This chapter provides an overview and the committee’s evaluation of the SuperTruck projects that began in 2010. The SuperTruck projects were designed to provide complete long-haul Class 8 trucks that incorporate a wide range of technologies that have been developed under the 21st Century Truck Partnership (21CTP) over the past decade. This program offers the opportunity to demonstrate which technologies can actually be implemented in a truck, as well as the opportunity to perform vehicle-level testing of the technologies. The chapter introduction describes the basic design and intent of the SuperTruck projects. The second section describes the goals, timetables, tasks, and deliverables of the SuperTruck projects. The third section examines in detail the budgets available for these projects, and the fourth section looks at the SuperTruck project teams and the technologies that they plan to evaluate. The chapter concludes with the committee’s evaluation of the SuperTruck project plans, goals, and overall approach.
Nature of the SuperTruck Projects
On January 11, 2010, the Department of Energy (DOE) announced the selection of nine projects, totaling more than $187 million, to improve the fuel efficiency of heavy-duty trucks and passenger vehicles. The funding includes more than $100 million from the American Recovery and Reinvestment Act of 2009 (ARRA).1 The projects require that private industry contribute at least 50 percent of the project cost, and so a total of more than $375 million will be provided for research, development, and demonstration projects (DOE, 2010a).
Of the funding recipients announced by DOE, three projects will focus on measures to improve the overall efficiency of long-haul Class 8 trucks. These projects will receive $115 million in DOE funding to develop and demonstrate full-vehicle system-level technologies by 2015. The total cost of the full-vehicle projects will be more than $230 million, including contractor contributions to the funding. Three projects have been selected for awards under the SuperTruck program:2
1. Cummins, Inc., Columbus, Indiana—Develop and demonstrate a highly efficient and clean diesel engine, an advanced Waste Heat Recovery (WHR) system, an aerodynamic Peterbilt tractor-trailer combination, and a solid oxide fuel cell auxiliary power unit (APU) to reduce engine idling.
2. Daimler Trucks North America, LLC, Portland, Oregon—Develop and demonstrate technologies including optimized combustion, engine downsizing, electrification of auxiliary systems such as oil and water pumps, waste heat recovery, improved aerodynamics, hybridization, and possibly a fuel cell auxiliary power unit to reduce engine idling.
3. Navistar, Inc., Melrose Park, Illinois—Develop and demonstrate technologies to improve truck and trailer aerodynamics, combustion efficiency, waste heat recovery, hybridization, idle reduction, and reduced rolling resistance tires.
The objective of the three SuperTruck projects is to develop and apply technologies leading to a system-level demonstration of highly efficient and clean diesel-powered Class 8 trucks that (DOE, 2010b):
• Achieve a 50 percent increase in vehicle freight efficiency measured in ton-miles per gallon, which
1 Funding Opportunity Announcement (DOE, 2010b, pp. 6-8).
2 Volvo Technology of America was awarded a fourth SuperTruck project in August 2011. Details of the technology development plan were not available to the committee during the preparation of this report.
translates to a 33 percent reduction in load-specific fuel consumption (gallons per 1,000 ton-miles);
• Achieve at least a 20 percent improvement through engine efficiency development, and achieve 50 percent brake thermal efficiency (BTE) under highway cruise conditions, which translates to a 16.7 percent reduction in fuel consumption due to engine improvements; and
• Evaluate potential approaches to 55 percent BTE in an engine via modeling, analysis, and potentially also laboratory tests.
Deliverables include computer simulation and hardware testing, as well as full-vehicle demonstrations using realistic drive cycles. An additional deliverable called for in the Funding Opportunity Announcement (FOA) is that “the systems developed shall be validated as cost effective via a business case analysis and will be reviewed for commercialization potential in later project phases as part of the phase gate review process” (DOE, 2010b, p. 7).
Each of the three teams is composed of a number of partners, including engine and truck original equipment manufacturers (OEMs), suppliers, fleet owners, universities, and DOE laboratories. Although each team has the same objectives, different technologies have been selected by the different teams to meet these objectives. For example, Navistar and Daimler plan to use hybridization in their approach to meeting the 50 percent vehicle freight efficiency target, whereas Cummins does not. In addition, the Navistar and Daimler teams plan to use different types of hybrid systems. Later in this section, the teams and the technical approach used by each team are identified. In general, each team will seek to improve vehicle freight efficiency through improved powertrain efficiency, idle reduction, reduced aerodynamic drag, and reduced tire rolling resistance, among other technologies.
