Vehicle power demands are weight sensitive and encompass the engine power used to overcome inertia, rolling resistance, aerodynamic drag, drivetrain losses, and the power used for auxiliary loads. Figure 5-1 has often been used to summarize the vehicle power demands for a tractor-trailer with a gross vehicle weight (GVW) of 80,000 lb operating on flat terrain for 1 hour; the original paper used energy in units of kilowatt-hours (kWh) for each area rather than percentages (Woodrooffe and Vachon, 2000).
More recently, Figure 3-1 in Chapter 3 has been used to describe where the fuel energy goes. Beginning with 100 percent of the energy in the left hand bar, it moves to show the energy lost in the cylinder to heat and out through the exhaust. The middle column shows the energy lost to friction, pumps, and other accessories on the engine needed to meet emissions certification. The column titled “accessories” shows energy used for auxiliary loads such as air conditioning. The fourth column shows the energy lost through inefficiencies in the driveline, including the clutch, transmission, and axle. The fourth column shows the energy at the wheels and how it is used to propel the vehicle down the road or up a grade or to stop it.
Vehicle power demands are discussed in the NRC Phase 2 report (NRC, 2012). The present report provides an update1 and delineates the 21st Century Truck Partnership (21CTP) technology goals for each of the vehicle power demand areas addressed by the Partnership; the present report then addresses each of these areas in separate sections: (1) aerodynamics, (2) tire rolling resistance, (3) auxiliary loads, (4) weight reduction, (5) thermal management, and (6) friction and wear. It should be noted that there are a limited number of activities related to vehicle power demands under the umbrella of 21CTP since many of these areas are being addressed by the SuperTruck projects. Additional material related to vehicle power demands is found in Chapter 4 on hybrid vehicles and Chapter 8 on the SuperTruck program.
The previous report (NRC, 2012) and discussions in the industry focus on vehicle power demands from the net output of the engine while driving at highway speeds on level ground with a fixed load. The various uses of the engine power (overcoming rolling resistance, overcoming aerodynamic drag, power train losses, auxiliary loads) were categorized and sized along with details of their efficiency. As regulations for emissions and fuel consumption have advanced, the effects of energy density of the fuel used and the specifics of the drive cycle have become important. Fleets
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1 For this section of the report, the following presentations to the committee were the source of information: D. Anderson, “Vehicle and Systems Simulation and Testing,” September 2014; J. Gibbs, DOE Office of Vehicles Technologies, “NAS Review of VTO Materials Program in Support of 21CTP,”on September 3, 2014; A. Greszler, Vehicle Systems. Volvo Group Truck Technology, “SuperTruck: Development and Demonstration of a Fuel-Efficient Class 8 Highway Vehicle,” on May 15, 2014; D. Kayes, D. Rotz, and S. Singh, SuperTruck Team, Daimler Trucks North America (DTNA), on May 14, 2014; G. Fadler, Navistar, “Navistar Fuel Economy and Emissions,” presentation to the NRC Committee on Assessment of Technologies and Approaches for Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles, Phase 2, 2013; K. Howden, DOE VTO, “Overview and Update of 21CTP Responses to NRC Recommendations,” May 14, 2014; G. Keller, ANL, “Update on Idling Reduction Activities,” September 4, 2014; E. Koeberlein, Cummins/Peterbilt, “Cummins SuperTruck Program: Technology and System Level Demonstration of Highly Efficient and Clean, Diesel Powered Class 8 Trucks,” May 14, 2014; T. Reinhart, Southwest Research Institute, “Technologies for MD/HD GHG and Fuel Efficiency,” November 18, 2014; K. Stork, DOE Vehicle Technologies Office, “Overview of the DOE Fuel and Lubricant Technologies R&D,” September 3, 2014; Spears, Environmental Protection Agency and National Highway Traffic Safety Administration, “Looking Ahead to the Next Phase of Heavy-Duty Greenhouse Gas and Fuel Efficiency Standards,” September 3, 2014; V. Sujan, Cummins, Inc., “SuperTruck: Vehicle Modeling, Optimization and Cycle Management,” August 28, 2014; R. Zukouski, Navistar, “SuperTruck–Development and Demonstration of a Fuel-Efficient Class 8 Tractor and Trailer,” November 18, 2014. The following Annual Merit Reviews were also the source of information: Ajayi et al., 2014; Benedict, 2014; Birky, 2014; Cox, 2014; Deter, 2014; Fenske et al., 2014; Gonder, 2014; Kambiz, 2014; Karbowski et al., 2014; Kim and Rousseau, 2014; Lustbader, 2014; Lustbader and Kiss, 2014; Martin et al., 2014; Meyer, 2014; Rask, 2014; Rugh, 2014; Stephens, 2014; Walkowicz, 2014a, b.
FIGURE 5-1 Energy “loss” range of vehicle attributes as impacted by duty cycle, on a level road. SOURCE: NRC (2010), Figure 5-8.
continue to work to reduce fuel costs over their drive cycles using a variety of component technologies, including fleet management systems and systems to monitor and control driver behavior (Technology and Maintenance Council, 2014). There is a need for a reevaluation of the overall energy use for a vehicle. The committee believes it is more appropriately called the Vehicle Energy Demand Over a Drive Cycle.
Recognizing the changes that are occurring, the Partnership updated the goals for fuel consumption in the 2013 publication of its Roadmap and Technical White Papers (2013). The roadmap provides a description of a baseline for “average power use inventory” and forward- looking goals in Figures 5, 6, 7, and 8 of that document. These enhanced goals take into account the varying applications of Class 6 through Class 8 vehicles; are very specific in terms of the assumptions for weight; include idling fuel used; and use specific fuel consumption in energy units. However, the specification of drive cycles, including speed, terrain, and 24-hour operation, is less precise. Also, the goals do not include the effect of energy density of the fuel used and do not allow for other energy sources such as solar power or off-board electrical connections. This restatement of the goals in the white papers is a good step. In particular, it is the first attempt to specify load-specific fuel consumption and to take account of the current Environmental Protection Agency/National Highway Traffic Safety Administration (EPA/NHTSA) regulations on fuel consumption and greenhouse gas (GHG) emissions for medium- and heavy-duty vehicles (MHDVs) through model year 2018. Further work is needed to ensure research is done in the right areas to achieve real-world savings (NRC, 2014).
Finding 5-1. Current regulations for MHDVs on fuel consumption and load-specific fuel consumption are in place through model year 2018. The continuing improvement in reducing fuel consumption calls for a new baseline of vehicle energy demands over a drive cycle based on real-world operation. This new baseline would take into account such factors as load, grade, speed, torque, distance-based target schedules, and drive cycles over an extended period of time as well as rest periods required by law. The 21st Century Truck Partnership has taken a step forward in redefining a new baseline with the proposed average power use inventory in the 2013 roadmap and technical white papers.
Recommendation 5-1. The Partnership, through DOE and NHTSA, should work with the California Air Resources Board (CARB) and the trucking industry to work out a comprehensive new baseline for vehicle power demands (in kilowatt-hours) of a circa 2020 vehicle that include an extended period of operation.
GOALS AND SELECTED RELEVANT PROJECTS
The 21CTP Roadmap and Technical White Papers (2013) offer five technology goals for vehicle power demands.
Technology Goal 1: Develop and demonstrate advanced technology concepts that reduce the aerodynamic drag of a Class 8 highway tractor-trailer combination by 20% (from a drag coefficient of 0.69 to 0.55). Evaluate a stretch goal of 30% reduction in aerodynamic drag (from Cd=0.69 to Cd=0.48). The baseline for this goal is the proposed EPA/NHTSA baseline of Cd=0.69 with 9.2 m2 frontal area for a conventional Class 8 tractor with high roof sleeper.
Technology Goal 2: Develop and demonstrate low rolling resistance tires that can reduce vehicle rolling resistance and wheel weight for a Class 8 tractor-trailer. Demonstrate 35% reduction in rolling resistance from Crr=8.2 kg/metric ton for drive wheels to a goal of Crr=5.33 kg/metric ton. The
baseline for this goal is the EPA/NHTSA proposed baseline for a Class 8 tractor/trailer equipped with low rolling resistance dual tire drive wheel configurations having Crr=8.2 kg/metric ton.
Technology Goal 3: Develop and demonstrate technologies that reduce essential auxiliary loads by 50% (from current 20 horsepower to 10 horsepower) for Class 8 tractor-trailers. The baseline for this goal is a Class 8 highway tractor/trailer with sleeper operating 5 day over-the-highway operations at 36,000 kg (80,000 pounds) CGVW.
