5
Vehicle Technologies for Reducing Load-Specific Fuel Consumption

The technologies that can be used to reduce fuel consumption in medium- and heavy-duty vehicles vary by vehicle type, duty cycle, and the year the technology becomes available. For instance, a Class 8 tractor trailer operating on the interstate will benefit from technologies that improve aerodynamic performance and reduce rolling resistance, whereas a Class 2b pickup truck will benefit little from these technologies. This chapter first reviews the ways in which energy is lost in the operation of medium- and heavy-duty vehicles. It then reviews technologies and techniques for reducing the fuel consumption of these vehicles, including technologies that improve aerodynamic performance and that reduce rolling resistance, auxiliary loads, and idle. It also covers mass and weight reduction, and intelligent vehicle technologies.

VEHICLE ENERGY BALANCES

The potential efficiency improvements being considered in this study can be illustrated by reviewing the energy losses for the various vehicle classes. The U.S. Department of Energy (DOE) 21st Century Truck Partnership Technology Roadmap (DOE, 2006) provides the following tables for energy losses. The engine losses were calculated from a typical accounting of fuel energy usage, such as that shown in Figure 5-1. The engine losses are primarily a result of heat transfer to the coolant and heat loss through the exhaust. The remaining energy is used to power the vehicle and auxiliaries under the conditions set forth in the tables below. In Figure 5-1, engine accessories are components essential to engine operation, such as the fuel pump, water

FIGURE 5-1 Energy balance of a fully loaded Class 8 tractor-trailer on a level road at 65 mph, representing the losses shown in Table 5-1. SOURCE: TIAX (2009).

FIGURE 5-1 Energy balance of a fully loaded Class 8 tractor-trailer on a level road at 65 mph, representing the losses shown in Table 5-1. SOURCE: TIAX (2009).



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5 Vehicle Technologies for Reducing Load-Specific Fuel Consumption VEHICLE ENERGY BALANCES The technologies that can be used to reduce fuel consump- tion in medium- and heavy-duty vehicles vary by vehicle The potential efficiency improvements being considered type, duty cycle, and the year the technology becomes avail- in this study can be illustrated by reviewing the energy able. For instance, a Class 8 tractor trailer operating on the losses for the various vehicle classes. The U.S. Department interstate will benefit from technologies that improve aerody- of Energy (DOE) 21st Century Truck Partnership Technol- namic performance and reduce rolling resistance, whereas a ogy Roadmap (DOE, 2006) provides the following tables Class 2b pickup truck will benefit little from these technolo- for energy losses. The engine losses were calculated from a gies. This chapter first reviews the ways in which energy is typical accounting of fuel energy usage, such as that shown lost in the operation of medium- and heavy-duty vehicles. It in Figure 5-1. The engine losses are primarily a result of then reviews technologies and techniques for reducing the heat transfer to the coolant and heat loss through the ex- fuel consumption of these vehicles, including technologies haust. The remaining energy is used to power the vehicle that improve aerodynamic performance and that reduce roll- and auxiliaries under the conditions set forth in the tables ing resistance, auxiliary loads, and idle. It also covers mass below. In Figure 5-1, engine accessories are components and weight reduction, and intelligent vehicle technologies. essential to engine operation, such as the fuel pump, water FIGURE 5-1 Energy balance of a fully loaded Class 8 tractor-trailer on a level road at 65 mph, representing the losses shown in Table 5-1. Figure 5-1 Energy balance of a fully loaded...losses shown.eps SOURCE: TIAX (2009). bitmap 

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES TABLE 5-1 Energy Balance for a Fully Loaded Class pump, and oil pump, while auxiliary loads are accessories used in a vehicle’s operation, such as the power steering, air 8 Vehicle Operating on a Level Road at 65 mph for One compressor, cooling fan, and air-conditioning compressor. Hour The energy losses for a Class 8 tractor with a 53-ft van Energy Sources Baseline (kWh) Baseline (hph) trailer, fully loaded to 80,000 lb gross vehicle weight (GVW) Engine losses per hour 240 321.8 and operating on a level road at 65 mph, for one hour, are Auxiliary loads 15 20.1 shown in Table 5-1. The energy losses for a Class 3 to 6 Drivetrain energy 9 12.1 medium duty truck, loaded to 26,000 lb GVW and operating Aerodynamic energy 85 114.0 on a level road at 40 mph for 1 hour, are shown in Table 5-2. Rolling resistance energy 51 68.4 (Note that this steady-state operating point is not typical of Total energy used per hour 400 536.4 the duty cycle for a Class 3 to 6 medium-duty truck.) The NOTE: hph, horsepower-hour. energy losses for a 40-ft transit bus with one-half seated SOURCE: TIAX (2009), p. 2-3. load (32,000 lb) and the air conditioning on, operating over the central business district cycle, for 1 hour, are shown in Table 5-3. Note the high percentage of energy devoted to TABLE 5-2 Energy Balance for a Fully Loaded Class 3 auxiliary loads. to 6 Medium-Duty Truck (26,000 lb) Operating on a Level Vehicle energy balances such as those described in Tables Road at 40 mph for One Hour 5-1 through 5-3 identify the energy required to propel a ve- hicle down the road at a specific speed and with a specific Energy Sources Baseline (kWh) Baseline (hph) load. The following sections break down these areas of losses Engine losses per hour 73.1 98.0 as follows: aerodynamics, auxiliary loads, rolling resistance, Auxiliary loads 1.5 2.0 vehicle mass (weight), and idle reduction. Drivetrain energy 3.3 4.4 Aerodynamic energy 18.9 25.3 Rolling Resistance energy 23.0 30.8 AERODYNAMICS Total energy used per hour 119.8 160.6 NOTE: hph, horsepower-hour. Truck Aerodynamics SOURCE: TIAX (2009), p. 2-5. Anyone comparing the commanding size of a tractor-van trailer combination to a small sedan or even a full-size sport utility vehicle (SUV) understands that the aerodynamic drag1 TABLE 5-3 Energy Balance for a 40-ft Transit Bus of these large vehicles exceeds that of any light-duty vehicle. Operating over the Central Business District Cycle for One Some quantitative comparisons of those differences will be Hour made later. For now, consider again the energy summary for the tractor-van trailer given in Table 5-1 and Table 5-4. Energy Sources Baseline (kWh) Baseline (hph) Clearly, for this class of truck, aerodynamic load reduction Engine losses per hour 86.8 116.4 is a key for successful fuel consumption reduction. Auxiliary loads 36.4 48.8 Drivetrain energy 13.4 18.0 Aerodynamic energy 1.3 1.7 Early Studies Rolling resistance energy 7.2 9.7 Total energy used per hour 145.1 194.6 K.R. Cooper of the Canadian National Research Council NOTE: Transit bus with one-half seated load (32,000 lb) and air condition - summarized some of the earliest heavy truck wind tunnel ing on. [Baseline] hph, horsepower-hour. testing performed in 1953 at the University of Maryland SOURCE: TIAX (2009), p. 2-6. (Cooper, 2004). Many of the aerodynamic design solutions now available or being developed for Class 8 tractors and box van trailers were evaluated in that 1953 study. Those devices were shown to reduce aerodynamic drag by about 50 percent TABLE 5-4 Operational Losses from Class 8 Tractor with as compared to the predominant truck configurations of the Sleeper Cab-Van Trailer at 65 mph and GVW of 80,000 lb 1950s (the cab-over-engine tractor). The “near-practical” Operating Load Power Consumed (hp) Power Consumed (%) streamlined result is shown in Figure 5-2. Airshield introduced a commercial cab roof-top air de- Aerodynamic 114 53 Rolling resistance 68 32 flector in about 1965. This device received some trucking Auxiliaries 20 9 company interest, especially after the 1973 petroleum crisis. Drivetrain 12 6 Braking 0 0 Total 214 100 1Aerodynamic drag refers to forces that oppose the motion of a vehicle through air. SOURCE: DOE (2008).