Background and Relationship to Previous 21st Century Truck Projects
The SuperTruck projects can be considered a logical extension of prior research and development (R&D) activities of the 21CTP, in the sense that many of the technologies that will be applied in a system-level demonstration began as R&D initiatives and component-level demonstrations. Indeed, the National Research Council’s (NRC’s) Phase 1 report on the 21CTP had several recommendations for system-level demonstrations and a recommendation that industry partners assess cost objectives required to achieve commercial viability (NRC, 2008). The SuperTruck projects should result in more accurate estimates of the commercial viability of the various technologies. In Table 3-9 of the NRC (2008) Phase 1 report, it is noted that a shortcoming of component testing is that such hardware demonstrations are not subject to the realistic packaging constraints typical of commercialization. Prototype vehicle demonstrations should address this concern. Cummins intends to demonstrate 50 percent BTE under highway cruise conditions,3 as requested in the program objectives and as recommended by the NRC Phase 1 report. The other teams are expected to provide similar demonstrations. Recommendation 4-6 in the NRC Phase 1 report suggests continued development and demonstration of heavy-duty hybrid truck technology, as will be addressed by the Navistar and possibly also by the Daimler SuperTruck teams. The SuperTruck projects plan to address Recommendation 5-1 of the NRC Phase 1 report, which suggests continued evaluation of systems that can improve idle reduction, along with the study of the cost-effectiveness of such systems. The Cummins and Daimler teams plan to evaluate fuel cell APUs, and the Navistar team plans to use the hybrid system battery to provide idle reduction. With regard to lightweight materials research, the NRC Phase 1 report’s Recommendation 5-3 notes that it should be the responsibility of truck manufacturers to take the next steps of system integration, product validation, and production of a lightweight truck—an opportunity afforded by the SuperTruck program. Many of the fuel-saving technologies that will be implemented by the SuperTruck teams add significant weight to the vehicle, so all the teams have plans to implement offsetting weight reductions. In short, the SuperTruck program appears to address several of the shortcomings noted in the NRC (2008) Phase 1 report.
The project goals were listed by DOE (2010b) in the Funding Opportunity Announcement (FOA). The overall goal for Class 8 tractor-trailers is to develop and demonstrate a 50 percent total increase in vehicle freight efficiency measured in ton-miles per gallon (equivalent to a 33 percent load-specific fuel consumption reduction [gal/1,000 ton-mile]). This will be achieved through efficiency improvement in advanced vehicle systems technologies and advanced engine technologies. The project duration will be up to 5 years. At least 20 percent of this 50 percent improvement will be through the development of a heavy-duty diesel engine capable of achieving 50 percent BTE on a dynamometer under a load representative of a level road at 65 mph (see Chapter 3 in this report). Specific technology developments mentioned in the FOA include ancillary systems, waste heat recovery, materials, and electrification in addition to advanced combustion techniques.
The project efficiency goals must be met while adhering to prevailing (Environmental Protection Agency [EPA]) 2010
3 Donald Stanton, Cummins, “Cummins-Peterbilt SuperTruck Program,” presentation to the committee, September 8, 2010, Washington, D.C.
emissions standards as well as the vehicle safety and regulatory requirements that apply to Class 8 tractor-trailers. The FOA stipulates that the vehicle efficiency improvement will require an integrated team that includes an engine manufacturer, a truck OEM, and a trailer manufacturer, along with suppliers, national laboratories, universities, fleet operators, and other stakeholders, to ensure maximum benefit.
Additional fuel-saving technologies listed in the FOA include electrical or mechanical drivetrain hybridization with energy storage and regeneration, along with reductions in aerodynamic drag, rolling resistance, weight, and main engine idle. The FOA specifies that any demonstration of achievement must utilize a test cycle proposed by the team that is representative of a typical long-haul Class 8 truck, and including a minimum of 75 percent of the distance traveled under highway conditions, with a vehicle weight of 65,000 lb. The level of improvement is based on a comparison to a similarly configured “best-in-class” 2009 commercially available Class 8 vehicle. Comparable vehicle performance, such as acceleration times and grade capability, is to be maintained by the SuperTruck vehicle.
A second project goal is to identify key pathways to achieving a 55 percent BTE heavy-duty diesel engine, through modeling and analysis conducted in parallel with work toward the overall goal of a 50 percent improvement in vehicle freight efficiency. Critical components and/or systems needing specific additional development to achieve this 55 percent BTE goal should also be identified. This engine must be capable of meeting 2010 emissions standards, and it must be commercially viable, which implies a requirement for cost-effectiveness.
Relationship Between SuperTruck Goals and Previous (2006) 21CTP Goals
The most outstanding difference between the SuperTruck goals given above and the 21CTP goals established in 2006 is that the 2006 goals included no requirement for a vehicle measurement of efficiency improvement. This omission in the 2006 goals was noted in the NRC Phase 1 report in Overall Report Recommendation 1-1, stating in part: “more (major truck) manufacturers should be participants” and goals should be “strategic to reducing fuel consumption of heavy-duty vehicles” (NRC, 2008, p. 2). These omissions have been corrected in the current project goals, which require a vehicle demonstration of fuel-consumption reduction. It is particularly refreshing that the SuperTruck demonstration is required to be conducted under real-world operation and gross vehicle weight (GVW) conditions.
Although the 2006 21CTP goal provided for achieving a 20 percent increase in (peak) BTE to 50 percent, the 2008 NRC Phase 1 report, in Recommendation 3-1, clarified that “objective and consistent criteria (were not) used to assess the success or failure of achieving that key goal” (NRC, 2008, p. 3). This shortcoming has been corrected in the current project goals, in which an engine dynamometer demonstration is required over a simulated real-world duty cycle, and the 50 percent BTE goal is to be achieved at the “highway cruise” condition.