Technology Goal 4: Develop and demonstrate lightweight material and manufacturing processes that lead to a 10% reduction in tare weight for a 15,500 kg (34,000 pounds) tractor/trailer combination. Establish a long-term stretch goal of reducing combined vehicle weight by 20%. The baseline for this goal is a Class 8 highway tractor/trailer with high roof sleeper and dry van trailer capable of 36,000 kg CGVW.
Technology Goal 5: Thermal Management & Friction and Wear. Increase heat-load rejected by thermal management systems by 20% without increasing radiator size. Develop and demonstrate parasitic friction reduction technologies that reduce driveline losses by 50%, thereby improving Class 8 fuel efficiencies by 3%. The baseline for this goal is a Class 8 highway tractor/trailer with sleeper operating at steady state 65 mph at 36,000 kg CGVW.
The technology goals are well stated, specific, and measureable. A timeline of 10 years is given in Section 3 of the Roadmap and Technical White Papers, which takes the goals to 2023 from the date of publication (21CTP, 2013). Comments on the goals are relegated to the sections in this chapter that address the different technical areas.
In many ways, the efforts of the four SuperTruck projects are addressing many of the opportunities to reduce vehicle power demands. Nevertheless, there are continuing efforts associated with individual projects, mostly funded by DOE, that address these areas as well and which are the focus of this chapter. As pointed out in Chapter 1, the committee is not charged with reviewing every project in the 21CTP portfolio, but it has instead addressed a subset of key projects that were presented to it at its meetings, as well as information gathered from the DOE Annual Merit Review and other publications. Table 5-1 lists the projects affiliated with the 21CTP that are addressed in this chapter, with associated estimates of DOE funding for 2012-2014.
Aerodynamic losses, expressed in such terms as horsepower, are directly proportional to the coefficient of drag (Cd), the frontal area, and the velocity of the vehicle cubed (NRC, 2010, 2012). At highway speeds, especially above 50-60 mph, such losses are pronounced. However, fleets report slower overall speeds. A study by the Federal Highway Administration, Freight Performance Measurement: Travel Time in Freight-Significant Corridors (FHWA, 2005), shows speeds less than 60 miles per hour. As one would expect, the speeds near urban centers are often less, as documented in Freight Performance Measures Analysis of Freight-Significant Highway Locations–2013 (ATRI, 2013b). The distribution of speeds is significant for determining the potential for aerodynamic savings. The concept of a weighted aerodynamic-average speed (WAAS) (NRC, 2010) and the desire for real-world fuel savings (NRC, 2012) indicates the need for information on actual operation of vehicles.
The EPA SmartWay program turned 10 years old in 2014. In the spring of 2014, EPA announced a new program, SmartWay Elite Trailers (EPA, 2014). This moved the bar from a 5 percent reduction to a 9 percent reduction in fuel consumption from trailer aerodynamic devices and modified the test criteria to make them more repeatable and stringent. The EPA/NHTSA regulations for fuel consumption and GHG emissions could also address trailer aerodynamics and rolling resistance, as recommended in Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles (NRC, 2010). New products are being introduced into the market, including ones with aerodynamic improvements.2
While dry-van trailers are the most popular trailers, the concept work done by DOE on tanker trailer aerodynamics is a good step toward understanding how other trailer types can be improved (Kambiz, 2014).3 The project, Heavy Vehicle Aerodynamic Improvements (VSS006), at Lawrence Livermore National Laboratory (LLNL), had a budget of $900,000 in FY 2013 and $600,000 in FY 2014. Its objective was to provide guidance to industry to improve the fuel efficiency of Class 8 tractor-trailers and tankers through enhanced aerodynamics. Project VSS006 proposed an integrated tractor-trailer design, new from the ground up, that radically decreases aerodynamic drag and improves fuel efficiency. It designed a first-generation integrated tractor-trailer geometry and performed wind tunnel tests of selected aerodynamic devices to improve fuel efficiency. Plans are to conduct scaled experiments to design and validate the performance of aerodynamic treatments of an integrated tractor-trailer including improving the aerodynamics of tankers. Accomplishments to date include full-scale wind tunnel testing of two tractors, three trailers, and 23 devices. DOE has also completed testing on a track and collected on-the-road performance information. Funding for FY 2015 and beyond was not discussed. The proposed focus on improving the aerodynamics of trailer configurations other than dry vans is
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2 Vehicle OEMs have introduced new products with aerodynamic improvements in the last 2 years. Several announcements include DTNA’s Freightliner Cascadia Evolution and its Western Star 5700 XE; the Kenworth T680; Peterbilt’s 579 EPIQ; Volvo Trucks’ 2016 VN; and the Navistar ES.
3 Also, D. Anderson, “Vehicle and Systems Simulation and Testing,” presentation to the committee, September 2014.
TABLE 5-1 DOE Funding for Selected 21CTP Projects Related to Vehicle Power Demand (dollars)
| Public Review Project Title | Project ID | 2012 Funding | 2013 Funding | 2014 Funding | Note |
| DOE/DOD Parasitic Energy Loss Collaboration | VSS005 | 250,000 | 200,000 | 170,000 | |
| DOE’s Effort to Reduce Truck Aerodynamic Drag through Joint Experiments and Computations | VSS006 | 650,000 | 900,000 | 600,000 | |
| Development of High-Power-Density Driveline for Vehicles | VSS058 | 350,000 | 300,000 | 350,000 | |
| CoolCab Test and Evaluation and CoolCalc HVAC Tool Development | VSS075 | 225,000 | 700,000 | 300,000 | |
| Materials Approach to Fuel Efficient Tires | VSS084 | 186,000 | 675,000 | 167,000 | Project to end in FY 2014 |
| System for Automatically Maintaining Pressure in a Commercial Truck Tire | VSS085 | 571,189 | 713,810 | 161,535 | Project will end in FY 2015 |
| Aerodynamic Lightweight Cab Structure Components | LM060 | 365,000 | 280,000 | 65,000 | |
| Improving Fatigue Performance of AHSS Welds | LM062 | 355,000 | 125,000 | 150,000 | |
| Fleet DNA | VSS119 | 400,000 | 500,000 | 325,000 | |
NOTE: See Appendix D for complete list of projects associated with 21CTP. AHSS, advanced high-strength steel; HVAC, heating, ventilation, and air conditioning.
good and should include actions that can be taken to improve existing trailers, not just new trailers.
As for Technology Goal 1, which relates to aerodynamic drag, it could go further by taking into account the achievements of the SuperTruck program (a 40 percent improvement from a 2009 vehicle baseline) and current product offerings. While public information on the Cd for commercial vehicles is not readily available, with current regulations for GHGs and load-specific fuel consumption, it should be possible to estimate current values from the greenhouse gas emissions model (GEM) data, or to gather data on the Cd of commercial vehicles.
Response to Recommendations from NRC Phase 2 Review
R5-1 NRC Phase 2 Recommendation 5-1. Vehicle Aerodynamics: The Partnership should consider setting an aerodynamic drag stretch goal of 40 percent instead of 30 percent.
21CTP Response: The Partnership is aware of the NRC’s recent work on heavy truck fuel consumption for EPA and NHTSA and the results of that work. The Partnership’s work acknowledges the importance of trailers to the operational efficiency of the vehicle, and has made efforts to include trailer efficiency considerations in its SuperTruck research activities, from a vehicle systems perspective. The Partnership periodically reviews its goals and objectives to ensure they are in alignment with current technology progress and government agency research plans. SuperTruck research results will help inform future aerodynamic goal revisions. As information about the technology status of the aerodynamics work within SuperTruck becomes available, the Partnership will re-examine its goals for aerodynamics and adjust as necessary to provide the appropriate stretch targets.
Committee Comment on 5-1
The Partnership has not accepted a 40 percent stretch goal and has put the greatest part of its effort into the SuperTruck program. This program is focused on an idealized tractor-trailer combination rather than a real-world mix of tractors and trailers. It is indeed possible for improvements in the tractor aerodynamics to result in increased fuel consumption if the tractor is connected to a nonoptimized trailer. While not accepting the stretch goal, the Partnership’s new goals are based on the EPA/NHTSA regulatory numbers, which set out the Cd and frontal area requirements in specific numbers.
Finding and Recommendation
Finding 5-2. The research on aerodynamics, in the SuperTruck program and at LLNL, has focused on idealized, integrated tractor-trailer configurations of both dry van and tanker configurations. It has provided useful data that are influencing current and future designs to achieve reduced aerodynamic drag and fuel consumption. Since trailers have long useful lives (15-20 years), research on modifications to existing trailers is needed to accelerate fuel consumption savings.