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 VEHICLE TECHNOLOGIES FOR REDUCING LOAD-SPECIFIC FUEL CONSUMPTION FIGURE 5-2 University of Maryland, streamlined tractor, closed gap, three-quarter trailer skirt, full boat tail. SOURCE: Cooper (2004), p. 15, Fig. 4, Case 8. Reprinted with kind permission of Springer Science and Business Media. Figure 5-2 University of Maryland streamlined tractor...fu.eps bitmap Industry interest was encouraged by the graphic illustrations air filters mounted under the hood. These changes resulted produced by the National Research Council of Canada, as in a significant reduction in aerodynamic drag compared to shown in Figure 5-3. contemporary tractor models. Continuing development led to additional improvements such as cab extenders to reduce the gap between tractor and Recent History trailer, more aerodynamic mirrors, and full-length side fair- The introduction of the Kenworth T-600 in 1985 marked ings. By 1990 all major truck/tractor manufacturers had in- the industry’s first serious attempt to incorporate aerody- troduced aerodynamic models, although “traditional” models namic improvements in truck tractors (see Figure 5-4). The continue to be available. See Figure 5-5 for identification of T-600 included features such as a streamlined hood and fend- the common aerodynamic features. ers, an aerodynamic faired bumper, fuel tank fairings, and FIGURE 5-3 National Research Council of Canada: Smoke pictures, cab with deflector (right). SOURCE: Cooper (2004), p. 11, Fig. 2. Reprinted with kind permission of Springer5-3 Smoke pictures, cab with deflector.eps Figure Science and Business Media. 1 bitmap

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES FIGURE 5-4 Kenworth 1985 T600 aerodynamic tractor. SOURCE: Photo courtesy of Kenworth Truck Company. Figure 5-4 Kenworth 1985 T600 aerodynamic tractor.eps bitmap J1263. This standard allows estimation of both the Early Efforts Toward Engineering Measurements coefficient of aerodynamic drag, Cd, and the rolling The development of aerodynamic features led to a need resistance coefficient, Crr. SAE J1263 was intended for test procedures that could quantify the performance of primarily for passenger car applications, and the ac- these features. Most industry standards were developed curacy and repeatability of this procedure may be through a consensus process by the Society of Automotive inadequate for heavy duty vehicles. Engineers (SAE). Some of the widely used standards are as • Wind tunnel tests. Truck companies began performing follows: wind tunnel evaluations. Since a limited number of wind tunnels are available that can handle full-size • Coast-down tests on a track. By 1976 SAE issued a trucks, scale models were widely used. By 1981, SAE procedure to quantify and standardize this test, SAE had developed a recommended practice, SAE J1252, FIGURE 5-5 Aerodynamic sleeper tractor aerodynamic feature identification. Figure 5-5 Aerodynamic sleeper tractor aero feature identifi.eps bitmap

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 VEHICLE TECHNOLOGIES FOR REDUCING LOAD-SPECIFIC FUEL CONSUMPTION for wind tunnel tests. This procedure is the only ac- Drag coefficients for current aerodynamically designed curate method of determining wind-averaged drag, by tractors with smooth-sided van trailers (T-T) are about 0.6 accounting for the effects of side wind. See Chapter 2 to 0.65, which is higher than the values normally found in for a description of the SAE J1252 test procedure. light-duty vehicles. Most current automobile sedans achieve • Fuel consumption measurement with full-size trucks. a Cd of about 0.3 to 0.4, and the Cd of SUVs is typically 0.4 In 1986 the SAE and the Truck Maintenance Council to 0.5. The higher Cd values for tractor trailers is primarily (TMC) introduced the joint TMC/SAE Fuel Consump- due to the fact that they are essentially large boxes optimized tion Test Procedure—Type II, SAE J1321, which for the movement of freight. provides the in-service fuel consumption of one test Drag coefficient values are usually measured in wind tun- vehicle compared to a control truck. This test allows nel tests. The Cd of a vehicle directly facilitates the compu- for correction of parameters outside the control of the tation of aerodynamic energy loss. Further, the wind tunnel researchers performing the test, such as ambient condi- test can provide a relatively simple and precise method to evaluate the wind yaw2 effects on a vehicle’s Cd (Cooper, tions and wind. 2004). An accurate and repeatable process for establishing Cd values is essential for the successful application of whole- SmartWay Partnership of the U.S. Environmental truck computer modeling to evaluate fuel consumption ef- Protection Agency fectiveness of various drag-reducing devices. The U.S. Environmental Protection Agency’s (EPA) Each truck tractor manufacturer has developed in-house partnership with the truck industry to reduce emissions processes to validate the technical performance of their (especially greenhouse gases) and fuel consumption alike is aerodynamic solutions. Manufacturers do not publish Cd described in Chapter 3. The EPA’s SmartWay truck specifica- values, evidently because the procedures used by different tion has a significant dependence on improved aerodynamic manufacturers are not known to be directly comparable. performance. It requires certain fuel consumption reducing Manufacturers have not agreed to use a common standard aerodynamic design features to be applied on tractor-van such as SAE J-1252. trailer combinations (Figure 5-6): Aerodynamic Energy Loss • The SmartWay tractor must be a high-roof aerody- namic sleeper cab, with aerodynamic bumper, mirrors, As described in the Road Load Power paragraph in Chap- side truck fairings, side extender fairings, and roof ter 2, the resisting aerodynamic horsepower is proportional to Cd × A × V³, where A = frontal area and V = forward fairings. All six domestic tractor manufacturers now supply SmartWay compliant tractors. velocity. This illustrates the important role of vehicle speed • The SmartWay-certified van trailer must be equipped on aerodynamic horsepower loss. It is helpful to graphically with side skirt fairings plus either a trailer boat tail display aerodynamic power consumption as a function of road speed. Consider Figure 5-7, where the blue (Cd = 0.625) or a tractor-trailer gap fairing. The combined trailer aerodynamic treatment is estimated to achieve at least curve is typical of today’s tractor-trailer combination. The a 5 percent fuel consumption reduction compared to green curve represents a 20 percent reduction in the Cd, and a standard trailer. At least eight trailer manufacturers therefore in the aerodynamic power loss. A 20 percent reduc- supply SmartWay-compliant trailers (EPA, 2009). tion in Cd results in a fuel consumption reduction of about 10 percent at 65 mph (TMA, 2007, p. 10). As noted in Chapter 3, California adopted the SmartWay Figure 5-7 also shows the curve for power consumed by specification and validation processes as integral to its Global tire rolling resistance. As described in the Chapter 2 para- Warming Solutions Act in December 2008. That adoption graph on road load power, the tires’ rolling resistance power loss is proportional to: Crr × W × V, where W = vehicle gross provided for a mandatory introduction schedule of these weight and V = forward velocity. The Crr value used in the fuel-saving specifications for both tractors and trailers in the 2011-2013 period (CARB, 2008). figure is typical of those on current tractor trailers but not of the lower value required for SmartWay certification. Heavy-duty tractors not only have higher Cd values than Technology of Aerodynamic Improvements light-duty vehicles, they also have a frontal area that is 3 to The standard metric for comparing aerodynamic losses is 3.7 times larger than cars and SUVs. The large frontal area the drag coefficient, Cd (see in Chapter 2 the section “Truck is driven by the need to package a large payload capacity. Tractive Forces and Energy Inventory”). Vehicle designers As a result, the Cd*A values (drag coefficient times frontal seek to minimize the drag coefficient in order to reduce fuel area) of heavy trucks are roughly 4.7 to 7.7 times higher than consumption at higher vehicle speeds, where aerodynamic drag represents a substantial fraction of the energy needed 2 “Yaw”refers to a wind whose direction is not directly in line with the to keep the vehicle moving. forward motion of the vehicle (i.e., a side wind).

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES FIGURE 5-6 2009 model year Mack Pinnacle (left) and Freightliner Cascadia (right) SmartWay specification trucks. SOURCE: Courtesy of Mack and Freightliner Cascadia. 2009 model year Mack...SmartWay specification t.eps Figure 5-6 1 bitmap, 2 clipping paths light-duty vehicles, which results in an aerodynamic power the WAAS must be verifiable. For example, will a tractor- consumption 4.7 to 7.7 times higher. The benefits of aerody- container/trailer chassis operate at a low average mph by namic features are a strong function of both operating speed virtue of its operation over short distances between ports and annual vehicle miles traveled (VMT). As Figure 5-7 and rail terminals? CARB has taken this issue into account shows, aerodynamic drag is larger than rolling resistance in its greenhouse gas (GHG) regulation, where drayage trac- at speeds above 48 mph for a typical current truck. At 32 tors are exempt if operated within 100 miles of the port. If mph, however, aerodynamic drag is only half of tire rolling this approach is applied in the general case, it would likely resistance, and aerodynamic drag becomes insignificant at require use of electronic onboard data recorders to substanti- low speeds. The sensitivity to VMT applies to any fuel- ate the short distance and/or below-speed-hurdle reality. The saving feature: the more miles a vehicle travels, the larger required record keeping and oversight could become very the potential fuel savings becomes. burdensome. In determining whether to apply aerodynamic features to a vehicle, it may be appropriate to consider a duty cycle Details of Aerodynamic Solutions average road speed hurdle. A method to quantify a weighted aerodynamic-average speed (WAAS) has been established There are four regions of the tractor-van trailer combina- that provides for an average of the mileage-weighted veloc- tion truck that are amenable to aerodynamic design improve- ity3 (V³). If it is deemed that a speed hurdle is appropriate, a ments. These regions include the various tractor-related numerical value for the hurdle speed must be established, and details, the tractor-trailer gap, the trailer skirt, and the trailer FIGURE 5-7 Aerodynamic and tire power losses for tractor-van trailer combination. Figure 5-7 Aerodynamic and tire power losses for tractor-van.eps low-resolution bitmap--suggest redraw (can’t crop off surrounding rule, head, without losing bottom of ruled box)