It is worth noting that the target for 50 percent BTE under “highway cruise” conditions is significantly more stringent than the original 21CTP goal of 50 percent peak BTE. The original goal was for the engine’s best operating point, which is typically at or near full load at relatively low engine speed. Cruise speed is typically somewhat higher than the best BTE speed, and cruise load is lower than the typical best BTE load point. In addition, the vehicle aerodynamic and rolling resistance goals of SuperTruck will lead to lower vehicle power demand on the engine at cruise, which makes the target of 50 percent BTE at cruise even more challenging. The SuperTruck contractors may find that this change in goals introduces a significant technical challenge.
The 2006 21CTP goals provided for an effort to develop component technologies for reaching a 55 percent (peak) BTE, with a particular focus on low-temperature combustion (LTC) (NRC, 2008). The current project reduces the 55 percent BTE focus to one providing for modeling and analysis, including a requirement to comply with 2010 criteria emissions. The FOA calls for identifying critical components and/or systems needing specific development, and finally evaluating the overall system for commercial viability. No test demonstration appears to be required, although two SuperTruck teams (Cummins and Navistar) showed the committee plans for a test cell demonstration of the 55 percent target.
In summary, comparing the goals for these SuperTruck projects to the previous (2006) 21CTP goals, it appears that the DOE has implemented more robust requirements for demonstrations under near-real-world conditions and has required the contracting teams to include a wide range of technical specialties. Now that a number of technologies have been demonstrated on a laboratory scale under previous 21CTP projects, this new approach should serve the trucking industry and the public more favorably over the next several years.
4 Patrick Davis, DOE, “U.S. Department of Energy Vehicle Technologies Program Overview,” presentation to the committee, September 8, 2010, Washington, D.C.
5 Volvo Technology of America was awarded $19 million in SuperTruck funding in August 2011. Volvo Technology of Sweden was awarded a similar amount by the Swedish government under a separate contract. The two contracts will combine to provide a SuperTruck program similar in scope to the other three contracts.
• Cummins team: $38,831,115;
• Daimler team: $39,559,868; and
• Navistar team: $37,328,933.
According to the aforementioned FOA (DOE, 2010b), a 50 percent or greater cost sharing is required of the project teams, but in many cases the requirement for a 50 percent cost sharing will be exceeded. For example, Navistar noted that it was providing $34 million of “in kind funding,” and its partners will provide $16.6 million. When combined with the $37.3 from the DOE, the total Navistar project funding is about $88 million over a 5-year span. It should also be noted that while the Cummins and Daimler teams are directly supported by ARRA funds, the Navistar team is funded from internal DOE resources. This resulted in a delayed start for the Navistar team and will also necessitate annual funding of the contract as DOE funds permit.
In addition to the funding provided for the SuperTruck program directly, there are also projects in the 21CTP budget request that provide support at the component and subsystem level for many of the technologies that will be applied in the SuperTruck projects. Table 1-2 in Chapter 1 shows details of funding for non-SuperTruck-related 21CTP projects. However, that table also includes funding for one of the three SuperTruck projects, namely Navistar, which was $4.35 million in FY 2010 and $7.3 million in FY 2011, and so these amounts would have to be subtracted to arrive at the non-SuperTruck funding level. There is no clear definition in Table 1-2 of which line items are SuperTruck-related and which are not. These non-SuperTruck projects are in areas of technology that are also being explored by the SuperTruck teams, so the effort in the non-SuperTruck projects should complement the SuperTruck project efforts and help fill the technology pipeline for the SuperTruck projects. The SuperTruck projects funding of $115 million is over 5 years, or an average of $23 million per year.
In summary, the DOE has made a significant investment in this effort to improve the overall fuel efficiency of heavy-duty trucks. The SuperTruck projects will form the backbone of the 21CTP work over the next several years, and they will consume most of the budget.
Summarizing the Three SuperTruck Team Plans
In addition to describing the two high-level goals, the DOE in its FOA document (DOE, 2010b) also suggested numerous subtopics that the teams might evaluate for contribution to those goals. The committee finds the topic list substantially inclusive. Each of the three SuperTruck teams made a presentation to the committee providing an overview of its development plans and identifying its team partners, to the extent they were firmed up. Further, both Cummins and Daimler have made presentations at the DEER 2010 (Directions in Energy-Efficiency and Emissions Research) conference, where some additional details of their SuperTruck plans were revealed.
A summary of the three SuperTruck Team plans is shown in Table 8-1. The first column lists technologies that the teams plan to evaluate. This list includes technologies suggested by the DOE, as well as suggestions from the contracting companies. For example, all three companies added optimization opportunities for catalytic exhaust systems that may provide measurable fuel-consumption reductions. Entries described as “(Implied)” indicate that the companies had listed the topic but without any elaboration to describe the approach that they intend to take. It is not clear whether the “implied” technologies will be included in the final project, or what form the technologies might take. Two of the teams made confidential presentations to the committee regarding their plans, including details that were not publicly disclosed. Technologies and approaches that were described only in these confidential presentations are not shown in Table 8-1.