Recommendation 5-2. The technology goal and research aerodynamics should focus on achieving a Cd of 0.48 for a new high-roof sleeper tractor pulling a new or existing trailer that is certified to be SmartWay Elite.4
Tires are critical to both safety and fuel consumption. Tire pressure, tread design, temperature effects, sidewall strength, durability, and materials are some of the factors that must be considered. Rolling resistance will continue to be a power demand for a Class 8 vehicle driving down the road at highway speeds. A reduction in fuel consumption with a 30 percent reduction in rolling resistance is possible based on research sponsored by NHTSA in support of the Phase 2 regulatory effort on fuel consumption and GHGs for MHDVs.5
A figure from Michelin included in the NRC Phase 2 report (2012) shows rolling resistance for tires in different axle positions on the vehicle. An update to this was presented to the NRC Committee on Technologies and Approaches for Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles, Phase 2, in November 2013.6 It shows the biggest improvement in drive axle tires, with a reduction in the coefficient of rolling resistance (Crr) of 9.5 percent. However, it shows an increase in Crr for the steer axle. This could be due to the regulations for reduced stopping distance, which put additional constraints on the steer axle weight. Figure 5-2 does suggest that wide-based single tires could achieve a Crr of about 5.3, a 20 percent improvement over the Crr of 6.6 listed for the drive axle. It appears that it will take considerable effort to achieve a Crr of less than 5 kg/tonne. It should be emphasized that an important design trade-off is to understand the effect on stopping distance as the rolling resistance is reduced, along with consideration of other tire design factors.
Two projects related to tire rolling resistance that the Partnership notes fall under the 21CTP umbrella were reported at the DOE Annual Merit Review in 2014—namely, Project VSS084 (Martin et al., 2014) and Project VSS085 (Benedict, 2014).
The project VSS084, A Materials Approach to Fuel Efficient Tires, is exploring the use of both tire barrier coatings and tire filler. This project at PPG Industries is a way to improve the tire rolling resistance and overall fuel efficiency by at least 2 percent. Goodyear will be involved in the evaluation work. The goal of the coatings work is improved fuel efficiency by maintaining tire pressure. The goal of the filler work is improved tread wear without increasing rolling resistance. Currently candidate fillers are under evaluation by Goodyear. A barrier coating has been applied to tires. This project was started in October 2011 and ended in September 2014. The total project funding was $2,046,503; the DOE part is $1,485,851.
The project VSS085, System for Automatically Maintaining Pressure in a Commercial Truck Tire, aims to improve fuel use through maintenance of tire inflation. Other aims will be to extend tire life and improve safety. Technical accomplishments to date include component optimization, laboratory testing, and on-vehicle system testing. The project started in October 2011 with an end of May 2015 but it was extended through June 2016. The budget provided by DOE is $1,499,771; Goodyear provided $2,572,953 (Benedict, 2014).
Tire rolling resistance can easily vary ±5 percent when inflation pressures vary by ±20 percent (Figure 5-3). Kleffmann7 also discussed the impact of rib pattern, winter tread pattern, tread depth, and footprint. Work is accordingly needed to address tire pressure maintenance and monitoring and inflation systems. The North American Council for Freight Efficiency (NACFE) has published a tire pressure systems confidence report (NACFE, 2013).
Response to Recommendations from the NRC Phase 2 Review
NRC Phase 2 Recommendation 5-2. Wide-Base Single Tires and Rolling Resistance Goal: The DOE should set the goal for reduced rolling resistance for the tires of the combination tractor-van trailer, rather than for the tractor drive wheels only, since improved-performance trailer tires are equally important to realizing the full benefit of reduced rolling resistance designs. This benefit can be achieved by combining the EPA base values
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4 A SmartWay Elite trailer is an EPA-designated 53-ft box dry-van or refrigerated trailer that achieves 10 percent or more fuel savings compared to a traditional trailer. Nine percent of the reduction comes from aerodynamic devices.
5 T. Reinhart, SouthWest Research Institute, “Technologies for MD/HD GHG and Fuel Efficiency,” presentation to NRC Committee on Assessment of Technologies and Approaches for Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles, Phase 2, April 29, 2014.
6 S. Lew, Michelin North America, Inc., “Test Methods for Truck Tire Rolling Resistance and Reducing Fuel Consumption of M-D and H-D Vehicles,” Presentation to the Committee on Assessment of Technologies and Approaches for Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles, Phase 2, on November 21, 2013.
7 Jens Kleffmann, Continental, “Effect of Tire Inflation on Rolling Resistance,” Presentation to NRC Committee on Assessment of Technologies and Approaches for Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles, Phase 2, on November 21, 2013.
FIGURE 5-2 Some ranges of Crrs for heavy truck tires. SOURCE: S. Lew, Michelin North America, Inc., “Test Methods for Truck Tire Rolling Resistance and Reducing Fuel Consumption of M-D and H-D Vehicles,” Presentation to the Committee on Assessment of Technologies and Approaches for Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles, Phase 2, on November 21, 2013. NOTE: The Crr is dimensionless and can be expressed as kg/tonne or newton/kilonewton.
FIGURE 5-3 Typical dependency of rolling resistance on inflation pressure for a 22.5 in. tire. SOURCE: J. Kleffmann, Continental, “Effect of Tire Inflation on Rolling Resistance,” Presentation to NRC Committee on Assessment of Technologies and Approaches for Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles, Phase 2, November 21, 2013.
for steer and drive tires in the EPA/NHTSA GHG rule, with an assumed trailer tire Crr value of about 0.0072.
21CTP Response: The Partnership concurs that a systems view of tire rolling resistance (including both tractor and trailer tires) is important to realizing the benefits of these tire technologies, and will take this into consideration when reviewing and revising Partnership goals. DOE, as a member of the Partnershi¡p, has initiated three tire technology projects in FY2012 (crosscutting between light duty and heavy duty vehicles) that target 2% fuel consumption reduction for the full vehicle from rolling resistance improvements and automatic tire inflation.
Committee Comment on Response to 5-2
The Partnership has not specifically addressed trailer tires. However, the EPA SmartWay and SmartWay Elite programs do address trailer tires (Waltzer, 2014). At the 2015 SAE government/industry meeting, Anthony Erb of EPA presented test data confirming the relationship between reductions in rolling resistance and the amount of fuel decrease to be expected (Erb, 2015). Roughly a 10 percent reduction in rolling resistance provides a 2-3 percent improvement in fuel consumption on test road conditions according to SAE fuel consumption test procedures. Real-world savings will be less.
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NRC Phase 2 Recommendation 5-3. Wide-Base Single Tire Retrofits: The 21CTP should consider producing a comprehensive summary that can be updated giving the prescriptions and precautions that carriers should consider when retrofitting NGWBSTs onto original equipment axles fitted with dual wheels and tires. This effect might best be managed in conjunction with the American Trucking Associations’ (ATA’s) Technology and Maintenance Council, which has drafted such a Recommended Practice and is a specialist in creating directives for ATA membership (ATA, 2007).
21CTP Response: The Partnership agrees that safety is extremely important when considering retrofits of NGWBS tires on existing trucks. The Partnership would encourage the use and promotion of Technology and Maintenance Council Recommended Practices to address this issue, and will consider addressing relevant safety concerns in the white papers and other 21CTP documentation addressing the use of next-generation wide-base single (NGWBS) tires.
Committee Comment on Response to 5-3
The Partnership expressed agreement with this recommendation, but specific examples of providing information are not known. The NRC (2010) report on medium- and heavy-duty vehicles addressed tires in general and tires for trailers in particular in Chapter 6. Next-generation wide-based single (NGWBS) tires are addressed, including barriers to further adoption of this technology. Based on presentations during that study, there has been improvement in the rolling resistance of dual tires as well.
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NRC Phase 2 Recommendation 5-4. Wide-Base Single Tires Rolling Resistance Test Procedure: The 21CTP, strongly supported by DOT and EPA (the latter through its SmartWay program), should conduct an authoritative study of the several barriers (e.g., related to tread life, truck stability in blowouts, run-flat tires, and other topics) to the widespread carrier adoption of next generation wide base single (NGWBS) tires. The DOT should specifically support reduction of barriers to NGWBS tire acceptance by requiring the universal use by tire manufacturers of a rolling resistance test procedure like that in ISO (International Organization for Standardization) 28580, to ensure that comparative inter-laboratory data exist.
21CTP Response: The Partnership agrees that identifying and addressing barriers to NGWBS tire acceptance are critical in expanding the use of this technology to improve truck efficiency. The Partnership will consider the possibility of conducting a study of barriers, subject to available resources. Truck tire manufacturers at present do not correlate rolling resistance measurements among one another to any large extent: this may be due to the fact that rolling resistance has not been a specification provided to tire manufacturers by the vehicle OEMs. (In the case of light-duty tires, the vehicle OEM considers tire rolling resistance to be a very important performance requirement.) This may change as new truck fuel consumption regulations are imposed, and the need for lower rolling resistance tires increases. It should be noted that the ISO 28580 standard calls for a reference laboratory, but this has not yet been identified. The Partnership agrees that lack of consistent rolling resistance measurement could be a barrier to increased acceptance of NGWBS tires, along with the lack of education for fleets and owner-operators on the benefits of low rolling resistance tires. Absent any requirements to provide rolling resistance information at the point of sale, this information is not generally available to the tire purchaser.