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 VEHICLE TECHNOLOGIES FOR REDUCING LOAD-SPECIFIC FUEL CONSUMPTION FIGURE 5-8 Tractor-trailer combination truck showing aerodynamic losses and areas of energy-saving opportunities. Percent changes refer to fuel consumption. SOURCE: Based on ractor-trailer combination...energy-saving opp.eps Figure 5-8 TWood (2006). Courtesy of Richard Wood. bitmap “base” fairing, which are all illustrated in Figure 5-8, along Shorter-haul operators tend to avoid aerodynamic fairings with the approximate fuel consumption reductions that seem because they provide limited fuel savings and are prone to to be achievable in the near term. damage in urban operations and during frequent stops at loading docks. Day cab tractors often are equipped with only a roof fairing, and for nonvan applications they may carry no Aerodynamics of the Truck Tractor fairings at all. Day cab tractors make up about one-third of The contemporary image of aerodynamically optimized all tractor sales, and so they are a significant portion of the tractors is that of sleeper cab tractors equipped with many market. fairings, such as the SmartWay trucks shown in Figure 5-6 Most tractor manufacturers introduced tractor offerings and the left-side image shown in Figure 5-9. These tractors in the 2003 to 2008 period that included purposeful, major are typically used in long-haul applications where the ability improvements in their aerodynamic performance accom - to provide “hotel” accommodations is important. However, plished by attention to many details and utilizing most of the many long-haul operators use a terminal-to-terminal system evaluation tools noted earlier. Reports of fuel consumption that does not require sleeper tractors. These operators use day reductions of up to 6 percent were received during committee cab tractors such as that shown on the right in Figure 5-9. site visits. FIGURE 5-9 Volvo full sleeper cab (left) and day cab (right). SOURCE: Courtesy of Volvo. Figure 5-9 Volvo full sleepter cab and day cab.eps 1 bitmap

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES TABLE 5-5 Class 8 Tractor Aerodynamics Technologies, Considering the 2012 Time Frame Technology Fuel Consumption Reduction (%) Cd Improvement (%) Cost ($) Industry Adoption Rate (%) Day cab roof deflector 4-7 13 1,000-1,300 Most Sleeper roof fairing 7-10 15-20 500-1,000 Standard Chassis skirt 3-4 4-7 1,500-2,000 50-60 Cab extender 2-3 4-5 300-500 80-90 Next-generation package 3-4 6-8 2,750 2012 Introduction SOURCE: TIAX (2009), p. 4-35. Table 5-5 shows the market shares of various aerodynamic trailer is just temporary, but in some cases this fuel-wasting features on aerodynamic-style tractors. Roof shields have a combination may be long term. very high market share, while the relatively damage-prone Another marketplace factor in tractor design that delays chassis skirts have a lower share. The side-of-cab extender full implementation of aerodynamic features is the preference works with the roof shield to minimize the gap between trac- for traditional styling. This preference for a traditional look tors and trailers. This gap has a major role in determining is prevalent among owner-operators, and many small fleets the overall vehicle Cd. The recommended maximum gap3 is use traditional styling as a driver retention feature. Notice the typically 30 in. from the rearmost feature on the tractor to differences in traditional styling compared to aerodynamic the trailer face. Smaller gaps do have drawbacks, however, styling in Figure 5-10. Traditional features known to have in that they limit the ability of the vehicle to operate in tight high drag-inducing effects include the large, flat bumper, spaces. along with features protruding into the airstream such as head The next-generation aerodynamics package shown in lamps, air cleaners, and dual exhaust stacks, as well as “west Table 5-5 represents the forecast of tractor manufacturers for coast” side mirrors. While manufacturers have made useful sleeper cab tractor aerodynamics improvement in the 2012 aerodynamic improvements to traditional models of years time frame. These features will be designed and optimized gone by, these traditional features are believed to invoke a for long-haul applications. It is expected that many of these fuel consumption increase of at least 5 percent compared to features may not be compatible with short-haul operations, the aerodynamic model. (TIAX, 2009, Table 4-24). Some and thus their application on day cab tractors will be limited. operators are well aware of the fuel consumption penalty, Characteristics of short haul operation include curb encoun- while others are likely to underestimate it. ters, severe road-crossing humps, backing maneuvers, and Day cab tractors constitute roughly one-third of Class 8 tight street-side clearances. All of these combine to damage tractors. So far it has not been possible to match the aerody- many of the aerodynamic surfaces that could be successful namic performance of the best sleeper models with day cabs. in long-haul duty. Fortunately, it appears that many of the day cab and other There are two consequences of the fragility of tractor short-haul tractors accumulate fewer miles and thus consume aerodynamic features that must be considered. One is that less fuel than over-the-highway tractors. More specific data trucks specified with many aerodynamic features will not gathering is needed to quantify the fuel consumed by various be attractive or cost-effective in short-haul operations, be- applications of tractor trailers. cause of the fragility of aerodynamic features and because A 2-year collaborative study of a variety of design im- of restricted maneuverability. The other issue is that tractors provements that would reduce aerodynamic drag on tractor specified for short-haul operations will be less efficient if trailers was completed in 2007 by four members of the Truck they are pressed into long-haul service for any reason. Exces- Manufacturers Association (TMA) and DOE. Their research sive specialization of tractors can lead to logistics problems evaluated the effect of post-SmartWay designs on combina- for operators, as well as to lower used tractor values in cases tion tractor-trailer aerodynamics. A number of potential trac- where the original operating intent does not match the second tor features were evaluated, including alternative rearview buyer’s application. An example of this is sleeper cab tractors mirror designs, treatments of the tractor-trailer gap such as with full-height air deflectors pulling flat bed trailers. In this gap fillers and trailer gap flow control devices, and features case the aerodynamic feature actually costs fuel rather than to manage airflow under the vehicle and between the tractor saves fuel, because the high roof sleeper increases the frontal and trailer. In addition to the tractor features, a number of area of the truck beyond what the trailer requires. In many trailer features also were evaluated. cases the application of a high roof sleeper with a flat-bed The 2007 TMA/DOE study started with a computational fluid dynamics (CFD) modeling evaluation of potential aerodynamic feature concepts. The CFD models allowed the researchers to explore the effect of many design parameters 3 “Gap” refers to the distance from the rearmost vertical cab feature to on Cd (see in Chapter 2 the section “Computational Fluid the front of the trailer face; where a cab extender is employed, it is this Dynamics”). The most promising concepts from the analyti- rearmost feature.

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 VEHICLE TECHNOLOGIES FOR REDUCING LOAD-SPECIFIC FUEL CONSUMPTION FIGURE 5-10 Peterbilt Traditional Model 389 (left) and Aerodynamic Model 387 2 (right) (SmartWay). SOURCE: Courtesy of Peterbuilt Motors Company. Figure 5-10 Peterbilt Traditional Model 389 and Aerodynamic.eps cal study were then tested in either scale model or full-scalebitmap 1 engine size itself. For example, “light-hybrid” systems have wind tunnels to validate the modeling, quantify the Cd im- been mentioned as very useful to reduce light-load engine provements and further refine the concepts. Finally, full-scale operation in the tractor-trailer class. Unfortunately, a corre - prototype hardware was created for vehicle testing using the sponding reduction of engine size and heat rejection does not SAE J-1321 protocol (TMA, 2007, p. 5). seem likely, since peak power demand will still be fulfilled The 2007 TMA/DOE study successfully revealed im- only from the engine under many conditions. Similarly, most proved aerodynamic design features, but it also served to “bottoming-cycle” concepts will demand additional under- spotlight the difficulties of achieving major new reductions hood space and will greatly increase overall power train heat in tractor and tractor-trailer Cd. This last point also confirms rejection, as opposed to heat rejected in the exhaust gases, that today’s modern tractor designs already perform well further challenging frontal styling and possibly increasing aerodynamically, within constraints such as the need to Cd values. provide payload capacity and to be compatible with existing infrastructure such as loading docks. Aerodynamics of the Truck Trailer (with Focus on Typical The heat management requirements present another ve- 53-Ft-Length Box Vans) hicle design factor that influences the aerodynamic character- istics. Larger cooling packages limit the ability of designers Significant progress has been made with aerodynamic to reduce vehicle Cd. The total heat rejection from the vehicle components added to the trailer (see Table 5-6). Unfortu- determines the size of the cooling package required. The heat nately, there are three major impediments to widespread rejection includes engine-related heat rejection from the en- incorporation of aerodynamic trailer features. One is that gine radiator, charge air cooler, and exhaust gas recirculation in many operations the tractor and trailer owners are not (EGR) coolers, but there are other sources of heat rejection as the same. As a result, the trailer owner does not benefit well. The transmission and steering systems may have cool- from the fuel consumption reduction achieved by pulling an ers, along with the air-conditioner condenser. The addition aerodynamic trailer. The second issue is that there are many of charge air cooling in the early 1990s, and the addition of more trailers than tractors, since trailers are widely used as EGR in 2002, has led to increased cooling system size and temporary storage. As a result, the investment in aerody- heat rejection requirements. Certain engine efficiency design namic improvements must be amortized over many fewer features are mentioned in Chapter 4 that might reduce the miles than is the case for tractors. The third impediment is size of current truck cooling system components and/or basic the reality that there are no aerodynamic-system integrators TABLE 5-6 Current Van Trailer Aero-Component Performance Trailer Aerodynamic Technology Skirts Boat Tails Nose Cone Vortex Stabilizer Bogie Cover Range of fuel economy improvement (% mpg) 5.6-7.5 2.9-5.0 2.0->4.0 1.0 1.0 Range of costs $1,600-$2,400 n/a $800-$1,260 $500 n/a SOURCES: Based on responses to committee questionnaire and information on manufacturers’ websites.