A review of Table 8-1 shows that the three studies will take different approaches to the program goals, although there is overlap. Many of the technology topics are sufficiently broad so as to provide considerable leeway for unique paths and multiple solutions within a specific technology field.
The program targets specify a 50 percent increase in vehicle freight efficiency (ton-miles per gallon) and specify that 20 percent of the improvement must come from improved engine efficiency in terms of BTE. Because fuel economy works in a multiplicative rather than an additive fashion, a 20 percent improvement in engine efficiency combines with a 20 percent reduction in vehicle power demand to produce the required 50 percent overall fuel economy target.6 Items 1 through 6, as well as 8 and 9 in Table 8-1 would directly contribute to reduced load on the engine. The SuperTruck teams have not predicted efficiency performance values for any of these technologies in their public materials.
In vehicle aerodynamics, with the exception of Navistar, it is not clear which technologies are being developed beyond those found in the 2010 NRC report on medium- and heavy-duty vehicle fuel consumption reduction (NRC, 2010). Navistar has identified both an “active fifth wheel”
6 A 20 percent increase in BTE leads to a 20 percent increase in fuel economy, and a 16.7 percent decrease in fuel consumption. A 20 percent reduction in vehicle power demand yields a 20 percent reduction in fuel consumption (assuming constant BTE), and a 25 percent increase in fuel economy. These two improvements combine as follows to meet the 50 percent FE (or 33 percent FC) target:
New Fuel Economy = Old FE × ((1 + % increase in FE from BTE) × (1 + % increase in FE from Reduction in Load)).
New FE = Old FE × ((1 + 20%) × (1 + 25%)) = Old FE × (1.2 × 1.25) = 1.5 × Old FE.
Thus, New Fuel Economy is 50 percent improved, as a result of improving BTE by 20 percent and reducing vehicle power demand by 20 percent.
|Item No.||Technologies That the Teams Plan to Evaluatea||Industry/Government Lab/Academic/Trucking Fleet Teams|
|Engine mfg.: Cummins||Engine mfg.: Detroit Dieselc||Engine mfg.: Navistar|
|Truck OEM: Peterbilt||Truck OEM: Freightliner (Daimler Trucks)||Truck OEM: Navistar|
|Trailer mfg.: Utility||Others TBD||Trailer mfg.: Wabash Suppliers: ATDynamics, Alcoa, Behr, Bosch, Federal Mogul, Michelin, ArvinMeritor. National labs and universities: TPI /LLNL, ANL|
|Suppliers: Eaton, Delphi, Modine, Dana, Bridgestone, Van Dyne||Truck operators: Safeway, Swiftd|
|National labs and universities: ORNL, Purdue|
|Truck operator: U.S. Expressb|
|1||Vehicle aerodynamics||SmartWay tractor, trailer gap closure, full trailer skirts, aft body plates, optimized cooling to reduce aerodynamic impact, other features TBDe||Smartway tractor and trailer, other technologies implied||SmartWay+ tractor, trailer gap device, full trailer skirts, aft body plates, active fifth wheel, height lowered at highway speed|
|2||Transmission||Advanced||(Implied)||See Hybrid powertrain|
|3||Hybrid powertrain||Infrequent start/stop favors waste heat recovery—no hybrid planned||Hybrid system type not specifiedf||Diesel-electric dual mode (series/parallel)|
|4||Road load management||GPS, adaptive cruise, driver feedback||Predictive cruise control using 3D digital map database (shown as an example in presentation)|
|5||Rolling resistance||Reduced rolling resistance||(Implied)||Super single tires/wheels|
|6||Axles||Smart axle (2-wheel/4-wheel drive)||Long-haul tandem (possibly 6 × 2)||Smart 6 × 2 tandem|
|7||Idle management||Solid oxide fuel cell APU||Fuel cell APU||Hotel-loads from hybrid|
|8||Weight reduction||Features TBD||Cross-membersf other features TBD||Cab and trailer composites, plastic fuel tanks, aluminum wheels/brake rotors, aluminum cross-members and driveshafts, carbon composite brake drums|
|10||Base engine (PCP, friction/parasitics)||Increased PCP, changes to combustion modes implied||In-cylinder pressure sensor||Combustion feedback|
|11||Fuel system||(Implied)||Bosch APCRS||Increased injection pressure, parallel gasoline injection option|
|12||Advanced LTC||Increased PCCI regime, lifted flame diffusion burn||PCCI studies||Diesel and gasoline injection (dual fuel)|
|13||Controls||Powertrain router as network coordinatorg||Features TBD||Features TBD|
|14||Electrically driven components||(Implied)||Some accessories||Some accessories|
|15||Waste heat recovery||Rankine cycle, mechanicaldrive to engine||Rankine cycle, drives electric generator and/or turbocompoundh||Rankine cycle, drives electric generator|
|Item No.||Technologies That the Teams Plan to Evaluatea||Industry/Government Lab/Academic/Trucking Fleet Teams|
|16||Aftertreatment||(Implied) SCR and engine-out NOx optimization||Minimize DPF regeneration; optimize PM-NOx|
|17||Turbo technology||Turbocharger with its own CVT Turbo compound transmissioni||Turbo compound, dual turbos|
|18||EGR loop||(Implied) (Implied)||Hybrid EGR (low/high pressure)|
|19||Variable valve technology||(Implied) (Implied)||Compression ratio control, cylinder deactivation|
NOTE: A summary of the three SuperTruck Team plans is shown. These projects are in response to the DOE’s FOA (DOE, 2010b). Entries described as “(Implied)” indicate that the companies had listed the topic, but without any elaboration to describe the approach they intend to take. It is not clear whether the “implied” technologies will be included in the final project, or what form the technologies might take.