Committee Comment on Response to 5-4
The Partnership acknowledged the issue of consistent determination of rolling resistance among manufacturers and using ISO 28580 as important, but it took no action. As a result of the NHTSA/EPA GHG 2014 regulations requiring rolling resistance as an input to the GHG emissions model (GEM) for MHDVs, vehicle OEMs responsible for these vehicles have worked with the tire manufacturers to resolve this issue (NRC, 2014).8
Finding and Recommendations
Finding 5-3. Tire technology and design are heavily invested in by the private sector and will continue to be worked on as NHTSA and EPA implement fuel consumption regulations for MHDVs.
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8 S. Lew, Michelin North America, Inc., “Test Methods for Truck Tire Rolling Resistance and Reducing Fuel Consumption of M-D and H-D Vehicles,” Presentation to the Committee on Assessment of Technologies and Approaches for Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles, Phase 2, on November 21, 2013.
Recommendation 5-3. Although fuel consumption can be reduced with reductions in tire rolling resistance, the limits to such reductions must be carefully weighed against tire traction and the ability of vehicles to attain safe stopping distances. Technology Goal 2 should be revised to include an analysis of the impact of reduced aerodynamic drag as well as a metric for the ability to safely stop the vehicle within current regulations. The Partnership should work to make tire rolling resistance data available to retail purchasers.
Recommendation 5-4. The Partnership should assess the current proprietary research being conducted by tire manufacturers to determine what gaps, if any, need to be filled by government-sponsored research. The focus should be on analytical tools that can be used to quantitatively assess results and identify directions for further improvements in low rolling resistance, traction for starting, stability control, stopping distance, tire inflation, life, and retreading.
Auxiliary and accessory loads will become more important in the future as regulations tighten and improvements are made in the engine and other parts of the vehicle. A clear definition of what constitutes an auxiliary load is needed to focus efforts and to avoid double counting improvements. Multiple definitions exist in the report Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles (NRC, 2010). One definition related to Figure 4-1 in that report suggests that accessories are traditionally gear- or belt-driven by a vehicle’s engine (examples include the water pump, air compressor, power-steering pump, cooling fans, and the air-conditioning system). Another reference noted in Figure 5-1 says that accessories are essential to engine operation, such as the fuel pump, water pump, and oil pump, while auxiliary loads are accessories used in a vehicle’s operation, such as power steering, an air compressor, a cooling fan, and an air-conditioning compressor (NRC, 2010). This suggests that several items may be thought of as both an accessory and an auxiliary load.9 Even though the engine is controlled by various electronics with sensors and actuators, the alternator is not part of this test, because the electronics are run from an off-board power source. In 2013, the Partnership introduced its roadmap and technical white papers, including the concept of “essential auxiliary loads” without a full description of the terminology (21CTP, 2013). The Truck and Engine Manufacturers Association (EMA) has been contacted to clarify the issue of what is included in the certification of an engine and what is an accessory (see regulatory reference quoted in the Annex at the end of this chapter). Of significance is the statement, “use good engineering judgment to simulate all engine work inputs and outputs as they typically would operate in use.” This statement leaves open to estimates and engineering judgment several of the accessory loads on the engine and auxiliary loads on the vehicle.
Irrespective of whether something is an accessory or an auxiliary load, Project VSS133, “Cummins MD & HD Accessory Hybridization CRADA” (not included in Table 5-1) is addressing electrification of auxiliary loads (Deter, 2014; see Chapter 4). It was started in July 2013 and was scheduled to have ended in July 2015. It appears to be behind schedule as only 15 percent completion was reported in the 2014 Annual Merit Review (AMR), and a portion of spending is expected to be completed in the first half of 2015. Progress on this project is intertwined with the progress on Project VSS035, the Vehicle Systems Integration (VSI) project at Oak Ridge National Laboratory (see Chapter 4). The focus of that project is more to address hybrid certification testing options for hybrids for the next phase of regulations. It does not appear to address whether the models conform to real-world results.
Response to Recommendations from the NRC Phase 2 Review
R5-5 NRC Phase 2 Recommendation 5-5. Auxiliary Power Demands R&D: The Partnership should renew R&D efforts to further reduce fuel consumption related to auxiliary power demands.
21CTP Response: The Partnership should monitor auxiliary load improvements resulting from the SuperTruck projects.
Committee Comment on Response to 5-5
The Partnership has improved the description of its goals related to auxiliary loads by specifying that the 50 percent improvement is from a baseline of 20 horsepower to 10 horsepower and by updating the power use inventory. The SuperTruck program defines a 24-hour cycle of use that addresses auxiliary power demands related to hotel loads. Some SuperTruck teams have addressed other loads such as the air compressor and power steering system. More work is needed in this area. In particular, auxiliary power demands need to be better defined to avoid excessive claims of percentage improvements by suppliers.
Finding and Recommendation
Finding 5-4. The inconsistency in definitions of parasitic, accessory, essential auxiliary, and auxiliary loads creates confusion around assessments of where improvements can be made. The relative contribution of such loads will increase in the future.
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9 Dave Merrion, Chairman of Merrion Expert Consulting, LLC, suggests an accessory is a load needed to pass the engine certification test (personal communication, January 14, 2015).
Recommendation 5-5. The 21st Century Truck Partnership should work with EPA, NHTSA, and CARB to establish a clear definition of items included in the categories of accessory and auxiliary loads. Such clarification is needed to make an informed decision about which areas would be appropriate for government-sponsored research.
Truck weight reduction affects fuel consumption by reducing tire rolling resistance and unrecovered energy used when accelerating or climbing a grade. The energy required to overcome resistance is approximately linearly dependent on the weight of the vehicle. A fully loaded tractor-trailer combination can weigh up to the standard federal highway limit of 80,000 lb (weights as high as 164,000 lb are allowed in some states). Reduction in overall vehicle weight could enable an increase in freight delivered on a ton-mile basis, enabling more freight to be delivered per truck and improving load specific fuel consumption (LSFC). New vehicle systems (such as hybrid power trains, fuel cells, and auxiliary power units) will present complex packaging and weight issues that will further increase the need for reductions in the weight of the body, chassis, and powertrain components in order to maintain vehicle functionality.
Opportunities for fuel efficiency impact vary considerably by truck type and class and duty cycle. Vehicle weight effects are more important for duty cycles with frequent starts and stops (NRC, 2010, Table 5-16). For urban delivery vehicles, a 10 percent reduction in weight can reduce fuel consumption by as much as 7 percent. Before FY 2007, numerous DOE projects had been aimed at vehicle weight reduction; several projects involving the national laboratories and industry led to useful examples of such reduction. Owing to budget reductions, no funding was provided for lightweight materials (other than propulsion materials) from FY 2007 through FY 2009 for meeting 21CTP goals. However, beginning in late 2010, funding was once again provided for weight reduction projects, primarily in the SuperTruck program (see Chapter 8).
Incentives for Vehicle Weight Reduction
Reducing the weight of Class 8 trucks is important as trucks have been adding weight, particularly with emissions-compliance devices; emissions control components have added as much as 400 lb to a typical tractor.10 Aerodynamic devices, especially trailer devices, are growing in popularity, too, adding several hundred pounds in some cases. Weight reduction is also needed to offset other components such as auxiliary power units (~400 lb) added to reduce fuel consumption normally expended during idle. As selected truck-tractor technologies are expected to build on the EPA SmartWay configurations, some weight increase will be encountered—for example, with the use of tractor aerodynamic components and idle reduction components, as was just mentioned.
Weight reduction is beneficial if it can be reliably translated into more freight to be carried or reduced fuel consumption. Vehicles carrying freight in or on a trailer can either reach the maximum allowable weight for the vehicle or road before the available cargo space is filled (weigh out) or fill the available cargo space before reaching the weight limits (cube out). Vehicles that weigh out (before weight reduction) should see an improvement in LSFC, with more freight hauled for the same fuel consumed. Vehicles that cube out (before weight reduction) should see an improvement in load specific fuel consumption with the same freight hauled for less fuel consumed. Figure 5-4 indicates this bimodal split of gross vehicle weight in trucks on the road. Historically, bulk haulers and others that weigh out value the weight reduction more than those fleets that cube out.
In support of the overall goal to enable trucks and other heavy vehicles to be more energy efficient and to use alternative fuels while reducing emissions and remaining cost effective, the 21CTP seeks to reduce energy losses due to the weight of heavy vehicles without reducing vehicle functionality, durability, reliability, or safety. In addition, the 21CTP recognizes that improved materials may enable implementation of other technologies that can further improve the vehicle fuel efficiency (21CTP, 2013).
