to an airconditioner due to reduced solar load while a vehicle wasparked. Since emission tests obviously do not measure tailpipe emissions for cars that are not running, the benefit was manipulated into aform suitable to be applied as a credit to the driving cycle. Forthe LDV sector, air conditioner
use results in a significant load on the engine, substantially reducing fuel economy. However, as the engine gets more powerful, the impact ofthis additional load beComes smaller, and a lesser effect is seen on fuel economy. Thus, the potential benefitto downsizing is reduced in engines ofthe sizes used in the heavy-dutyfleet. In addition, the thermal benefitto solar control paint orglazing tends to be less substantial when driving, where more ofthe heat energywill desorb to the outside than to the inside due to airflow. Therefore, ARB believes that it is not appropriate to include a separate driving credit for solar control glazing in the Phase 2 GHG regulations.

9 0.5 g/mi * 0.3

### =0.15 g/mile credit, ignoring all factors needed to limit benefits calculations to short-term daytime idling. ARB staff believe this is negligible (less than 0.01%) compared to the Phase 1standard, which

. translates to 2016 g/mi C02• 10The Z-value represents the relationship between glazing performance and interiortemperatures ofa parked vehicle.

73. Recommendations for Idling Credits ARB believes a credit relating to the time the engine would have been idling to provide thermal comfort, but instead can be shut down, is appropriate. Note that dueto the limited applicabilitytimes, as discussed above, this credit will be small. Any credits must be crafted to ensure that manufacturers are nottaking credit for existing actions. For example, EPGAA proposed a baseline TTS for glazing of62 percent, based on the TTS oftypical replacement glass. However, EPGAA also noted that the glazing installed by manufacturers is often closerto 58 or59 percent TTS. Ifa credit were to be granted based on the higher replacement TTS, the manufacturers would receive a de facto credit. An overly generous credit could actually result in an overall emissions disbenefit; hence, EPA needs to ensure thatthe credits result in further reductions than those required by the emission standards, ratherthan in lieu ofother reductions.
The fo.rmula that EPGAA has suggested for idling credit is based on the light-duty credit calculation. A numberofadjustments must be made to the formula to reflect the heavydutyfleet application.

• Solar insolation rate: EPGAA suggested including an adjustmentfactorto account forthe fact thatthe published benefits were assessed at one geographic location, Golden, Colorado, which does not reflect the average solar insolation rate in the country. This is fine, although ARB staff believes this adjustment would be insignificantly small compared to other needed adjustments.
• Daytime idling percentage (lo): As EPGAA. mentions, the formula must be adjusted to compensate forthe portion of idling time that occurs during daytime hours, preferablythe hours when the solar radiation is substantial. Unfortunately, these data do not seem to be readily available. EPA offered some educated guess/anecdotal-based estimates as a starting point. Assuming that truckload carriers might drive .significant hours at night to avoid traffic congestion, EPA \ suggested a 50/50 split between daytime and nighttime idling. Forthe less-thantruckload and vocational freight, there is potentially more loading and unloading time, presumably during business hours, but likely less hoteling. EPA suggested a 70/30 split forthis category. Forvocational vehicles, EPA has idling weighting factors by speed bin. EPA suggests an 80/20 split, with most idling occurring during daytime hours. ARB does not have these data in-house; however, ARB does have some limited data on Class 5-7 trucks previously discussed, which suggests that these vocational truck types idle about 50 percent ofthe time, presumably during "normal working hours". A Texas study (AACOG, 2011) suggested that trucks stopped at rest areas are most likelyto be idling at night, which might be contrary to the presumption of night-time driving forthe truckload carriers.
• Thermal comfort adjustment: As previously discussed, thermal benefits would only accrue when the otherwise-idling engine is shut off. This could happen during periods when it is only being idled to provide cooling, the ambient conditions are moderate, and the idling period is short. Long idle times will still result in an

8- ----------

**-~~-** -- ----------'

excessivelywarm cab regardless ofthe efficacy ofsolar control glazing. This one adjustment would likely significantly reduce the size ofany available credit. • Future impactfrom increased hoteling electrification and othertechnologies: Truck stop electrification is increasingly available. This technology allows the truckto hook into the power grid forthermal comfort and accessories. The engine is then shut down. Other methodsto reduce engine idling forthermal comfort include batterypowered systems, and thermal energy storage systems. To the extentthatthese idling alternatives are utilized, the benefit ofsolar control paint and glazing to reduce idling use is minimized. Use ofthese approaches simultaneous with idle credits would result in inappropriate credit use. With the current nationwide trend in idling restrictions, the trend in idling time oughtto be in a significant decline. Nonetheless, approaches such as solar control glazing and solar reflective paintwill allow a battery-powered system to be downsized, thus somewhat reducing its weight and power needs. Othertypes ofthermal energy storage systems could also be downsized, with similar benefits. The electricity draw at an electrified truck stop would also be slightly reduced, reducing grid energy demand and possibly, peak energy usage.