Acronyms are listed in Appendix I. TBD, to be determined.
a Includes technologies suggested by the DOE, as well as suggestions from the contracting companies.
b Donald Stanton, “Cummins-Peterbilt SuperTruck Program,” presentation to the committee, September 9, 2010, Washington, D.C.
c Derek Rotz, “Daimler: DTNA/DDC R&D with DOE: PCC, NZ-50, Super Truck,” presentation to the committee, September 9, 2010, Washington, D.C.
d Anthony Cook, “Navistar’s SuperTruck Program,” presentation to the committee, September 9, 2010, Washington, D.C.
e CRADA: “Integrated Thermal and External Aerodynamics—Cummins,” Argonne National Laboratory, Jules Routbort, Merit Review, June 2010.
f Elmar Bockenhoff, “Daimler: Heavy Duty Diesels: The Road Ahead,” September 27, 2010, DEER Conference, Detroit, Mich.
g Donald Stanton, “High Efficiency Clean Combustion for SuperTruck,” September 29, 2010, DEER Conference, Detroit, Mich.
h Kevin Sisken, Detroit Diesel Corporation, “Increased Engine Efficiency via Advancements in Engine Combustion Systems,” September 29, 2010, DEER Conference, Detroit, Mich.
and “ride height lowered at highway speed” as potential new contributions.
Navistar and Daimler will investigate the optimization of an electric hybrid system, noting that even a modest (circa 6 to 9 percent) contribution may justify the complexity and expense of such systems, given the high fuel consumption of highway-duty-cycle tractor-trailer combinations. It appears that the two teams exploring electric hybrids plan to use substantially different systems.
All three companies have specific plans for managing hotel loads during extended idle periods. Idle reduction regulations have been imposed by 46 states and jurisdictions on the heavy-truck industry (see Chapter 6 for details). The states’ permitted idle time has an average limit of 5 minutes and a range of 0 to 15 minutes (usually per 6 to 8 hours, sometimes per hour) (ATRI, 2011). Cummins and Daimler plan to evaluate fuel cells to support hotel loads and reduce idle. As an alternative, Daimler is also pursuing a hybrid-electric solution that could manage the hotel loads. Thus, Daimler will evidently have two optional solutions to the idle-fuel-consumption problem. Navistar indicated that its hybrid-electric-system battery was expected to be able to handle the hotel load and idle reduction requirements.
Waste heat recovery utilizing a Rankine cycle was described by all three companies. Two different methods of energy utilization are being explored. Energy from the WHR system can be fed directly back to the crankshaft as mechanical energy, as shown in Figure 8-1. Another approach is to use the WHR energy to generate electricity for use by a hybrid system or to power electrical accessories. The WHR system as shown in Figure 8-1 is relatively complex and bulky, making packaging, reliability, and cost all significant issues to be overcome before this technology can be implemented in production.
A project phase-timing chart is a typical management tool for assessing and tracking the resources needed and expended for even moderately complex projects. It is not known if detailed charts were submitted to the DOE during the competitive bidding on the FOA, but such charts should have been part of the application deliverables. Two of the companies included extremely brief planning charts in their public presentations at the committee’s September 8-9, 2010, meeting. The chart from the Cummins presentation is nominally useful to perceive the project complexity and time frame but not adequately detailed to assess needed resources. For example, the Cummins schedule calls for a test cell demonstration of a 50 percent BTE engine by the end of 2011, a demonstration of the vehicle-level target at the end of 2012, a demonstration of more than 50 percent vehicle freight efficiency improvement over a 24-hour duty cycle by October 2013, and a demonstration of the 55
FIGURE 8-1 Cummins organic Rankine cycle waste heat recovery with energy returned mechanically to crankshaft. Acronyms are defined in Appendix I. SOURCE: Donald Stanton, Cummins, “Cummins-Peterbilt SuperTruck Program,” presentation to the committee, September 9, 2010, Washington, D.C.
percent BTE engine objective by June 2014. The Cummins schedule did not provide any additional detail regarding the company’s project plans. The chart from the Daimler presentation to the committee indicates only the overall project time frame but otherwise provides no additional details. Navistar did not include a project schedule in its presentation.