Weight Reduction Goals
Weight reduction goals vary according to the weight class of the vehicle; the targets for all classes range between a 10 percent and a 33 percent reduction in weight. Technology Goal 4 aims for a 10 percent reduction in tare weight for a 15,500 kg (34,000 lb) tractor-trailer combination, with a long-term stretch goal of reducing combined vehicle weight by 20 percent.
The weight targets for each vehicle class depend on performance requirements and duty cycle, with the targets reflecting the goal for total vehicle weight. The 21CTP recognizes that in some cases the weight reduction in the body and chassis will likely be higher. It is important to note that materials or technologies developed for a particular vehicle class are not necessarily limited to use in that class. For example, materials developed for lightweight frames for pickup trucks, vans, or sport utility vehicles (SUVs) will eventually be used in Classes 3-5 vehicles, and materials developed to meet the demanding performance requirements for Classes 7 and 8 trucks will find application in smaller vehicles (21CTP, 2013).
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10 Although MAP-21 (passed in 2012) allowed a federal exemption of up to 550 pounds for an APU, many roads are controlled by state regulations. A 400-lb exemption is the most common, as noted by the map of exemptions across the country found here: http://energy.gov/eere/vehicles/map-staterecognition-auxiliary-power-weight-exemption.
FIGURE 5-4 Bimodal distribution of truck gross vehicle weight (GVW) for five-axle vehicles from Weigh-In-Motion (WIM) data 421. SOURCE: Quinley (2010).
As noted by the Partnership, there has recently been “increased focus on manufacturing technologies that reduce the cost penalty associated with more expensive lightweight materials by conducting research in manufacturing technologies that are adaptable to the lower production volumes associated with heavy-duty commercial vehicles” (21CTP, 2013). In the committee’s opinion, weight reduction must not sacrifice the durability, reliability, or performance of the vehicle. Achieving these goals by reducing inertial loading will lead to substantial benefits: increased fuel efficiency with accompanying reductions in emissions; increased available payload capacity for some vehicles; reduced rolling resistance; optimized cab and chassis mechanical structures for crash worthiness; and aerodynamic drag reduction systems.
Opportunities and Initiatives
Current materials in Class 8 trucks offer numerous opportunities for reducing vehicle weight by introducing aluminum alloys (25-55 percent weight reduction), magnesium alloys (40-70 percent weight reduction), carbon fiber composites (30-65 percent weight reduction), and high-strength steels (15-25 percent weight reduction), albeit often at a cost premium. The more obvious opportunities lie in the body structure (~19 percent of total tractor weight), the chassis/frame components (~12 percent), and wheels and tires (~10 percent). Truck manufacturers have been substituting lightweight materials for a number of components in the cab, chassis, and wheels. Examples include composite structure in the cab, aluminum panels, aluminum wheels, and aluminum fuel tanks. Weight-reduction opportunities will also be afforded by the extensive use of aluminum for both tractors and trailers (NRC, 2010, Figure 5-38).
For example, in one project, LM060, (“Aerodynamic Lightweight Cab Structure Components,” from the 2013 VTO annual progress report (DOE, 2014), manufacturing methods for lightweight materials are being demonstrated that will increase the efficiency of Class 8 trucks by enabling
more widespread use of weight-saving Al and enabling aerodynamic styling by a new approach to Al sheet forming. The project will ultimately develop forming technology that enables Al sheet to replace steel sheet, which, together with molded fiberglass-reinforced composite panels and components, will provide individual panel and component weight savings of approximately 40 percent (Smith, 2014). Pacific Car and Foundry Company (PACCAR), the Pacific Northwest National Laboratory (PNNL), and Magna are working on aerodynamic lightweight cab structure components. PACCAR Technical Center engineering staff completed the design review and material specifications for the production A-pillar component that will be used to demonstrate the advanced forming process for an aerodynamic cab structure. The A-pillar component consists of left- and right-hand parts, and the complexity of the part exceeds the conventional forming limits of Al sheet alloys. As a result, the current part is produced from sheet molding compound (SMC), which has approximately a 40 percent weight penalty compared to Al. PNNL and PACCAR completed the selection of a Tier 1 supplier to develop the prototype A-pillar forming process and placed a cost-shared subcontract with Magna’s Stronach Centre for Innovation (SCFI). Magna will develop tooling and the forming process capable of producing the A-pillar component and deliver 25 each of left- and right-hand A-pillar parts to PNNL/PACCAR. Magna completed the forming analysis and simulation of a hybrid hot-forming/cold-stamping process capable of forming the A-pillar component in the X608 Al alloy. Based on the forming analysis, a prototype forming tooling has been designed and is being fabricated. In the coming years, fabrication of prototype aerodynamic formed components will be completed to deliver 25 left- and right-hand A-pillar parts for testing by PACCAR; and production feasibility for Al components in conjunction with Magna SCFI and PACCAR will be established.
In another example, DOE initiated a project that addresses advanced high-strength steel (AHSS) welds—ORNL Project LM062 (Improving Fatigue Performance of AHSS Welds). This project started in March 2011 and was scheduled to have ended in September 2014. The total project funding projection is $1,250,000 (DOE) and $650,000 (contractors). Downgaging of AHSS for weight reduction causes increased stress in the weld region. The objective of this project is weld residual stress mitigation to improve the fatigue performance of the weld joint of AHSS for high-volume vehicle production. Research has revealed the role of weld start-stop in controlling weld fatigue in short stitch welds. Microstructure-property modeling was used to increase understanding of the weld process. A special weld wire was developed, and weld fatigue life was improved by stress management. An in situ strain measurement technique was developed to directly measure the strain field during welding.
The SuperTruck projects, discussed in Chapter 8, are also developing and demonstrating several ways of reducing the weight of heavy-duty trucks by use of lightweight materials and advanced fabrication technologies. As discussed in the introduction to this chapter, current regulations for fuel consumption and greenhouse gas emissions are now based on load specific fuel consumption. Therefore, a key goal for weight reduction is translating it into usable freight that can be transported. This opens the possibility for increasing the amount of freight that can be moved within the confines of existing trailers. The industry has recognized this and has begun developing thinner walled trailers, wider doors, alternative flooring options, and techniques for stacking more freight into dry van trailers.
Findings and Recommendation
Finding 5-5. The SuperTruck teams achieved overall vehicle weight reductions, despite adding a number of fuel-saving features that increase weight (see Chapter 8). Unfortunately, many of the weight reduction technologies employed in SuperTruck are unlikely to prove cost effective. The Partnership goal of a 10 percent reduction in tare weight for a 15,500 kg tractor/trailer combination remains a good target, but cost effectiveness will be the challenge.
Finding 5-6. It is unknown what portion of full vehicles operate at the weight limit, what portion of vehicles are fully loaded but below the weight limit, and what percentage of vehicles are empty or only partly loaded. Understanding these factors is key to being able to determine the fuel savings available from weight reductions, and to understanding the cost-effectiveness of weight reductions or of increases in available cargo volume.
Finding 5-7. Weight reduction translates into more freight to be carried or fuel consumption reductions. Vehicles that weigh out (before weight reduction) see an improvement in load-specific fuel consumption (LSFC) with more freight hauled for the same fuel consumed. Vehicles that cube out (before weight reduction) see an improvement in load-specific fuel consumption with the same freight hauled for less fuel consumed.
Recommendation 5-6. The Partnership should initiate a study to determine what proportion of vehicle miles are run grossed-out, cubed-out, partly loaded, and empty. Understanding these proportions will help determine the value of potential weight reduction and cargo volume increasing features. Research should explore products and methods that allow more to be packed into a 53 ft dry van trailer, such as thinner walls, better flooring options, and double decking.
Management of temperature remains a challenge for vehicle and component OEMs. Listed below are areas where thermal management is needed:
- Engine Compartment. Managing the temperature in the engine compartment is important since increased heat has had side effects, some anticipated and some not expected. The impact of heat on major components of the engine itself and on the oil for lubrication is expected and addressed. However the impact on electrical insulation, seals on electronics, air compressors, and air hoses also need to be considered. The effect of waste heat recovery (WHR) or Rankine cycles is being addressed by the SuperTruck program.
- Exhaust. Exhaust temperatures can exceed 1,100°F (600°C), requiring special precautions (CVSA, 2010; Volvo Group North America, Inc., 2009). Insulation and protection must be provided to the pipes from the engine to the aftertreatment system and at the exhaust outlet. Some of this insulation and protection is to maintain the necessary temperature for the chemical reactions in the aftertreatment system, and some is to protect driver and service technician contact. Techniques for mitigating the temperature of the exhaust to protect personnel and materials external to the truck (such as hay under a truck in a field that is being harvested) were devised by several OEMs. Because vertical exhaust stacks create extra weight and aerodynamic drag, these high-temperature exhaust pipes are often designed to be closer to the ground.
