This third review by the National Academies of Sciences, Engineering, and Medicine1 Committee on Review of the 21st Century Truck Partnership (21CTP), Phase 3, hereinafter called the committee, follows on the Phase 1 and Phase 2 reviews by the National Research Council (NRC, 2008; 2012). The 21st Century Truck Partnership (21CTP—or, sometimes, “the Partnership”) is a cooperative research and development (R&D) partnership made up of four federal agencies and 15 industrial partners.2 The Partnership aims to “accelerate the introduction of advanced truck and bus technologies that use less fuel, have greater fuel diversity, operate more safely, are more reliable, meet future emissions standards, and are cost effective” (21CTP, 2013). It supports research, development, and demonstration (RD&D) that can lead to commercially viable products and systems. Its strategic approach includes (1) develop and implement an integrated vehicle systems R&D approach that validates and deploys advanced technology; (2) promote research on engines, combustion, exhaust aftertreatment, fuels, and advanced materials; (3) promote research on advanced hybrid propulsion systems; (4) promote research to reduce vehicle power demands; (5) promote the development of technologies to improve truck safety, (6) promote the development and deployment of technologies that substantially reduce energy consumption and exhaust emissions during idling; (7) promote the validation, demonstration, and deployment of advanced truck and bus technologies, and improve their reliability to the point where they can be adopted in the commercial marketplace; and (8) research, validate, and deploy technologies and methods that save fuel through more efficient operations of trucks and transportation systems, with an overall goal of better freight efficiency (21CTP, 2013).
The majority of the federal funding for RD&D projects supporting the goals of 21CTP comes from the DOE’s Vehicle Technologies Office (VTO), with funds from the other three agencies as well. The American Recovery and Reinvestment Act of 2009 (ARRA, also known as the “stimulus”) injected additional funding during the past few years in the SuperTruck program, supporting part of the four teams conducting R&D and integrating a variety of technologies into Class 8 tractor-trailer demonstration vehicles.
With the focus of the Partnership on reducing fuel consumption and following on the NRC Phase 2 report (NRC, 2012) and the National Highway Traffic Safety Administration/Environmental Protection Agency (NHTSA/EPA) regulations that are being promulgated to reduce fuel consumption and greenhouse gas (GHG) emissions from medium- and heavy-duty vehicles (MHDVs), the Partnership has an important role to play in bringing together the government agencies and the private sector companies.3 The Partnership is a means for facilitating communication among four government agencies, the national laboratories, and the private sector. Through regular meetings and exchanges of information on the various projects that are being funded, it seeks to avoid duplication of R&D efforts and identify industry needs for R&D projects, which then create a higher
1 Effective July 1, 2015, the institution is called the National Academies of Sciences, Engineering, and Medicine. References in this report to the National Research Council are used in a historic context identifying programs prior to July 1.
2 The agencies are the Department of Energy (DOE), Department of Transportation (DOT), Department of Defense (DOD), and U.S. Environmental Protection Agency (EPA). The 15 industrial partners are Allison Transmission, ArvinMeritor, BAE Systems, Caterpillar, Cummins Engine, Daimler Trucks North America (Freightliner and Detroit Diesel), Eaton Corporation, Honeywell International, Navistar, Mack Trucks, NovaBUS, Oshkosh Truck, PACCAR, and Volvo Trucks North America.
3 NHTSA/EPA issued a Phase 1 regulation for model years 2014 to 2017 and issued a Notice of Proposed Rulemaking in June 2015 for a Phase 2 regulation covering model year 2018 and beyond.
likelihood that they will help the private sector develop products that can be commercially deployed and reduce fuel consumption, GHG emissions, and meet criteria pollutant standards. Although this is not a centrally directed program with a single-point authority over budgets and priorities, the Partnership has made good progress since the NRC Phase 1 and 2 reviews in improving communications, coordination and collaboration among the partners, documenting most of the projects and budgets under the 21CTP umbrella, and making some impressive technical progress in selected areas under its umbrella.
21CTP has become increasingly important in carrying out fuel consumption R&D as the federal government issues MHDV fuel consumption regulations. In addition, anticipated emission standards for oxides of nitrogen (NOx) in California and possibly at the federal level may affect engine and emission control technologies that will be deployed. These regulatory measures regarding fuel consumption as well as emissions imply that the federal government has a role, and perhaps an increasing role, in the development of technologies to help the private sector achieve these policy goals and also to help U.S. firms remain competitive in the face of international competition. The Partnership plays an important role in bringing together, to the extent possible, a wide variety of different groups in a fairly fragmented trucking industry that does not have an overall organization that coordinates long-term R&D. As pointed out in the NRC Phase 1 report,
very few U.S. manufacturers of trucks and buses or heavy-duty vehicle components have the R&D resources to develop new technologies individually. The 21CTP is giving some of those companies access to extraordinary expertise and equipment of the federal laboratories, in addition to seed funding that draws financial commitment from the companies to push forward in new technology areas (NRC, 2008).