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00 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES in the medium- and heavy-duty trucking industries. Trailer Pneumatic Blowing to Reduce Trailer Drag manufacturers are not owned by or related with tractor One researcher has extensively studied this concept, companies, and trailer aerodynamic-device manufacturers where low-pressurized air is discharged across curved trail- constitute yet a third layer of unaligned companies. For the ing surfaces used on the trailer’s rear face. Reported results most part it falls to the carriers themselves to sort through the indicate that a fuel consumption reduction of about 8 per- emerging aerodynamic devices to find the most cost effective cent at 65 mph may be achievable with this process. (The solutions. 8 percent is net savings, after accounting for the energy to Table 5-6 gives a partial summary of supplier-reported in- pressurize the required plenum, Englar, 2005, p. 12). Such formation obtained from responses to a committee question- a system would need to be integrated into the trailer design naire4 (see Figures 5-11 to 5-14). Data are typically reported for effective packaging, including compatibility with loading from SAE J1321 full-vehicle tests, in mpg improvement. docks. One trailer aerodynamics manufacturer, AT Dynam- However, individual testing procedures are not consistent, ics, has recently initiated development for a production- average test speeds differ, and it is not known whether the viable active flow control system for trailer rear edges. The statistical requirements of the test procedure are consistently cost and complexity of a pneumatic blowing system would adhered to. Also, the data are not adequate to conclude that be a substantial challenge to production implementation. benefits achieved by combining aerodynamic devices would be completely additive. In a section below, results from a Cost-Effectieness combination of devices are presented, and these results show DOE remarked in a December 4, 2008, research solicita- that simple addition of individual results does not provide tion that “there has not been a strong pull from fleets due to the correct result. concerns about cost, return on investment, durability and Note that the combined effects of several aerodynamic maintenance requirements.” Much of this lack of demand features (Full Package, in Figure 5-15) provide an average stems from the reality of trailer quantities. Currently, the fuel consumption reduction of 9.3 percent. The full pack- trailer-to-tractor ratio is about 2.8. Most larger trucking age includes the partial gap filler, full or partial trailer skirt, companies report individual ratios ranging from about 1.1 and base flaps (base fairings and boat tails). Further, if it is to 4.0. One large private carrier reported a trailer-to-tractor assumed that individual performances at the 75th percen- ratio exceeding 8 (Transport Topics, 2009). tile would eventually be achieved by 2015-2020, then the This reality adds to the difficulty of adding aerodynamic combined full package (of partial gap, full skirt, and base devices within normal and favorable capital acquisition met- flaps) would be 12.1 percent. This result is derived through rics, such as net present value (NPV). The NPV for trailer a method of multiplication of fuel consumptions reductions.5 skirts is strongly dependent on fuel prices and can easily Although there are more than 10 independent manufacturers exceed a 3-year zero-cost hurdle at a 2.8 trailer-to-tractor of trailer aerodynamic devices, at least eight trailer manufac- ratio. The retrofit of trailer aerodynamic devices might be turers have certified 53-ft van trailers in the EPA’s SmartWay a useful fuel-savings strategy, due to the long lifetime of Partnership (EPA, 2009). One trailer manufacturer, Wabash highway trailers, which is 20 years or more, as a result of National Corp., announced in July 2009 the production avail- their low on-road utilization (compared to tractors). ability of a trailer skirt of its design. Another cost-effectiveness issue is the fact that trailer aerodynamic improvements in duty cycles with low aver- age speeds must be judged as a particularly poor value. For example, the fuel consumption benefit decreases by nearly 4 Trailer Aerodynamic Component Performance. Private survey, NRC 90 percent if the average speed is 30 mph rather than 60 mph Committee on Medium and Heavy-Duty Vehicles, May to August, 2009. (see Figure 5-7). Respondents included AdamWorks, ATDynamics, Air Tab, Freight Wing, Inc., Laydon Composites Ltd., Nose Cone Manufacturing Co., Wabash National Corp., and Windyne, Inc. (remarks only). The committee also Safety Issues for Trailer Aerodynamic Devices obtained material from the websites (accessed August 2009) of manufac- turers that did not return the survey questionnaire, including Aerodynamic Since damage in normal vehicle operation is a major is- Trailer Systems (http://fuelsaverbyats.com/ats_company_info.htm), Nose sue with aerodynamic features, virtually all reporting skirt Cone Manufacturing Co.(http://www.nosecone.com/apvan.htm), Transtex developers have placed a high priority on ensuring that their C omposites (http://www.transtexcomposite.com/); and Windyne Inc. (http://www.windyne.com/). designs are significantly road damage tolerant. Many have 5The fuel consumption reduction of the combined technology packages video clips on their Web sites showing resistance to railroad is calculated multiplicatively (not additiely) according to the following grade crossing humps, steep loading dock accesses, and equation: snow accumulation or snow piles, as well as low-speed col- % FCPackage = 1 − (1 − % FCTech 1)(1 − % FCTech 2)(1 − % FCTech N) lisions with equipment such as fork-lift trucks. Nevertheless, where % FCTech x is the percent reduction of an individual technology, and caution is appropriate, as a proliferation of such low-hanging therefore (1 − % FCTech x) is the consumption associated with the reduction devices may create a new source of on-road hazards similar (personal communication between TIAX consultant Matt Kromer and C. to tire tread sections today. One manufacturer, AdamWorks, Salter).

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0 VEHICLE TECHNOLOGIES FOR REDUCING LOAD-SPECIFIC FUEL CONSUMPTION FIGURE 5-11 ATDynamics trailer tail (left) and FreightWing trailer skirt (right). SOURCE: Courtesy of Freight Wing. Figure 5-11 ATDynamics trailer tail and FreightWing trailer.eps 1 bitmap with 2 clipping paths FIGURE 5-12 Nose cone trailer “eyebrow.” SOURCE: Photo provided with permission by FitzGerald Corporation, national marketer for Nose Cone Mfg. Co. Nose Cone is a registered trademark. Figure 5-12 Nose cont trailer Eyebrow.eps bitmap FIGURE 5-13 Laydon vortex stabilizer (left) and nose fairing (right). SOURCE: Courtesy of Laydon Composites. Figure 5-13 Laydon vortex stabilizer and nose fairing.eps 1 bitmap