Evaluation of SuperTruck Program Goals
Although the SuperTruck program has well-defined goals, it leaves many very important details to the individual teams. The overall freight efficiency improvement needs to be measured on a specific duty cycle or combination of duty cycles. The selection of these duty cycles is left up to the contractors. Two of the contractors showed the committee plans to use a range of duty cycles rather than a single duty cycle in order to better evaluate the technologies. The SuperTruck FOA does specify that at least 75 percent of the duty cycle’s distance traveled must be representative of highway operation and that the vehicle shall operate at a weight of 65,000 lb. It is the committee’s understanding that the baseline truck will be tested at a gross combined weight (GCW) of 65,000 lb and that the same freight load will be carried by the SuperTruck prototype. This means that the test weight of the SuperTruck prototypes may be more or less than 65,000 lb, depending on changes in the weight of the empty vehicle. This means that the vehicle will be representative of a “cubed-out” operation, where the trailer is filled with low-density freight before the vehicle reaches the maximum legal weight, which is typically 80,000 lb. For long-haul trucks, about 60 percent cube-out, but there is a significant population (tankers, bulk haulers, haulers of high-density freight such as steel, etc.) that routinely “gross out.” Given the fact that the majority of trucks cube out, the committee is satisfied with the DOE’s selection of 65,000 lb total vehicle weight for the SuperTruck project.
The selection of duty cycle is very important, for several reasons. First, the selection of duty cycle can have a significant impact on the performance of specific fuel-saving tech-
nologies. For example, a constant 65 mph cruise cycle, with no grade, would highly favor aerodynamic improvements, but energy storage systems such as hybrid powertrains would have little or no benefit. A duty cycle that includes grades and lower-speed operation will give less emphasis to the benefits of aerodynamic improvements, but hybrid systems will offer a greater benefit. A duty cycle with no grades would also not capture the benefit of a feature such as predictive cruise control, which adjusts speed in anticipation of grade changes. One result of the requirement that the vehicle be tested at 65,000 lb is that there will be little fuel-consumption advantage in weight reduction, as well as little penalty for a weight increase. The committee’s understanding is that since a cubed-out situation is being represented, the freight load will be held constant, regardless of any change in empty vehicle mass. As a result, a 1,000 lb change in vehicle weight can be expected to cause only a 0.4 to 1.0 percent change in fuel consumption (NRC, 2010).
A second possible effect of duty-cycle selection is to make it easier or more difficult to reach the 50 percent vehicle fuel economy (33 percent fuel consumption) improvement target. This issue follows from the issues regarding the performance of specific technologies on a given duty cycle.
The third, and perhaps most important, issue surrounding the choice of duty cycle is the question of how well the selected duty cycle will represent “real-world” operating performance. This issue is not easy to resolve, because no one duty cycle can possibly represent all real-world truck operations, even within a fairly narrow segment such as heavy-duty long haul. Some operators often run with light loads, and others often operate at (or above) the maximum legal load. Some operators work in areas with little traffic where sustained constant-speed operation is possible. Some operators spend most of their time in or near large cities where congestion often restricts operating speed and where speed fluctuation is substantial. Some operators stay in areas with little grade, and others spend a lot of time in the mountains. All of these variations will have a substantial effect on fuel consumption and on the relative benefits of various fuel-saving technologies. There is no “one size fits all” solution.
The NRC report on medium- and heavy-duty vehicles showed that a fuel-consumption reduction of 50 percent is possible for a Class 8 tractor-trailer truck (NRC, 2010). This figure makes the 33 percent fuel-consumption target of the SuperTruck program appear relatively modest. However, several factors need to be taken into account. First, the NRC report used an “average” 2008 model truck as its baseline, whereas the SuperTruck program uses a “best-in-class” 2009 model as the baseline. The “average 2008” tractor would have a higher drag coefficient and higher rolling resistance tires than the best-in-class 2009 tractor, and the average 2008 trailer is without aerodynamic devices. In the NRC (2010) report, the “average 2008” vehicle was defined as having a drag coefficient Cd = 0.635, and a rolling resistance Crr = 0.0068. The SuperTruck contractors declined to reveal the Cd or Crr values for their 2009 best-in-class vehicles, but these should be significantly better. Second, the 50 percent fuel savings value in the NRC (2010) report included benefits from fleet management technology and driver training and coaching. These factors are not included explicitly in the SuperTruck program. Once these differences in baseline and scope are taken into account, the SuperTruck program targets match well with the NRC (2010) report’s projection of fuel savings available in the 2016 to 2020 time frame.