A number of important accomplishments, which are addressed in more detail in the remainder of this Summary and in the report, have occurred since the earlier NRC reviews:
- The engine systems Goal 1 of a 50 percent brake thermal efficiency (BTE) for an emissions compliant engine has been achieved. A pathway to achieve 55 percent is being developed (Chapter 3).
- The four SuperTruck projects jointly funded by DOE and the private sector are impressive projects that integrate a wide variety of engine and vehicle technologies to significantly reduce the fuel consumption of Class 8 tractor-trailer vehicles, which consume the greatest part of the fuel used in the United States for heavy vehicles. These efforts follow on the recommendations in the NRC Phase 1 report for the full system integration of technologies and away from component-only R&D. These projects have brought together a wide variety of companies, the national laboratories, and universities (Chapter 8).
- The SuperTruck projects incorporated a number of vehicle power demand technologies that accounted for about 56 to 74 percent of the total fuel consumption reductions, with 26 to 44 percent coming from engine efficiency improvements (Chapter 8).
- Following on previous NRC recommendations, the DOE has proposed the development of an annual dedicated report on 21CTP activities and gave the committee a first draft proposal (Chapter 2).
- Hybrid vehicle systems have demonstrated significant fuel consumption and emissions reductions in a number of MHDV applications, but their cost prohibits commercial deployment, especially at foreseeable fuel prices. In addition, the SuperTruck project results thus far show a limited potential benefit on long-haul duty cycles for hybrid systems using currently available technology. The 21CTP hybrid team is considering a proposal to restructure its mission and focus, which the committee supports (Chapter 4).
The committee notes, however, that there are still remaining issues that the Partnership should continue to endeavor to address, some of which have been of concern in the Phase 1 and 2 reviews as well:
- The Partnership has identified particular areas to address but in some areas research funding has not been commensurate with the goals for those areas. In some cases, e.g., efficient operations or hybrid vehicles, funding has been insufficient to meet the goals. In those areas that have not received funding, adjustments to the goals should be made.
- The Partnership needs to develop an ongoing and systematic approach to identify which projects fall under the 21CTP umbrella and how they contribute to the Partnership’s goals, as well as monitoring the results of the projects relative to the goals on an ongoing basis.
- The Partnership has yet to develop a brief annual report but, as noted above, is in the process of developing one.
- Previous reviews have suggested that additional truck manufacturers and suppliers be recruited for membership to the Partnership but the members have remained the same. With the changes occurring in the industry, this should be revisited.
- Given the expected constraints on future budgets, it will probably be increasingly important to identify the federal government’s role after assessing both domestic and overseas heavy-duty vehicle R&D. Assessing overseas R&D was recommended in previous reviews but it is not clear whether this was ever conducted.
The technology integration efforts of the SuperTruck projects led to significant efforts by the project teams to address component R&D of engine idle reduction (Chapter 6) and vehicle power demands (Chapter 5, e.g., aerodynamics of the tractor and trailer, tire rolling resistance, friction reduction, weight reduction, and other approaches to reducing fuel consumption). Consequently, because they have been addressed in the SuperTruck projects, these areas have received much reduced funding through DOE for individual projects in these areas. Furthermore, the relatively new area of efficient operations (Chapter 9) has not received much emphasis because of lack of funding. The discussion of these areas is left to the individual chapters and not included in the Summary.
Since the previous Phase 1 and 2 reviews, the Partnership has evolved in the face of changing budgets and new initiatives. The main leadership resides with the DOE’s VTO, which manages a number of DOE-funded RD&D programs directly related to MHDV technologies. The other agencies simply bring their own existing programs that are relevant to the goals of the 21CTP under the 21CTP umbrella. The other complicating factor is that the budgetary aspects of the different agencies are all controlled by different committees in Congress. Consequently, the Partnership is unlike a traditional R&D program with central control and responsibility for budgets and priorities. DOE staff organize meetings and conference calls, maintain the information-flow infrastructure (such as websites and e-mail lists), and have led the discussions for and preparation of the updated 21CTP roadmap and white papers laying out Partnership goals, which was issued in February 2013 (21CTP, 2013). The management of individual projects under the 21CTP umbrella rests with the individual federal agencies that have funded the work. These agencies use the 21CTP information-sharing infrastructure to coordinate efforts and ensure that valuable R&D results are communicated and that overlap of activities is reduced. As was noted in the NRC Phase 2 report, the NRC’s review of the overall 21CTP has helped to communicate to the various stakeholders and Congress the ongoing R&D efforts in the agencies and on the various projects (NRC, 2012).
The NRC Phase 2 review called for the preparation of a specific list of projects within each agency deemed to fall under the 21CTP umbrella, the associated line-item funding, and the overall budget for 21CTP. While DOE was able to provide this information for its own projects, the previous reviews were not able to secure this information from DOT, DOD or EPA. The situation has improved in this Phase 3 review: Led by DOE, the Partnership provided an inventory of projects categorized as falling under 21CTP, with the associated funding levels (see Appendix D and Figure 1-1 in Chapter 1).