Thus, while the proposed Z value of0.5 suggested by EPGAA seems reasonable, additional adjustmentfactors are required. The lo term proposed by EPGAA appears to only address the portion ofthe time that idling occurs duringthe day, which oughtto be specific to truck class. Since staff believes thatthe benefitwould only accrue during the dayduring those periods ofthe yearwith moderate ambient conditions, and for stops of 30 minutes or less, and utilizing the assumptions included in Section II.C, corrected as appropriate, a more detailed correction factor should be applied to 1 0 beyond the percent of idle time that occurs during the day. The correction factor should include the percent ofthe yearwhen conditions are moderate (50 percent), the percent ofthe idling time that is for loading, unloading/meals (75 percent), corrected forthe portion ofthese stops that are 30 minutes or less (50 percent), and the percent ofthe time thatthe vehicle is idling forthermal comfort, since idling for other purposes would presumably not be affected (65 percent), corrected forthe portion ofthe thermal comfort idling that is for cooling (50 percent). This gives an overall correction factor ofaround 6 percent of the current engine operation time that could be reduced bythermal comfort's contribution to potential idle reduction. The calculation, shown below, would also need to be converted into the metric used forthe Phase 2 GHG standards.

'[,.X G· [ n 

# l

Credit= Z

## x

# 6

1 G 1 

## x 1 0 

## xL 

## x0.0611

11Zis afraction representing the relationship between glazing performance and interiortemperatures ofa parked vehicle. T; is the thermal performance ofthe T' piece ofglazing. G; is the area ofthat piece ofglazing, while Gis

9It is also important that the credit include in some way a mechanism to ensure that replacement glazing maintains at leastthe same level of solar control as that assumed in the credit calculation for manufacturers utilizing the credit. If not, actual idle time reductions will last only as long as the original glazing.
IV. Conclusions and Overall Recommendations In sum, ARB supports an idling reduction credit based on the use ofsolar control glazing but believes the approach must be refined beyond that proposed by EPGAA to incorporate better idling data. Further, the credit should be based on the reduced fuel consumption resulting from a reduction in idle time, not on potential benefits from air conditioner downsizing as was the LEV credit. ARB does not support an additional separate credit for solar control paint and glazing that would applyto the driving portion ofthe duty cycle. It is importantto reiterate that while it might appearthatthe LEV credit is a driving credit, it was determined based on the ability ofthese controls to reduce the interiortemperature of parked cars, thereby allowing manufacturers to downsize the air conditionerwhile still cooling the car in a suitable time period. Therefore, the LEV credits are actually parked car credits manipulated into a per/mile metric.
ARB suggests the following formula, adjusted into the appropriate metricforthe Phase 2 GHG standards and adjusted for anyimprovements in staffassumptions, be used to determine credits for solar control glazing for heavy-dutytrucks, in conjunction with a requirement that replacement glazing be ofsimilar solar control levels as the glazing upon which the creditwas calculated. 

### \

# Credit~[zxt,T,~G'] xl0 

### xL x0.06

References: AACOG, Alamo Area Council ofGovernments. Heavy-Duty Vehicle Idle Activity and Emissions, San Antonio-New Braunfels MSA. 2011. ATRI, American Transportation Research Institute Compendium of Idling Regulations. Nov 2013.

the total glazing area in thevehicle. 1 0 is the percent oftimethat idling occurs duringthe day, and Listhesolar insolation rate adjustment factor discussed previously.

10Gaines, L., Vyas, A., Anderson, J., "Estimation of Fuel Use by Idling Commercial Trucks," 85th Annual Meeting ofthe Transportation Research Board, Washington, D.C., January22-26, 2006, Paper No. 06-2567. Lustbader, J, C Kreutzer, MAJeffers et al. Impact of paint color on rest period climate control loads in long-haul trucks. SAE Technical Paper 2014-01-0680. Lustbader, J, T Venson, S Adelman et al. Application ofsleeper cab thermal managementtechnologies to reduce idle climate control loads in long-haul trucks. SAE Technical Paper2012-01-2052. Lutsey, N, C Brodrick, D Sperling, and C Oglesby. Heavy-DutyTruck Idling Characteristics: Results from a Nationwide Truck Survey. Transportation Research Record: Journal ofthe Transportation Research Board, No. 1880, TRB, National Research Council, Washington DC pp 29-38. 2004. Rugh, J, R Farrington. Vehicle Ancillary Load Reduction Project Close-Out Report. Technology Report NREL/TP-540-42454. January2008
US DOE. Energy Efficiency and Renewable Energy. Vehicle Systems Simulation and Testing. DOE/EE-1023. pp 254-260. 2013.
Total solartransmittance test methodology: ISO 13877:2008 "Safety glazing materialsMethod for determination ofsolartransmittance"



### \

11