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0 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES TABLE 5-16 Summary of Impacts of Weight on Fuel Consumption of Trucks by Class Truck Class Weight Range Studies Reported Fuel Efficiency Impact Comments Source Combination 65-80k 0.5% per 1000 lb reduction 5.96 mpg at 65k NESCCAF/ICCT (2009) Class 8 5.4 mpg at 80k Highway drive cycle with some grade change Combination 20-80k 0.7-1.0% per 1000 lb level terrain Derived from monitored operation of Capps et al. (2008) Class 8 1.2-1.5% on upward grade route six similar trucks, combination of dual <0.1% on downward grade and single tire data Class 8 Not specified 0.4-1.0% fuel savings per 1000 lb weight EPA SmartWay reduction presentations and fact sheet Class 8 21-80k 2.0-2.4% per 1000 lb over hill climb and Single truck driven over routes of Strimer et al. (2005) rolling terrain different terrain at different weights 1.0% on level terrain 1.6% in stop/go Class 6 Not reported Fuel economy increase 2.4% per 1000 lb Model result, using CILCC drive NREL (2004) hybrid cycle; mostly city and suburb, favors hybridization Bus, 40 ft 35k baseline, ~2.0% fuel consumption reduction per Central business district cycle NREL (2002, 2004) conventional drivetrain 1000 lb 1.66 percent fuel economy gain per 10 Hybrid IFEU (2003) percent mass reduction Conventional bus 3.75-7.5 percent per 10 percent wt Urban operation. Wt effects less reduction inter-city Scheps, 2009a Class 2b ~8000-9000 lb 3-6% fuel economy improvement per 10% Adjusting rear axle ratio also done to weight reduction;b higher values cited in pickup or van give higher impact TIAX (2009) urban delivery, 7.5% per 10% wt reduced IFEU (2003) aRandall Scheps, Aluminum Association, “The Aluminum Advantage: Exploring Commercial Vehicles Applications,” presentation to the committee, Ann Arbor, Michigan, June 18, 2009. bLarger impact assumes engine is resized. other hybrid components add 300 to 1000 lb for trucks and tel loads in Class 8 long-haul tractor trailers. The assessment even more in bus applications. Hybrid components are de- of the technologies comes from the study TIAX conducted scribed elsewhere in Chapter 4. for the committee (TIAX, 2009). T ruck idle reduction technologies fall into five categories: Weight Reduction Summary TIAX in its report for the committee summarized weight • Automatic shut-down/start-up systems reduction fuel consumption reduction potential by ranges of • Battery-powered years and application, as shown in Table 5-18. • Fuel perated heaters • Auxiliary power units or generator sets • Truck stop electrification IDLE REDUCTION Idle reduction10 technologies use a portion of a vehicle’s Each idle reduction technology targets a specific set of op- engine output to power auxiliary systems, which are better erational requirements. Benefits will depend on the amount suited to the functions they are designed for. Idle reduction of idling, climate, time of year, and types of auxiliary loads. technologies that reduce in-use idling in traffic or at work There is not one solution that fits the northern (high heating sites using electrification of auxiliaries and engine off at loads) and southern (high cooling loads) climates. There is idle are discussed in the Diesel Engine and Hybrid Vehicle a great deal of information on idle reduction strategies, fuel paragraphs of this chapter. Creep devices are discussed in economy, and costs on EPA’s SmartWay Web site. the Transmission and Driveline Technology paragraph. This paragraph focuses on approaches to reduce the overnight ho- Automatic Shutdown/Startup Systems Automatic engine idle management systems monitor 10 “Idlereduction” in this report refers to technologies and practices that cabin and engine temperatures and turn the engine on/off as reduce the amount of time a vehicle idles the internal combustion engine.

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 VEHICLE TECHNOLOGIES FOR REDUCING LOAD-SPECIFIC FUEL CONSUMPTION TABLE 5-17 Summary of Weight-Reduction Estimates and Weight-Increase Offsets Truck Class Weight Reduction Potential Weight Increase Potential Comments Source Class 8 Wide singles with aluminum wheels afford up 300 lb, urea; Some of these changes already Michelin combination to 340 kg total weight savings over duals with 450 lb, APU; on trucks in 2007 trucks steel; 100 lb savings, aluminum fifth wheel + 60-80 lb, DPF; EGR cooler systems, 40 lb Rhein report 3000 lb weight savings said achievable by Ogburn et al. (2008) tag axle, engine downsize, wide single tires, lighter trailer Bottoming cycles and NESCAFF/ICCT (2009) other waste heat recovery, 240 lb and up Hybridization can eliminate transmission and Batteries offset weight mechanical pumps and alternator savings, 200-2000 lb Sullivan, 2007a 21st Century Truck Partnership agreed on goal of 20% weight reduction Recent Volvo press release says 20% reduced FleetOwner (2009) weight feasible in 10 years 25% weight reduction estimate by American Transport Topics (2009) Iron and Steel Institute Trailers for Latest trailers with new materials and Aerodynamic devices Lightweighting already under Etrucker.com, June 2006 Class 8 composite structures are ~1,000 lb lighter than for trailers weigh about way utility trailer press release; previous generation 50-200 lb Great Dane Class 3-6 Already in place except urea; not delivery much change 2007 and beyond Engine; Navistar reports its engine up to 800 Navistar does not use SCR for Navistar (2009) lb lighter than competitors’ engines 2010 Gibbs, 2009b Bus Use of lightweight materials and designs has Fisher Coachworks, used shown path to reduce bus weight by ~10,000 advanced stainless steel Wall et al. (2006) lb, an ~50 percent reduction Scheps, 2009c Use of aluminum demonstrated 3,000 lb China reduction Class 2b Similar to passenger cars See NAS reports on autos aR.Sullivan, “Parasitic Energy Loss Reduction,” presentation to the Committee on Review of the 21st Century Truck Partnership, Washington, D.C., February 8, 2007. bJ. Gibbs, Presentation to Calstart by the U.S. Department of Energy, Vehicle Technologies Program. March 2009. cRandall Scheps, Aluminum Association, “The Aluminum Advantage: Exploring Commercial Vehicles Applications,” presentation to the committee, Ann Arbor, Michigan, June 18, 2009. FIGURE 5-38 Weight reduction opportunities with aluminum. SOURCE: Randall Scheps, Aluminum Association, “The Aluminum Advantage: Exploring Commercial Vehicle Applications,” presentation Figure 5-38 Weight reduction oppor tunities with aluminum.eps to the committee, Ann Arbor, Mich., June 18, 2009. low-resolution bitmap--legibility is degraded

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES TABLE 5-18 Weight-Reduction-Related Fuel TABLE 5-19 Comparison of Automatic Shutdown/Startup Consumption Reduction Potential (percentage) by Class Systems 2013-2015 2015-2020 Cummins BBW ICON™ TAS Tractor trailer 0.8 1.25 Feature/Supplier IdleSmart Idle Control Temp-A-Start Class 6 box truck 2.0 4 Class 6 bucket truck 1.6 3.2 Monitors temperature inside ✓ ✓ ✓ Refuse truck — 1 and out Urban bus 3.0 6.25 Auto starts engine ✓ ✓ ✓ Motor coach 0.7 1.05 Increases engine speed for ✓ ✓ Class 2b pickup and van 0.4 0.75 maximum efficiency Monitors system (i.e., oil and ✓ ✓ ✓ cab temperatures, battery voltage) needed to maintain the desired temperatures. Several engine Heats and cools cab ✓ ✓ ✓ Idles down manufacturers offer electronically controlled optimized ✓ ✓ Shuts down engine ✓ ✓ ✓ idling control devices. Higher end integrated systems include Transferable to successive ✓ ✓ ✓ thermal storage. More advanced systems run the engine at trucks higher load to maximize engine efficiency when it is on. Weight (lb) 30 na 14 Table 5-19 characterizes several such systems. Duleep11 Retail price $3,750 $1,325 $2,500 estimates that these systems reduce fuel consumption by 3 SOURCE: TIAX (2009), p. 4-90. percent. Battery-Powered use significantly less fuel than the primary engine by sup- plying heat from either a combustion flame or a small heat Battery-powered idle reduction systems incorporate the exchanger, which is more energy efficient than using an use of either the vehicle’s battery or a separate battery pack engine cycle to achieve a heating affect. In model year (MY) to power the heating and/or cooling of the cab and powering 2007, there was about 10 percent market penetration for the of onboard appliances. A few systems also offer shore power direct-fired heater option. Table 5-21 shows a comparison of connections. Each of these systems provides 8 to 12 hours several fuel-operated heaters. of runtime. Because of this limited duration, they may not be ideal for applications that require longer term (weekend) Auxiliary Power Units heating or cooling. Table 5-20 compares a variety of systems currently available as identified by the U.S. EPA’s SmartWay Auxiliary power units (APUs) provide electricity and heat Web site.12 As shown, each system offers various features with the help of a small internal combustion engine equipped and each retails for $575 and $7,500. Both Kenworth and with a generator and heat recovery device. Cooling can be Peterbilt have introduced idle reduction systems on their provided with the installation of an electric air conditioner products. The Kenworth system is called Clean Power, and in the cab. Many APU devices are available. In addition to operators could see as high as 8 percent reduction in fuel those APUs compared in Table 5-22, Navistar announced in consumption. The system, however, depends greatly on the a press release:13 application. Operators with substantial heating requirements could see the benefit reduced to 1 to 2 percent. Both systems Operating at 4.2 kW, the MaxxPower APU equates to best- in-class fuel consumption of 0.18 gallons per hour. It features depend on the current battery capacity. Current systems use EPA Tier IV certification and is in the process of acquiring lithium-ion batteries, and manufacturers are looking at vari- CARB ’08 emissions compliance. Several states currently ous chemistries for future generations. There is an expecta- offer incentives for trucks with idle reduction systems. Pro- tion that the passenger car market will drive economies of duction is slated for later this year. scale and lower battery costs. (Note that APUs need to be emissions compliant to operate in Fuel-Operated Heaters California, which can be accomplished with the installation of a $3,000 diesel particulate filter.) Also known as direct-fired heaters, fuel-operated heaters APUs can also be fuel cell powered. This technology are available to heat the cab, engine, or both. These heaters requires hydrogen for fuel or a reformer system for carbon- based fuels and the system can achieve the same fuel con- 11 K.G. Duleep, Energy and Environmental Analysis, “Heavy Duty Trucks sumption improvement as conventional APUs. Fuel Economy Technology,” presentation to the committee, Washington, D.C., December 5, 2008. 12 See http:eps.gov/smartway/transport/what-smartway/idling-reduction- 13 S ee http://www.rueters.com/article/pressRelease/idUS213209+07- available-tech.htm. May-2008+BW20080507.