A number of 21CTP projects over the past several years have had as a goal the achievement of either 50 or 55 percent BTE from the engine. The engine section titled “Brake Thermal Efficiency Improvements” of Chapter 3 describes these projects and their results in detail. The 50 percent BTE target has proven to be a substantial challenge, which requires the use of expensive and complex technologies such as bottoming cycles. In 21CTP projects to date, technologies have been demonstrated individually which, if combined on a single engine, should provide a BTE of 50 percent (DOE, 2010a). However, there has not yet been a demonstration of a 50 percent BTE engine in a vehicle. In addition, the requirement for 50 percent BTE at cruise load poses an additional challenge, because the best point for BTE is typically at a higher load. This issue will be exacerbated by the fact that SuperTruck vehicle improvements will significantly reduce power demand at cruise, which will push the engine to a less efficient, lighter-load operating point at cruise. Given these considerations, the 50 percent BTE target appears to be a relatively risky, but not impossible, goal. The consensus of the committee is that the technical paths to achieving 55 percent BTE that the contractors will provide are indeed likely to include some “stretch” goals and some technologies that may prove impractical or extremely expensive. As technology progresses over time, the 55 percent target may become more feasible, but there are fundamental thermodynamics issues that will be difficult to overcome. The DOE Office of Vehicle Technologies Multi-Year Program Plan (DOE, 2010c, p. 2.3-2) states that “this activity will also conduct R&D on advanced thermodynamic strategies that may enable engines to approach 60 percent thermal efficiency.” Any consideration of BTE targets beyond 55 percent should be carefully examined in light of the laws of thermodynamics.
Evaluation of SuperTruck Team Plans
In addition to public presentations made to the committee by the Cummins/Peterbilt and Navistar teams, the committee visited the Cummins/Peterbilt team on November 8, 2010, and the Navistar team on January 13, 2011. These visits were made on a confidential basis, and so details of the plans that were discussed during these visits cannot be included in this report. The Daimler team presented its preliminary plans to the committee on a public basis on September 8-9, 2010.
The Daimler presentation used predictive cruise control as an example of how it intends to create predictive controls
for the engine, transmission, and vehicle.7 No details were offered on what these controls might do. The presentation lists the technologies that are planned for the SuperTruck program and offers a preliminary risk/benefit evaluation for many of these technologies. Many of the features that are planned fit the list suggested by the DOE. Some additional items added by the Daimler team include predictive engine controls, predictive vehicle controls, route-management and driver-feedback features, and the use of solar panels.
The Cummins/Peterbilt team presented a comprehensive plan that addresses a number of technology areas, including engine, transmission, bottoming cycle, tractor and trailer aerodynamics, weight reduction (or at least compensation for the weight of new components and systems), and rolling resistance.8 Additions to the DOE list of suggested technologies include a solid oxide fuel cell APU for idle elimination and a “smart axle,” which evidently shifts to 6X2 operation when high traction is not required. Adaptive cruise control and unspecified driver-feedback features are also part of the Cummins/Peterbilt plan. The team will not use a hybrid system, because its simulation work indicates that waste heat recovery has more potential in long-haul applications.
The Navistar team’s plan generally follows the list of technologies provided by the DOE. Notable additions include speed-adjusted ride height and an active 5th wheel for additional aerodynamic improvement.9 Navistar also plans to use a series/parallel hybrid system, by which the vehicle operates in series mode (diesel-electric) at low vehicle speeds and operates in parallel mode (with direct drive from the engine to the axle) at high speeds. The dual-mode hybrid system also allows for electric-only operation for short distances. Navistar will evaluate a dual fuel system (gasoline and diesel fuels) as part of its program to demonstrate an engine capable of 55 percent BTE. The Navistar plan also includes a very extensive range of weight-reduction features.
All three contractors have plans for evaluating the cost-effectiveness and potential payback of the technologies in their plans. A business case analysis for commercialization is one of the deliverables for the SuperTruck programs (DOE, 2010b). The committee believes that this cost-effectiveness evaluation is a critical part of the project and hopes that comparable methods and approaches will be used so that the results from the three contractors can be compared.
In general, the committee believes that all three SuperTruck projects have plans that offer the potential for meeting program goals. The plans also cover a wide range of technologies and allow for the evaluation of technologies over a range of operating conditions. One concern is that current plans do not call for all three SuperTrucks to be evaluated on a common duty cycle, since each team will develop its own duty cycle or cycles. This lack of a common duty cycle will make it more difficult to compare the performance of the three vehicles and the benefits of individual features and technologies at the end of the program.
The SuperTruck projects include a high level of effort and a high level of technical risk. Areas of risk include the following:
• Many of the fuel-saving technical features, such as hybrid systems, aerodynamic features, and bottoming cycles, add significant amounts of weight. A substantial amount of weight-reduction effort (and cost) will be required just to maintain the baseline vehicle weight.
• Some technologies, particularly bottoming cycles, are likely to pose significant reliability issues.
• Some technologies may not prove cost-effective, such as extensive weight reduction.
• Because each contractor will develop its own duty cycles and test protocols, it will not be possible to compare the results of the three programs directly.
To deal with the last area of risk, the committee believes that the contractors should calculate the fuel consumption for the baseline vehicle and engine and for the fully developed SuperTruck vehicle and engine, using the EPA and NHTSA fuel-consumption regulations. This will allow comparison of the improvements achieved by the three contractors. In addition, the committee believes that the three contractors and the DOE should agree on a single, “real-world” vehicle fuel-consumption test protocol (duty cycle) that will be used by all three contractors, in addition to the tests developed independently by each contractor. This common test would provide another data point that could be used to compare the accomplishments of the three SuperTruck projects.