- Brakes. Decreases in stopping distance over the last few years have required the brakes to do more work. This was accomplished in some cases by upsizing components of the braking system. Some vehicles have switched to disc brakes, but drum brakes remain the most common option, requiring cooling air flow to remain effective under heavy use, such as when descending mountains. The improvements in aerodynamics have driven reductions in the drag associated with the wheels and the wheel wells. The net effect has been to move the airstream away from the wheels, which can reduce air-cooling to the wheels. The improvements in aerodynamics also require the brakes to assume more of the work for stopping the vehicle.
- Driver Personal Comfort. The driver needs to be kept warm in the winter months and cool in the summer months. Blower motors and electrical resistance heaters (such as for mirrors) can be a measureable drain on the batteries and alternators. Some fleets have moved to using battery-powered air conditioners combined with diesel-fired heaters for comfort when not operating. However, the reliability and performance of the batteries have not always lived up to expectations. The DOE CoolCab and the Shorepower Truck Electrification Project (STEP, see Chapter 6) projects address this need.
- Driver Food. An often overlooked requirement in long-haul applications using sleepers is the need to maintain food in a refrigerator and to provide heating for the food.
- Food Freight. Recently, the Food and Drug Administration published regulations on food safety in trucking. While not as stringent as anticipated, they do highlight the need to control temperatures in refrigerated trailers. Trailer design and fleet operations have advanced to using trailers and box trucks with multiple refrigerated zones. This allows them to keep frozen food at lower temperatures than produce and to maximize the freight efficiency. The DOE STEP project, which is the same as the Interstate Grid Electrification project, ARRA VTO 70, addresses this issue through the transportation refrigeration unit (TRU) components.
- Fuel. The new emphasis on natural gas as a fuel for trucks has created the need for cryogenic temperature control on natural gas-powered trucks and tractors for maintaining liquefied natural gas.
- Batteries. Whether batteries are used for starting the vehicle, hotel loads for the driver, the air conditioning system, a hybrid power train, or a trailer refrigeration unit, thermal management of the battery is extremely important. Some of these issues, at least prototypes and analysis, are being addressed in the SuperTruck program. There is opportunity for more fundamental work to enable solutions to some of the thermal problems for batteries.
- Solar. Solar power has often been talked about for truck and passenger car applications. Generally, it has been perceived as too expensive for too little energy. However, it is now in production on a few passenger cars and is being tested in trucks. The SuperTruck program is addressing some of this. It is mentioned here only because the source of power is thermal in nature.
Projects for Thermal Management
The committee has identified four projects related to thermal management. Only the first project was identified as falling under the purview of the Partnership. Project VSS075, CoolCab Test and Evaluation and CoolCalc HVAC Tool Development, is discussed in Chapter 6 on engine idle reduction. It is mentioned here because the project is looking for ways to control the thermal energy for air-conditioning systems that provide driver comfort. This project at the National Renewable Energy Laboratory (NREL) addresses reducing the heating, ventilation, and air conditioning (HVAC) need as an approach to decreasing fuel use. The project has links with manufacturers and a good view of the end user. Anderson (2014) notes: “The goal is to demonstrate at least a 30% reduction in long-haul truck idle climate control loads with a 3-year or better payback period by 2015.”11 The program
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11 D. Anderson, 2014, “Vehicle and Systems Simulation and Testing,” presentation to the committee, September 3, 2014.
plan is to develop and integrate technologies that address auxiliary load reduction and idle reduction to greatly improve commercial vehicle efficiency. To date, the CoolCalc modeling tool has been released to select industry partners, and testing is under way with instrumented cabs. Accomplishments include quantification of the impact of advanced paints, advanced glazings, sleeper microclimate evaluation, insulation, and auxiliary air-conditioning system. The project started in FY 2011 and is expected to be completed in September 2015. As might be expected, cab color makes a measurable difference in the heat load inside the cabin. The specific measurements will give guidance to manufacturers and fleets for the future selection of colors. Battery sizing will help to reduce the weight of the batteries and provide longer periods of comfort when the driver is off duty. The DOE budget (CoolCab/CoolCalc) is $1,060,000/$615,000, with the contractor’s share $488,000.
Another project, VSS134, Vehicle Thermal System Modeling in Simulink, is focused on providing heat to the driver rather than cooling, but with the same emphasis on reducing fuel use when the driver is off-duty. This project was not included by the Partnership in its list of projects. The committee notes that VSS134 includes Daimler Trucks North America as one of its partners, which leveraged analysis capabilities being developed to assist on the SuperTruck project. The project also leveraged model results for the CoolCab project impact estimation.
Response to Recommendations from the NRC Phase 2 Review
R5-6 NRC Phase 2 Recommendation 5-6. Thermal Management: The Partnership should continue priority support of nano-fluid and high-efficiency under-hood cooling systems, as well as review other potential technical concepts, and validate them as an integrated system.
21CTP Response: DOE is planning to expand R&D on high efficiency HVAC systems. DOE agrees and is continuing support of nano-fluid and high-efficiency under-hood cooling systems. DOE will monitor other potential technology solutions to reach thermal management objectives.
Committee Comment on Response to 5-6
The Partnership indicates DOE is continuing to support R&D on nanofluids and underhood cooling systems. The Partnership also indicates DOE is planning to expand efforts for high-efficiency HVAC. No specifics were provided. The Daimler Trucks North America SuperTruck effort did include high-voltage HVAC developments.
Finding and Recommendation
Finding 5-8. The current research in thermal management is limited and more focused on idle reduction. The area of thermal management is in fact broader and encompasses a variety of areas applicable to medium- and heavy-duty vehicles.
Recommendation 5-7. The 21st Century Truck Partnership should establish a goal to reduce the energy required over a drive cycle for non-engine thermal loads by 50 percent and establish a research program focused on cooling for natural gas, trailer refrigeration, and batteries. The goal to increase heat load rejected by thermal management systems by 20 percent without increasing radiator size should continue to be pursued.
The only focus on driveline power is to comment on the Partnership’s response to an NRC Phase 2 recommendation.
R5-7 NRC Phase 2 Recommendation 5-7. Driveline Power Demand: The term “powertrain” should be removed from the 21 CTP Goal 5.b statement. In addition, the Partnership should update its study on the driveline power demand of 12 hp.
21CTP Response: The Partnership concurs: a subsequent revision to the Partnership’s goal wording made after the completion of this review has removed the word “powertrain” from the subject goal, which will be published as part of the final white paper/roadmap document. The Partnership will review the current information on driveline power demand and consider updates to this study. The Partnership will review research results from the SuperTruck teams to gather current technology information for power demand, and revise assessments of power demand as appropriate.
Committee Comment on Response to 5-7
The term “powertrain” has been removed from the vehicle power demand goals in the 21CTP roadmap and technical white papers, Section 3 (2013), but not from the document’s executive summary. The current goals for the Partnership are not specific in the driveline area.
As part of the effort for friction and wear, the project Development of a High Power Density Driveline, VSS058, was identified.12 This project at Argonne National Laboratory (ANL) targets weight reduction through reduction in size and weight of the driveline systems. Driveline size reduction is to be achieved by developing coatings and lubricants for increasing the power density of the systems. The expectation is that these improvements would enable the design of smaller and lighter weight components without loss of performance. Good progress has been made in the development of a low viscosity lubricant formulation. Other work explored scuffing mechanisms and contact fatigue performance evaluation. None of the heavy-duty
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12 Ibid.
transmission manufacturers are involved in the work. The project started in October 2010 and is expected to end in FY 2015. The DOE funding is $870,000 and the contractor share is $120,000.
Most vehicle-level energy-balance studies indicate the driveline is about 98 percent efficient in transmitting energy from the engine to the wheels. Recent studies by Southwest Research Institute (SwRI) for line-haul applications indicate weight reduction may not be a good area for achieving improvements in fuel consumption even though it can result in load specific fuel reductions in fuel consumption as measured in gallons per ton-mile. Therefore, the proposed project’s objective of a 5-7 percent improvement in fuel savings from lubrication and size/weight reduction of the driveline is not likely to be achieved. The connection between the lubricant and a 25 percent reduction in the size of driveline components is not clear.
The second project presented was Parasitic Engine Friction Collaboration, VSS005. This work deals with lubrication of the engine and should rightfully be classified with engine development for improved brake thermal efficiency (BTE). It should not be counted as vehicle power demand research. This project at ANL began in FY 2010 and is scheduled to be complete at the end of FY 2015, with a total budget of $1,887,000 for the 6 years. In this project, advanced engine friction models are applied to predict where parasitic friction losses occur and how advanced tribological concepts (lubricants, materials, additives, engineered surfaces) can reduce losses, component by component. By doing so, the project identifies potential pathways to reduce losses and thus improve both fuel consumption and reliability and durability.