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 VEHICLE TECHNOLOGIES FOR REDUCING LOAD-SPECIFIC FUEL CONSUMPTION TABLE 5-20 Idling Reduction Technologies Autotherm Idle Free T-2500 Systems Energy Driver Reefer Kenworth Recovery Bergstrom Comfort Glacier Bay Link Clean Peterbilt Safer Sun Power Feature/Supplier System NITE Dometic System ClimaCab System Power ComfortClass Viesa Technologies Heats cab ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ Cools cab ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ Powers on-board ✓ ✓ ✓ appliances Circulates heated coolant ✓ from engine to heater coils Runs off of vehicle ✓ ✓ ✓ battery Runs off separate battery ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ pack Shore power connection ✓ ✓ ✓ Automatic start ✓ ✓ ✓ at engine off Automatic shut down ✓ ✓ ✓ Monitors system (coolant ✓ ✓ ✓ ✓ ✓ temperature, battery (cab only) voltage) Run time (hours) na 10 10-15 10 (heating) 10 10 8 8-12 12 (cooling) (cooling) Thermal storage cooler ✓ ✓ Direct fueled heater ✓ ✓ ✓ Weight (lb) 5 210 na 520 161 200 550 126 440 (not including batteries) Retail price $575 to $3,495 $3,500 to $6,895 $7,995 $1,600 $6,900 $710 $7,500 SOURCE: TIAX (2009), p. 4-91. TABLE 5-21 Comparison of Fuel-Operated Heaters Espar Heater System Webasto Product North America Automotive Feature/Supplier Climate Control Cab Engine Cab Engine Heats cab 4 models 2 models ✓ Manual or automatic control Yes Auto Auto Auto Battery-powered fuel-fired heaters ✓ ✓ ✓ ✓ ✓ Heats engine 2 models 3 models Fuel use 1 gal/24 hr 1 gal/20 hr 1 gal/4-6 hr 1 gal/20 hr 0.03-0.24 gal/hr Retail price $920-$1,200 $1,000-$3,000 $1,000-$3,000 SOURCE: TIAX (2009), p. 4-92. Truck Stop Electrification cessories. There are generally two types of electrified parking spaces: dual system and single system. A dual system re- There are currently 138 truck stops equipped with truck quires equipment on both the truck and the ground. A single stop electrification identified in the Alternative Fuel Data system requires equipment only at the truck stop. Table 5-23 Center Truck Stop Electrification database.14 Located in 34 shows a comparison of several truck stop electrification states, these sites provide truckers the opportunity to “plug- systems. As discussed in the National Research Council’s in” to power heaters, air conditioners, lights, and other ac - (NRC’s) review of the DOE 21st Century Truck Partnership (NRC, 2008), continuing efforts to standardize the electrical systems on trucks and at truck stops are needed. 14 See http://www.afdc.energy.gov/afdc/progs/tse_listings.php.

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES TABLE 5-22 Comparison of Auxiliary Power Units Heats 110V Auto- Supplier Heats Cab Cools Cab Engine FC (gal/hr) AC on Shorepower Cost Auxiliary Power Dynamics Yes Yes Yes 0.25 Yes Yes Black Rock Systems 26,000 Btu 26,000 Btu 0.20 or 0.30 $7,499 to $8,100 Carrier Transicold Yes Yes Yes 0.2 Yes Yes Yes Comfort Master 31,000 Btu 31,000 Btu 0.25 Yes Yes Yes $7,200 to $8,100 Craufurd Manufacturing 22,000 Btu 22,000 Btu Diamond Power Systems 14,500 Btu 14,500 Btu 0.26 Yes Yes Yes $6,500 Double Eagle Industries Yes Yes Yes 0.3 DC $7,000 to $9,000 Flying J Yes Yes Yes Yes Yes Yes $6,999 Frigette Truck Climate System Yes Yes Yes $6,000 to $7,500 Idlebuster Yes Yes Yes Yes Yes Yes $6,900 to $7,750 Kohler 10,000 Btu 12,000 Btu Yes Yes Kool-Gen Optional Yes Yes $6,925 Mechron Power Systems 5,000-10,000 Btu 10,000-14,000 Btu 0.21 Yes Pony Pack Yes Yes Yes 0.2 DC $7,500 Rig Master Power Yes Yes Yes 0.2 Yes $6,300 Star Class $5,995 to $6,500 Thermo King 13,000 Btu Yes Yes 0.04 to 0.14 Yes Yes $8,000 to $10,000 (+$3,000 DPF for California) TRIDAKO Energy Systems 30,000 Btu 24,000 Btu Yes 0.4 $8,499 Truck Gen Yes Yes 0.2 Yes Yes $6,000 to $7,000 SOURCE: TIAX (2009) p. 4-94. Idle Reduction System Comparison This is based on a SmartWay estimate for idle engine fuel consumption, and is consistent with a 4-kW ac- Idle reduction systems differ in a number of respects. cessory load with an engine operating at 15 percent ef- Some of the key discriminators are fuel use per time; func- ficiency. The 21st Century Truck Partnership estimates tionality (heating ability, cooling ability, and electric loads); a typical accessory load of 3 to 5 kW for a line-haul infrastructure requirements; and cost. These features are truck (NRC, 2008). It is possible that current engines summarized in Table 5-24 for each of the five idle reduction have lower idle fuel consumption rates. strategies examined. Cells that are shaded light green cor- • A line-haul truck is assumed to operate under hotel respond to favorable attributes; cells that are shaded yellow loads for between 1,500 to 2,400 hours per year. This correspond to mild drawbacks; and cells that are shaded dark range is meant to bracket the range between a medium- orange correspond to major drawbacks. The fuel-savings and high-mileage vehicle. benefits in Table 5-24 are estimated using the following • A line-haul truck is assumed to use 20,000 gallons of assumptions: fuel per year. • It was assumed that a direct-fire heater is in use for 600 • An idling engine consumes 0.8 gallons of fuel per hour. to 800 hours per year. SmartWay estimates 800 hours per year of heater fuel use.15 TABLE 5-23 Comparison of Truck Stop Electrification INTELLIGENT VEHICLE TECHNOLOGIES Systems IVT combines information about the state of the ve- Supplier Cost ($) Service Fee ($) hicle, the environment around the vehicle, and Telematics Dual Systems to provide assistance to the driver. Telematics refers to the Phillips and Temro 125 integration of Global Positioning System (GPS) technology Shurepower 200-2,000 0.50 per hour with computers and mobile communications technologies. Teleflex (Proheat) 2,500 Although IVT is commonly applied to active safety systems Xantrex 1,500, inverter/charger 2,500 per space 1,500, electric HVAC (i.e., crash avoidance and crash mitigation), for purposes of Single Systems this report the definition is broadened to specifically address Cabaire fuel consumption reduction. Craufurd Manufacturing 8,550 per space IdleAire Technologies 10, adapter 2.18 per hour retail 1.85 per hour fleet 15 S ee http:www.epa.gov/smartway/transport/calculators/calculator SOURCE: TIAX (2009), p. 4-93. explanation.htm.