Finding 8-1. The three SuperTruck projects will be the flagship projects under the 21CTP for FY 2011 through FY 2014; the goals are in concert with recommendations made in the 2008 NRC Phase 1 report. A large portion of the DOE 21CTP budget will be devoted to these three projects. Each SuperTruck project integrates a wide range of technologies into a single demonstration vehicle (engine, waste heat recovery, driveline, rolling resistance, tractor and trailer aerodynamics, idle reduction, weight reduction technologies, etc.), and the contractors are pursuing sufficiently different technical paths to avoid excessive duplication of effort. The results will help determine which fuel-saving technologies are ready and cost-effective for OEM-level product development programs.
7 Derek Rotz, Kevin Sisken, and David Kayes, Daimler and Detroit Diesel, “DTNA/DDC R&D with DOE; PCC, NZ-50, Super Truck,” presentation to the committee, September 9, 2010, Washington, D.C.
8 Donald Stanton, Cummins, “Cummins-Peterbilt SuperTruck Program,” presentation to the committee, November 15, 2010, Washington, D.C.
9 Anthony Cook, Navistar, “Navistar’s SuperTruck Program,” presentation to the committee, September 9, 2010, Washington, D.C.
Finding 8-2. Rather than have a number of targets for each subsystem, the SuperTruck projects have only two types of goals: one for the engine and one for overall vehicle fuel efficiency. This approach reflects the EPA and NHTSA approach to heavy-duty fuel efficiency regulations. Each project team is allowed to select a set of technologies that meet the project goals. The engine goal of 50 percent BTE for the demonstration vehicle appears to be feasible, although there is risk in being able to achieve it at a cruise condition. The engine goal of 55 percent BTE demonstrated in a test cell is very high risk but might be achievable. The overall vehicle goal of a 33 percent reduction in load-specific fuel consumption appears to be feasible.
Finding 8-3. Unfortunately, the SuperTruck program expresses vehicle efficiency targets in terms of fuel economy rather than fuel consumption. The vehicle target is stated as a 50 percent improvement in fuel economy rather than as a 33 percent reduction in fuel consumption. This can lead to confusion regarding the actual benefits of the program.
Recommendation 8-1. The DOE should state the SuperTruck program vehicle efficiency goals in terms of load-specific fuel consumption and track progress on this basis—that is gallons per 1,000 ton-miles, which is the metric used in the EPA/NHTSA fuel consumption regulations.
Finding 8-4. The committee believes that the SuperTruck project teams have developed plans that address the needs of the SuperTruck program and that have a reasonable chance for success. The keys to success include proper implementation of the plans along with the flexibility to adapt to new information and intermediate results during the course of the project.
Finding 8-5. The SuperTruck projects allow each team to design its own test duty cycle(s) within certain constraints. One negative consequence of this approach is that the three trucks may never be tested using a common cycle for comparison.
Recommendation 8-2. The DOE and the SuperTruck contractors should agree on at least one common vehicle duty cycle that will be used to compare the performance of all three SuperTruck vehicles. In addition, fuel consumption improvements should be calculated on the basis of the EPA and NHTSA fuel consumption regulations.
Finding 8-6. The SuperTruck projects go beyond the scope of previous 21CTP projects. Instead of relying entirely on simulations and laboratory testing, each of these projects will result in a drivable truck. The committee believes that it is important to take technologies that have been developed to date and implement them in a real vehicle. Often, the implementation of new technologies in real-world applications yields unexpected results, and these results must be explored before any new technology can be considered ready for production implementation.
ATRI (American Transportation Research Institute). 2011. Idling Regulations Compendium. Available at http://www.atri-online.org/index.php?option=com_content&view=article&id=164&Itemid=70. Accessed January 18, 2011.
DOE (U.S. Department of Energy). 2010a. Secretary Chu Announces $187 Million to Improve Vehicle Efficiency for Heavy-Duty Trucks and Passenger Vehicles. Washington, D.C. Available at http://www.energy.gov/8506.htm.
DOE. 2010b. Funding Opportunity Number: DE-FOA-0000079. U.S. Dept of Energy, Recovery Act—Systems Level Technology Development, Integration, and Demonstration for Efficient Class 8 Trucks (SuperTruck) and Advanced Technology Powertrains for Light Duty Vehicles (ATP-LD), DE-FOA-0000079. August 24. Washington, D.C.: Department of Energy. Available at http://www.energy.gov/recovery/documents/zeDE-FOA-0000079.pdf.
DOE. 2010c. Multi-Year Program Plan 2011-2015. December. Washington, D.C.: Office of Vehicle Technologies.
NRC (National Research Council). 2008. Review of the 21st Century Truck Partnership. Washington, D.C.: The National Academies Press.
NRC. 2010. Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles. Washington, D.C.: The National Academies Press.