Current government-sponsored research is focused on lubrication to achieve reductions in friction, primarily in the engine, with some work on the driveline. No work is perceived to be looking at friction and lubrication of power steering pumps, water pumps, air compressors, wheel ends, clutches, or gears. The industry is actively pursuing improvements in these areas and claiming as much as 2 percent improvement in fuel consumption.
OVERALL COMMENTS, FINDINGS, AND RECOMMENDATIONS
Before closing this chapter, there are few comments that apply to the general area of vehicle power demands and not necessarily to any of the individual areas that have been addressed in this chapter.
The Partnership also identified project VSS119, Fleet DNA, as under the umbrella of 21CTP. This project is led by NREL with many industry (NTEA/GTA, Cummins, PG&E, Oshkosh, Waste Management, Zonar, Parker), academic (Ohio State University, California State University, North Carolina State University, Calstart), and government/regulatory (ORNL, Clean Cities, South Coast Air Quality Management District [SCAQMD], CARB, EPA, ANL, City of Indianapolis) collaborations. The goal of this project is to define data capture and structure for a variety of drive cycles and conditions, and to then create a data storage warehouse to make this data available to a broad community of users. The project has also included an effort to incorporate models and data analysis tools. Highest priority has been given to Class 2 and Class 8 vehicle, and the current data have been gathered mostly from delivery vans and Class 8 trucks. Capturing such real-world data and drive cycles is extremely important to identifying areas of opportunity for reducing fuel consumption.
Response to Recommendations from the NRC Phase 2 Review
There was an NRC Phase 2 recommendation that applied broadly to the vehicle power demands area. The response to it by the Partnership and the committee’s comment are noted as follows:
NRC Phase 2 Recommendation 5-8. Although it is tempting to assume that the SuperTruck projects will address all of the technologies required to reduce tractor-trailer fuel consumption, in practice many technologies may be left behind, particularly those that are not yet very mature. The Partnership should carefully review the technologies that have been identified and determine whether any technologies to reduce vehicle power demand are not being adequately addressed by the SuperTruck program. The DOE should define projects and find funding to support the development of technologies beyond the scope of SuperTruck.
21CTP Response: The SuperTruck projects are designed to develop combinations of advanced technologies into a Class 8 platform that can be commercialized in the near-term. In order to ensure commercial viability, the technologies are chosen by each industry team and not dictated by DOE. Technical approaches for reducing petroleum consumption that are not addressed by the SuperTruck projects may be appropriate for investigation through other pathways that address longer term technology development. Follow-on activities being considered post-SuperTruck may be used to address these technologies.
Committee Comment on Response to 5-8
The Partnership’s response indicates limited acceptance of this recommendation but provides no specific suggestions for additional research. Now that the technology choices of the SuperTruck teams are available, the Partnership should review the situation and determine which technologies require new or additional R&D.
Finding 5-9. The industry has seen significant changes and improvements in fuel consumption since the Partnership was formed in 2002. As improvements in aerodynamic drag and tire rolling resistance have been made, the relative importance of accessory and auxiliary loads has increased.
The Partnership has repeatedly revised its goals to reflect the improvements and any changes in regulations.
Recommendation 5-8. The Partnership, in setting its goals, should use drive cycles, as it did for the SuperTruck progam. The cycles should take into account the many drive cycles that already exist, current operational regulations of the Federal Motor Carrier Safety Administration, the current and future regulations of EPA/NHTSA, and real world data that are being accumulated by such projects as the National Renewable Energy Laboratory’s Fleet DNA project. Data on real-world weights of vehicles needs to be included.
Recommendation 5-9. Fleets either measure or monitor miles per gallon or gallons of fuel consumed. They rarely monitor load specific fuel consumption (LSFC) in gallons per 1,000 ton-mile, as in the regulations. Work is needed to change this practice. The Partnership, as part of DOE, should take the lead role, in combination with EPA, NHTSA, and CARB, in creating demand, perhaps through some sort of incentive, to produce LSFC information.
21CTP (21st Century Truck Partnership). 2013. Roadmap and Technical White Papers. U.S. Department of Energy Office of Energy Efficiency and Renewable Energy. https://www1.eere.energy.gov/vehiclesandfuels/pdfs/program/21ctp_roadmap_white_papers_2013.pdf.
Ajayi, O.O., C. Lorenzo-Martin, A.C. Greco, and G.R. Fenske. 2014. Development of High Power Density Driveline for Vehicles (Developing Enabling Tribological Technologies). Argonne National Laboratory. DOE Annual Merit Review VSS058, Washington, D.C., June 19.
APS (American Physical Society). 2015. Energy Units. American Physical Society. Accessed March 10, 2015. http://www.aps.org/policy/reports/popa-reports/energy/units.cfm.
ATRI (American Trucking Research Institute). 2013a. An Analysis of the Operational Costs of Trucking: A 2013 Update. Arlington, Va.: American Trucking Research Institute.
ATRI. 2013b. Freight Performance Measures Analysis of Freight-Significant Highway Locations–2013. Arlington, Va.: American Trucking Research Institute.
Benedict, R. 2014. A System for Automatically Maintaining Pressure in a Commercial Truck Tire. The Goodyear Tire & Rubber Company. DOE Annual Merit Review VSS085, Washington, D.C., June 19.
Birky, A.K. 2014. Modeling for Market Analysis: HTEB, TRUCK, and LVChoice. TA Engineering, Inc. DOE Annual Merit Review VAN012, Washington, D.C., June 18.
Cox, J. 2014. Plug-in Hybrid Electric Commercial Fleet Demonstration and Evaluation. Principal Investigator: Matt Miyasato, South Coast Air Quality Management District. DOE Annual Merit Review VSS083, Washington, D.C., June 19.
CVSA (Commercial Vehicle Safety Alliance). 2010. Inspection of Vehicles Equipped with 2007 and 2010 EPA Certified Engines. North American Standard Inspection Program. Accessed March 11, 2015. http://goo.gl/OhYubo.
Delgado, O., and N. Lutsey. 2014. The U.S. SuperTruck Program: Expediting Development of Advanced HDV Efficiency Technologies. Washington, D.C.: International Council on Clean Transportation (ICCT). http://www.theicct.org/us-supertruck-program-expediting-developmentadvanced-hdv-efficiency-technologies. Accessed April 23, 2015.
Deter, D. 2014. Cummins MD & HD Accessory Hybridization CRADA. Center for Transportation Analysis and ORNL. DOE Annual Merit Review VSS133, Washington, D.C., June 16-20.
DOE (U.S. Department of Energy). 2014. Lightweight Materials R&D Program, FY 2013 Annual Progress Report. Vehicle Technologies Office. DOE/EE-1039. http://energy.gov/sites/prod/files/2014/04/f15/2013_lightweight_materials_apr.pdf. Accessed August 19, 2015.
EPA (U.S. Environmental Protection Agency). 2014. EPA-designated “SmartWay Elite” Trailers. EPA SmartWay Technology Program. http://epa.gov/smartway/forpartners/documents/aerodynamic/420f15008.pdf. Accessed March 10, 2015.
Erb, A. 2015. The Place of Low Rolling Resistance Tires in EPA’s Greenhouse Gas Reduction Strategy. U.S. Environmental Protection Agency. 2015 SAE Government/Industry Meeting, Washington, D.C., January 23. http://www.sae.org/events/pdf/gim/2015_gim_guide.pdf.
Fadler, G. 2013. Navistar Fuel Economy and Emissions. Navistar, Inc. Presentation to the NRC Committee on Assessment of Technologies and Approaches for Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles, Phase 2, Washington, D.C.
Fenske, G., A. Matthews, and N. Demas. 2014. DOE/DOD Parasitic Energy Loss Collaboration. Argonne National Laboratory. DOE Annual Merit Review VSS005, Washington, D.C., June 16.
FHWA (Federal Highway Administration). 2005. Freight Performance Measurement: Travel Time in Freight-Significant Corridors. U.S. Department of Transportation. http://www.ops.fhwa.dot.gov/freight/freight_analysis/perform_meas/fpmtraveltime/traveltimebrochure.pdf.
Gonder, J. 2014. ICEER: Internal Combustion Engine Energy Retention. National Renewable Energy Laboratory Team: E. Wood and S. Lopp. DOE Annual Merit Review VSS126, Washington, D.C., June 18.
Heavy Duty Manufacturers Association. 2014. Transformative Technology for Tractor Driver Behavior. Heavy Duty Manufacturers Association Commercial Vehicle Outlook Conference, Dallas, Tex., August 20.