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 VEHICLE TECHNOLOGIES FOR REDUCING LOAD-SPECIFIC FUEL CONSUMPTION TABLE 5-24 Comparison of Idle Reduction Systems SOURCE: TIAX (2009), p. 4-95. IVT-Enabling Technologies Adaptive Cruise Control Although computing technologies have advanced greatly Description. Adaptive cruise control (ACC) augments con- over the past decade, the most significant enablers for IVT ventional cruise control by sensing the traffic ahead with a are the advances in GPS and mobile communications. The radar or laser sensor mounted on the front of the vehicle. first step in the GPS modernization program occurred in May When there is no vehicle ahead, ACC operates the same as 2000 when the U.S. Department of Defense ended the use of conventional cruise control. However, when the forward- Selective Availability (SA). SA was an intentional degrada- looking sensor detects a vehicle ahead that is traveling at a tion of civilian GPS accuracy implemented on a global basis slower speed, the vehicle speed is slowed to the speed of the from the GPS satellites. Prior to its deactivation, civil GPS preceding vehicle through actuation of the throttle or mild readings could be off by up to 100 m. After SA was turned brake action. The appropriate separation distance between off, civil GPS accuracy instantly improved by an order of vehicles is then maintained automatically. The desired sepa- magnitude, thereby benefiting civil and commercial users ration distance can be set by the driver within limits and is a worldwide. In 2004 about 1 million fleet vehicles in the function of the vehicle speed. Typically, this is the distance United States were equipped with GPS devices (Murphy, the vehicle would travel in the range of 2 to 3 seconds. 2004). Anything significantly larger than that would likely result in Mobile communications, particularly cell phone usage, “cut-ins” by a third vehicle. has grown immensely in recent years. Cell phone users in the United States have increased from 50 million a little Applications. All vehicles that regularly travel on urban and over a decade ago to more than 250 million in 2007 (CIA, rural interstate roads. Adaptive Cruise Control systems are 2007). Many cell towers are located along the interstate available on current vehicles (primarily as a safety feature) system, which allows mobile travelers to have cellular but are not widely adopted. service even in the more remote rural regions of the United States. Cost. $1,100 to $3,000, depending on application and in- Dedicated Short Range Communications (DSRC) is a cluded features. block of spectrum in the 5.850 to 5.925 GHz band allocated by the Federal Communications Commission in 2003 to Benefit. Cruise control is a driver aid that relieves driver enhance the safety and productivity of the transportation workload and provides smooth acceleration and deceleration system. The DSRC service involves vehicle-to-vehicle and for navigating grades. In traffic, conventional cruise control vehicle-to-infrastructure communications, helping to protect is little used because a constant speed cannot be maintained. the safety of the traveling public. The band is also eligible The driver must therefore revert to manual control. ACC has for use by nonpublic safety entities for commercial or private fuel economy benefits because, even in traffic, all accelera- DSRC operations. tions and decelerations are smaller and have a smooth profile

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES Adaptive Cruise Control with Real-Time Traffic Information and there is little accelerator pedal “dither” compared to manual driving. A field operational test using 108 nonpro- Description. This concept utilizes real-time traffic informa- fessional drivers and 10 passenger cars equipped with ACC tion to anticipate changes in traffic speed and then adjusts in southeast Michigan (Koziel et al., 1999) indicated a 10 the set cruise speed accordingly to reduce large accelerations percent fuel consumption reduction compared with manual and decelerations. The real-time traffic data can come from driving. For professional drivers, the benefit is more likely imbedded loop detectors in the highway such as the Perfor- to be around 1 percent (TIAX, 2009, p. 4-99). mance Measurement System (PeMS) used in California17 or traffic probe vehicles that carry special cell phones able to Predictive Cruise Control communicate their position and velocity in real time. PeMS provides average traffic speed and density every 5 minutes Description. Predictive cruise control is an enhancement at a resolution of 0.3 to 3 miles. A communications link, of conventional cruise control whereby the current vehicle such as cell phones or SRDC, is required for the vehicle to location and topography of the upcoming road provided by acquire the traffic information from nearby vehicles or the a GPS receiver are used to calculate the target cruise speed infrastructure. within an upper and a lower limit. When a truck approaches a hill, the truck accelerates prior to beginning the climb. Applications. All vehicles that regularly travel rural and During the climb, the target cruise speed is continuously urban interstate roads. There is some usage in California, but calculated and the truck is allowed to slow to the lower limit. its low. There are currently no other commercial applications When approaching a downhill, the truck slows down prior to in existence. beginning the descent but is allowed to increase to the upper limit during the descent. Fuel savings accrue because there is Cost. No cost data are available. less need to accelerate while on the uphill climb and less time spent in the lower gears. In addition, less fuel is consumed Benefit. In research reported by Kohut et al. (2009), simula- compared to conventional cruise control during the downhill tions were run using real traffic speed data for a trip from phase because the truck is allowed to slow to a lower limit Palo Alto to San Jose, California, and validated vehicle and prior to the descent of a hill rather than maintaining a fixed engine models of a passenger car. The simulations calculated cruise speed. the reduction in fuel used when varying the look-ahead dis- tance of traffic flow. The simulations showed a 5 to 7 percent Applications. All vehicles that regularly travel on rural reduction of fuel for a trip time that changes 3 percent or interstate roads. Daimler Trucks of North America will be less when the look-ahead distance was varied from 1,200 offering this feature in 2009. to 2,000 m. Cost. $861 to $1,561, depending on type of vehicle.16 Predictive Control of Hybrid Electric Vehicles Benefit. The reduction in fuel consumption will vary de- Description. Real-world optimal fuel consumption for pending on the topography the truck is traveling. For ex- hybrid electric vehicles (HEVs) is possible using predictive ample, traveling on relatively flat terrain would yield little control based on GPS with a topographical database of the benefit. Traveling in the hills of Tennessee, on the other hand, road ahead and, possibly, real-time traffic information, and could yield significant fuel savings. Experimental results then controlling the power split ratio (PSR) of the internal reported by Hellstrom et al. (2007) show a 3.5 percent fuel combustion engine and the electric motor. The main control- use reduction without an increase in trip time for a Class ler uses current operating information such as battery state 8 truck traveling 150 km between Norrkoping and Soder- of charge, engine efficiency, and emission maps, to establish talje, Sweden, compared to conventional cruise control. the PSR at each instant. A navigation controller uses traffic Simulation results reported by Lattermann et al. (2004) of and GPS information to predict the future driving state of a 75,000 lb class 8 truck traveling on a 25 km stretch of I5 the vehicle and modifies the PSR to charge the battery (if, around Portland, Oregon, showed a 4 to 5 percent reduction for example, it is predicted that the vehicle will change from in fuel consumption with an increase in trip time of 0.3 to highway to city driving, where the electric motor will be re- 1.4 percent compared to conventional cruise control. Other quired) or to deplete the battery for improved fuel economy estimates would suggest an improvement of 1 to 3 percent in anticipation of a downgrade, where regeneration may be (TIAX, 2009, p. 4-99). expected (Kessels, 2007). 16 David 17 C alifornia Kayes, Daimler Trucks, personal communication, June 23, Performance Measurement System, h ttp://pems.eecs. 2009. berkeley.edu.

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 VEHICLE TECHNOLOGIES FOR REDUCING LOAD-SPECIFIC FUEL CONSUMPTION Browand et al. (2004) report on experiments conducted Applications. All HEV applications. Current commercial on two Freightliner 2001 Century Class trucks with 53-foot usage is unknown. van trailers. The tractors were engine-forward design. One vehicle was 32,000 lb and the other was 64,000 lb. At a con- Cost. Similar to that cost of predictive cruise control. stant speed of 55 mph, the measured fuel savings at a spacing of 10 m were 10 percent and 6 percent, respectively, for the Benefit. Simulation results reported by Rajagopalan and trail and lead truck. In the spacing range of 3 to 10 m, fuel Washington (2002), Johannesson et al. (2007), and Kim et al. consumption savings were in the range 10 to 12 percent for (2008) show a fuel economy improvement of 3 to 9 percent the trail truck and 5 to 10 percent for the lead truck, with the versus nonpredictive control. The SENTIENCE program larger values of savings occurring at the shorter spacing. described by Walker (2008), which is underway, is intended to provide much-needed validation of simulation results. Navigation and Route Optimization Electronic Tow Bar Description. In its simplest form, navigation and route optimization consists of an in-vehicle device that contains Description. The electronic tow bar is a concept whereby a GPS receiver, a database that includes map information a lead vehicle is driven manually and a following vehicle is and points of interest, and a display that allows the driver driven automatically by a vehicle controller that maintains to enter a desired destination and view the map. The device a set distance between the two vehicles. In a sense, it is then calculates a route based on one of several criteria, similar to ACC except that the gap between the lead and such as fastest time or shortest distance. While en route, the trailing vehicles is much smaller to take advantage of the driver receives visual and verbal turn-by-turn instructions aerodynamic drag reduction from the slipstream effect. Be- to the destination. Navigation devices specially designed cause of this small separation distance, typically one-half to for the trucking industry may have features that will inform one truck length, precise control must be maintained by the the driver about tolls, road restrictions, hazmat routes and trailing vehicle to prevent the vehicles from contacting if the preferred truck routes (e.g., parkways that do not allow lead vehicle suddenly brakes. Although this concept is not trucks, directions that do not require right-hand turns). In yet commercially available, the experimental hardware con- addition, it may include points of interest such as truck figurations described by Fritz (1999), Fritz et al. (2004), and stops, rest stops, weigh stations, and other services useful Lu et al. (2004) generally use radar, laser, or optical sensors to the driver. on the trailing vehicle to measure the separation distance. For the fleet operator, the route is usually planned in the In addition, vehicle-to-vehicle communications are used to back office using route optimization software and down- provide information on the state of lead vehicle (e.g., vehicle loaded to the vehicle either before the vehicle leaves the speed, acceleration, pedal position) to the vehicle controller terminal or while the vehicle is on the road. The route opti- in the trailing vehicle. This gives additional lead time to the mization software may reside on a single personal computer, trailing vehicle to respond to sudden accelerations or braking the fleet’s central computer, or a Web-based application and of the lead vehicle. has sophisticated algorithms that take into account historical traffic data as a function of time of day and up-to-date speed Applications. The electronic tow bar would be most ap- limits on the planned route. The planned route will yield a plicable to line-haul trucks using the interstate system. Al- path with minimum fuel consumed. It is also possible for the though it is possible to extend the concept to more than two fleet operator to provide immediate changes to its routes in vehicles, it is unlikely that this would be allowed, with the case of incidents such as road construction or weather-related possible exception of truck-only lanes. road closures. Dynamic vehicle routing differs from the static routing Cost. Anticipated costs of around $500 to $2,600 for addi- previously described in that it includes real-time traffic tional sensors and active safety features (Baker et al., 2009). information in addition to historical traffic data for comput- ing the optimized route. Real-time traffic information from Benefit. Bonnet and Fritz (2000) conducted experiments on imbedded loop detectors or traffic probe vehicles using two heavy-duty semitrailer Mercedes-Benz trucks of type smartphones allow the route planning software to do en route ACTROS 1853 LS, both having cab-over-engine design. The rerouting to avoid traffic congestion. This concept, relatively lead truck was 32,000 lb and the trail truck was 62,000 lb. new, has potential drawbacks in that the driver may not re- For the trail truck with the separation distance varied between ceive the new route in a timely manner to avoid the conges- 8 and 16 m, the fuel consumption reduction ranged from 15 tion or the alternate route may itself become congested due to 21 percent at 80 km/hour and from 10 to 17 percent at to the additional traffic. 60 km/hour when compared with the truck driving in isola- tion. For the lead truck, the fuel consumption reduction was Applications. Pickup and delivery applications, regional and between 5 and 10 percent at 80 km/h and between 3 and 7 long-haul operations, fleet operators. percent at 60 km/hour.