Kambiz, S. 2014. DOE’s Effort to Improve Heavy Vehicle Fuel Efficiency through Improved Aerodynamics. Lawrence Livermore National Laboratory. DOE Annual Merit Review VSS006, Livermore, Calif., June 19.
Karbowski, D., A. Rousseau, S. Pagerit, N. Kim, and D. Lee. 2014. Trip Prediction and Route-Based Vehicle Energy Management. Argonne National Laboratory. DOE Annual Merit Review VSS125, Washington, D.C., June 18.
Kim, N., and A. Rousseau. 2014. Vehicle Level Model and Control Development and Validation Under Various Thermal Conditions. Argonne National Laboratory. DOE Annual Merit Review VSS127, Washington, D.C., March.
Lustbader, J. 2014. CoolCab Test and Evaluation & CoolCalc HVAC Tool Development. National Renewable Energy Laboratory Team: C. Kreutzer, M. Jeffers, J. Tomerlin, R. Langewisch and K. Kincade. DOE Annual Merit Review VSS075, Washington, D.C., June 19.
Lustbader, J., and T. Kiss. 2014. Vehicle Thermal System Modeling in Simulink. National Renewable Energy Laboratory. DOE Annual Merit Review VSS134, Washington, D.C., June 16.
Martin, J., M. Bowman, and P. Votruba-Drzal. 2014. A Materials Approach to Fuel-Efficient Tires. PPG Industries. U.S. Department of Energy Annual Merit Review VSS084, Washington, D.C., June 19.
Meyer, J. 2014. Advanced Climate Systems for EV Extended Range (ACS forEVER). Halla Visteon Climate Control Corp., Presenter: J. Schneider. DOE Annual Merit Review VSS135, Washington, D.C., June 19.
NACFE (North American Council for Freight Efficiency). 2013. Tire Pressure Systems—Confidence Report. http://nacfe.org/wp-content/uploads/2014/01/TPS-Detailed-Confidence-Report1.pdf. Accessed April 24, 2015.
NRC (National Research Council). 2010. Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles. Washington, D.C.: The National Academies Press.
NRC. 2012. Review of the 21st Century Truck Partnership, Second Report. Washington, D.C.: The National Academies Press.
NRC. 2014. Reducing the Fuel Consumption and Greenhouse Gas Emissions of Medium- and Heavy-Duty Vehicles, Phase Two: First Report. Washington, D.C.: The National Academies Press.
Pearl, I. 2014. Natural Gas Vehicles in Hazard Classification Areas. Natural Gas Vehicles Task Force Meeting. http://www1.eere.energy.gov/cleancities/pdfs/ngvtf14_pearl.pdf. Accessed April 4, 2015.
Quinley, R. 2010. WIM Data Analyst’s Manual, FHWA Report IF-10-018, June 2018. http://www.fhwa.dot.gov/pavement/wim/pubs/if10018/if10018.pdf.
Rask, E. 2014. Advanced Technology Vehicle Lab Benchmarking-Level 2 (in-depth). Argonne National Laboratory. DOE Annual Merit Review VSS031, Washington, D.C., June 17.
Rugh, J.P. 2014. Electric Drive Vehicle Climate Control Load Reduction. National Renewable Energy Laboratory. DOE Annual Merit Review VSS097, Washington, D.C., June 17.
Smith, M. 2014. Aerodynamic Lightweight Cab Structure Components. Pacific Northwest National Laboratory. DOE Annual Merit Review LM060, Washington, D.C., June.
Stephens, T. 2014. Impact Analysis: VTO Baseline and Scenario (BaSce) Activities. Argonne National Laboratory. DOE Annual Merit Review VAN001, Washington, D.C., June 18.
Technology and Maintenance Council. 2014. Fuel Efficiency and Vehicle Emissions Regulations: Now and for the Foreseeable Future. S11 Tech Session, March 11. http://www.tech-i-m.com/insights/. Accessed March 27, 2015.
Volvo Group North America, Inc. 2009. Volvo’s SCR No Regen Engine. http://www.volvotrucks.com/SiteCollectionDocuments/VTNA_Tree/ILF/Products/2010/09-VTM075_NoRegen_SS_041609.pdf. Accessed March 11, 2015.
Walkowicz, K. 2014a. Medium Duty ARRA Data Reporting and Analysis. National Renewable Energy Laboratory Team: A. Duran and A. Ragatz. DOE Annual Merit Review VSS124, Washington, D.C., June 17.
Walkowicz, K. 2014b. Fleet DNA. National Renewable Energy Laboratory Presenter: A. Duran. DOE Annual Merit Review VSS119, Washington, D.C., June 16.
Waltzer, S. 2014. U.S. EPA SmartWay Technology Program. Presentation to the Technology and Maintenance Council, Portland, OR, March 11.
Woodrooffe, J., and T. Vachon. 2000. Revision 3 Typical Large Truck-Tractor Trailer: Distribution of Energy Requirements (kWh) 65 mph, Two load conditions, Level Road for one hour.
Regulations Related to Certification of Engines for Discussion of Accessory versus Auxiliary Loads
§1065.110 Work inputs and outputs, accessory work, and operator demand.13
(a) Work. Use good engineering judgment to simulate all engine work inputs and outputs as they typically would operate in use. Account for work inputs and outputs during an emission test by measuring them; or, if they are small, you may show by engineering analysis that disregarding them does not affect your ability to determine the net work output by more than ±0.5% of the net expected work output over the test interval. Use equipment to simulate the specific types of work, as follows:
(1) Shaft work. Use an engine dynamometer that is able to meet the cycle-validation criteria in §1065.514 over each applicable duty cycle.
(i) You may use eddy-current and water-brake dynamometers for any testing that does not involve engine motoring, which is identified by negative torque commands in a reference duty cycle. See the standard setting part for reference duty cycles that are applicable to your engine.
(ii) You may use alternating-current or direct-current motoring dynamometers for any type of testing.
(iii) You may use one or more dynamometers.
(iv) You may use any device that is already installed on a vehicle, equipment, or vessel to absorb work from the engine›s output shaft(s). Examples of these types of devices include a vessel›s propeller and a locomotive›s generator.
(2) Electrical work. Use one or more of the following to simulate electrical work:
(i) Use storage batteries or capacitors that are of the type and capacity installed in use.
(ii) Use motors, generators, and alternators that are of the type and capacity installed in use.
(iii) Use a resistor load bank to simulate electrical loads.
(3) Pump, compressor, and turbine work. Use pumps, compressors, and turbines that are of the type and capacity installed in use. Use working fluids that are of the same type and thermodynamic state as normal in-use operation.
(b) Laboratory work inputs. You may supply any laboratory inputs of work to the engine. For example, you may supply electrical work to the engine to operate a fuel system, and as another example you may supply compressor work to the engine to actuate pneumatic valves. We may ask you to show by engineering analysis your accounting of laboratory work inputs to meet the criterion in paragraph (a) of this section.
(c) Engine accessories. You must either install or account for the work of engine accessories required to fuel, lubricate, or heat the engine, circulate coolant to the engine, or to operate aftertreatment devices. Operate the engine with these accessories installed or accounted for during all
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13 See 70 FR 40516, July 13, 2005, “Engine-Testing Procedures”, as amended at 73 FR 37292, June 30, 2008. e-CFR data current as of April 22, 2015. Available at http://www.ecfr.gov/cgi-bin/text-idx?SID=28840d4abb0e4aa4074d081c70105ee5&node=se40.33.1065_1110&rgn=div8.
testing operations, including mapping. If these accessories are not powered by the engine during a test, account for the work required to perform these functions from the total work used in brake-specific emission calculations. For air-cooled engines only, subtract externally powered fan work from total work. We may ask you to show by engineering analysis your accounting of engine accessories to meet the criterion in paragraph (a) of this section.
(d) Engine starter. You may install a production-type starter.
(e) Operator demand for shaft work. Operator demand is defined in §1065.1001. Command the operator demand and the dynamometer(s) to follow a prescribed duty cycle with set points for engine speed and torque as specified in §1065.512. Refer to the standard-setting part to determine the specifications for your duty cycle(s). Use a mechanical or electronic input to control operator demand such that the engine is able to meet the validation criteria in §1065.514 over each applicable duty cycle. Record feedback values for engine speed and torque as specified in §1065.512. Using good engineering judgment, you may improve control of operator demand by altering on-engine speed and torque controls. However, if these changes result in unrepresentative testing, you must notify us and recommend other test procedures under §1065.10(c)(1). (f) Other engine inputs. If your electronic control module requires specific input signals that are not available during dynamometer testing, such as vehicle speed or transmission signals, you may simulate the signals using good engineering judgment. Keep records that describe what signals you simulate and explain why these signals are necessary.