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES 2.5 percent are feasible. Electrification of these auxiliaries, Cost. Navigation device, between $400 and $800 plus mostly in hybrid vehicles, will reduce some of this loss. monthly service fees that range from $20 to $40 (TIAX, 2009, p. 4-98). Route optimization software starts at $10,000 (Bennett, 2008). Rolling Resistance Finding 5-6. Technological advances have lowered the co- Benefit. Bennett (2008) reports the case of a fleet operator efficient of rolling resistance of tires by roughly 50 percent where route optimization software reduced fleet mileage since 1990, but further reductions are expected to be less between 5 percent and 10 percent annually. For line-haul op- dramatic. The use of low rolling resistance tires, such as erations, which spend a comparatively small amount of time wide-based singles, show 4 percent to 11 percent reductions in congested driving conditions, the estimated fuel-savings in fuel consumption with models and on-road tests, depend - potential is up to 1 percent (TIAX, 2009, p. 4-98). ing on terrain, weight, and choice of baseline tire. FINDINGS AND RECOMMENDATIONS Finding 5-7. Tire pressure monitoring, automatic inflation systems, and nitrogen inflation are all effective in avoid- Aerodynamics ing wasting fuel due to underinflation and improve vehicle Finding 5-1. At highway speeds, aerodynamic loads con- safety. sume more power than any other load on current tractor- Recommendation 5-2. There are numerous variables that trailer vehicles. Aerodynamic features can significantly contribute to the range of results of test programs. An in- reduce these loads, but their value diminishes rapidly as dustry standard (SAE) protocol for measuring and reporting average vehicle speed goes down. In low-speed operation, the coefficient of rolling resistance is recommended to aid aerodynamic features have little value. consumer selection, similar to that proposed for passenger Finding 5-2. Four areas of the tractor-trailer combination car tires. have been identified as critical for achieving aerodynamic improvements: Vehicle Mass (Weight) Finding 5-8. Results from tests and computer models sum- • Tractor streamlining marized in this chapter show that the impact of weight on • Management of airflow around the tractor-to-trailer truck fuel consumption will range from 0.5 to 1.0 percent gap per 1000 lb on level roads to over 2 percent per 1,000 lb on • Management of airflow under the trailer hilly terrain and for driving cycles with frequent accelera- • Management of airflow at the rear of the trailer tions. These results are primarily for Class 8 combination Finding 5-3. By the 2015 to 2020 time frame, the use of trucks. For Class 8 trucks at full weight capacity, the pay- load-specific fuel consumption is reduced by about 2 percent aerodynamic features can provide fuel consumption reduc- per 1,000 lb. tions of about 15 percent for tractor-van trailer vehicles operating at 65 mph. The potential benefits for other classes Finding 5-9. Design progress and the use of lightweight of vehicles are significantly less. materials for major components, such as the engine, drive- Finding 5-4. Many tractor and trailer aerodynamic features train, wheels and tires, and chassis, have been estimated to save weight up to 20 percent beyond current technology by are damage prone in low-speed operation. The cost of re- the 21st Century Truck Partnership and separately by one pairing these features may be a significant barrier to imple- manufacturer. This could amount to as much as 5,000 lb over mentation for some applications, and broken aerodynamic the next decade. A fuel consumption reduction of about 5 components could become road hazards. percent could be achieved. Recommendation 5-1. R egulators should require that aerodynamic features be evaluated on a wind-averaged basis Idle Reduction that takes into account the effects of yaw. Tractor and trailer Finding 5-10. There are a number of technologies and prod- manufacturers should be required to certify their drag coef- ucts available for reducing idle fuel use in class 8 heavy-duty ficient results using a common industry standard. vehicles. It is reported that up to 9 percent fuel consumption reduction is available, but it is dependent on the hotel power Auxiliary Loads load factor. The committee has used 5 percent to 9 percent Finding 5-5. Auxiliary loads can consume up to 2.5 per- and TIAX used an average of 6 percent fuel consumption reduction potential. cent of fuel, so fuel consumption reductions of 1 percent to

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 VEHICLE TECHNOLOGIES FOR REDUCING LOAD-SPECIFIC FUEL CONSUMPTION Intelligent Vehicle Technologies tory. December. CARB (California Air Resources Board). 2008. Final Regulation Order to Finding 5-11. In general, intelligent vehicle technologies Reduce Greenhouse Gas Emissions from Heavy-Duty Vehicles. Avail- provide fuel consumption reductions by taking advantage able at http://www.arb.ca.gov/regact/2008/ghghdv08/ghgfro.pdf. Caterpillar. 2006. Understanding Tractor-Trailer Performance. Brochure. of knowledge of the vehicle’s location, terrain in the vicin- Available at http://ohe.cat.com/cda/files/867819/7/LEGT6380.pd f. ity of the vehicle, congestion, location of leading vehicles, Peoria, Ill.: Caterpillar. historical traffic data, and so forth, and altering the speed of CIA (Central Intelligence Agency). 2007. CIA World Fact Book. the vehicle, the route the vehicle travels, or, in the case of Cooper, K. 2004. Commercial vehicle aerodynamic drag reduction: His - hybrid electric vehicles, altering the power split ratio. This torical perspective as a guide. Pp. 9-28 in The Aerodynamics of Heavy Vehicles: Trucks, Buses, and Trains (R. McCallen, F. Browand, and J. fuel savings may not show up in any fuel consumption test. Ross, eds). New York: Springer. DOE (U.S. Department of Energy). 2006. 21st Century Truck Partnership Finding 5-12. A number of the technologies—adaptive Roadmap and Technical White Papers. Doc. No. 21CTP-003. Washing- cruise control, predictive cruise control, and navigation and ton, D.C.: DOE. December. route optimization—are being applied by the trucking indus- DOE. 2008. Areas of Loss in Typical On-Highway Vehicles, and/or Review. Washington, D.C.: DOE. try without any regulation because the owners and operators ECD (European Council Directive 89/297/EEC). 1989 Underride Protection view the reduction in fuel costs as good business. for Unprotected Road Users. April13. Available at http://eur-lex.europa. eu/LexUriServ/LexUriServ.do?uri=CELEX:31989L0297:EN:NOT. Finding 5-13. Based on experiments to date, the electronic Englar, R. 2005. The application of pneumatic aerodynamic technology to tow bar concept of trucks traveling closely spaced in tandem improve drag reduction, performance, safety, and control of advanced automotive vehicles. Proceedings of the 2004 NASA/ONR Circulation can provide significantly lower fuel consumption, 8 percent Control Workshop, Part 2, pp. 957-995. June. Available from http://ntrs. to 15 percent, compared with the same vehicles traveling nasa.gov/search.jsp?R=421681&id=4&as=false&or=false&qs=Ne%3D separately. 25%26Ns%3DHarvestDate%257c0%26N%3D255%2B32 EPA (U.S. Environmental Protection Agency). 2009. 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