Finding 2-1. The 21CTP remains a virtual organization facilitating communication among four government agencies, the national laboratories, and industry, led by DOE but with no single-point authority over its activities, priorities, or budgets. While far from optimal, this structure is necessitated by the separate reporting and budgeting mechanisms for each agency. Led by DOE, the Partnership has made good progress in adapting to this reality by improving communications, coordination, and collaboration among the partners, and documenting most of the projects and budgets under the 21CTP umbrella.
Recommendation 2-1. The DOE is urged to continue this improvement by maintaining and publishing the inventory of projects and budgets across all four agencies, tying those projects into the specific 21CTP goals and promoting the use of a portfolio management approach or the DOE’s Office of Energy Efficiency and Renewable Energy’s Project Management Center (EERE PMC) equivalent within the other agencies. Furthermore, EPA, DOT, and DOD should appoint a dedicated counterpart to DOE’s designated 21CTP leader, who in turn should report directly to the director of the Vehicle Technologies Office on 21CTP matters.
Recommendation 2-2. The Partnership should develop and adopt criteria for including projects under the 21CTP umbrella, such as “Does the project clearly address one of the specific goals of 21CTP?” and “Does the project fall within the R&D interests of the member Partners of the 21CTP?” The committee recognizes that there will be at least two levels of projects—those tightly connected to specific 21CTP goals and a supporting set of projects that have a longer term impact. Better definition of the criteria for including a project and at what level would assist in evaluating and increasing the effectiveness of the Partnership.
“Engine systems” comprises the engine, the aftertreatment, and the fuel as an interlinked system. Two 21CTP engine goals are focused on a significant increase in energy efficiency: (1) develop and demonstrate an emissions compliant engine system for Classes 7 and 8 highway trucks that achieves 50 percent BTE in an over-the-road cruise condition and (2) achieve 55 percent BTE in prototype engine systems in the laboratory. R&D on engine systems includes the projects funded by DOE and, in some cases, cost-shared with industry; these range from fundamental experimental work, to kinetic mechanism development, to mechanism evaluation and simplification, to development of advanced numerical methods, and to further development of the computational codes. The advanced combustion engines program is well managed and there is good collaboration and synergy among the DOE 21CTP individual engine projects. The SuperTruck engine projects were instrumental in meeting Goal 1, 50 per-
cent BTE, and in carrying out the research to define a path to meeting Goal 2, 55 percent BTE. Of the federal funding for the SuperTruck teams, the amounts spent on diesel engine systems R&D to achieve the 50 and 55 percent BTE goals are approximately these: Volvo, $7.6 million; Navistar, $12.7 million; Daimler, $15.8 million; Cummins, $15.5 million.
Finding 3-1. The 21CTP has successfully met Goal 1, to develop and demonstrate an emissions-compliant diesel engine system for Class 7 and 8 highway trucks that achieves 50 percent brake thermal efficiency in an over-the-road cruise condition. The engine uses a waste heat recovery system.
Finding 3-2. The projects in the engine systems portion of 21CTP represent a closely coordinated set of research activities that are pursuing a better fundamental understanding of processes critical to efficient engine operation. Fundamentals associated with fuel injection, sprays, gas exchange, in-cylinder flows, advanced combustion processes, plus comprehensive yet robust kinetic routines for realistic fuels are being investigated. The learning from these activities is being incorporated into models, both detailed and phenomenological, that serve as tools for advanced engine development. Integral to this effort is the continued advancement of the base computer program itself and the solvers that facilitate rapid computational turnaround time. The program is well managed and interfaces well with industry stakeholders.
Recommendation 3-1. With the increased importance of advanced computational fluid dynamics (CFD) for developing the engines and operating scenarios necessary for minimum fuel consumption and in light of DOE’s role in the generation of new knowledge that gets incorporated into these CFD codes as submodels, a critical review of the Partnership’s program to develop the next-generation code (KIVA 4) should be performed. Feedback from participants in the high-performance computing workshop should be matched against the current code development activities, and the adequacy of the current program should be assessed. If necessary, the next-generation code development should be adjusted.
Finding 3-5. Achieving Goal 2, 55 percent BTE in a laboratory engine, will be very challenging. This is a high-risk, high-reward fundamental research program. It is an important stretch goal because it will facilitate identifying the potential of different advanced engine, fuel, and combustion concepts for increased engine efficiency, even though these concepts may not be commercially viable in the near future.
Recommendation 3-2. The fundamental diesel engine research program pursuing advanced technologies and combustion processes and engine architectures to achieve 55 percent BTE should continue to be a focus of the 21CTP engine activities. However, the experiments and modeling should maintain a focus on dynamometer R&D, as opposed to attempting to build a demonstration vehicle. The achievement of this goal should be extended from 2015 to 2020 in order to have sufficient time to carry out R&D on this stretch goal. Also, this activity should not be at the expense of efforts to reduce load-specific fuel consumption via system integration and road load reductions.
The considerable effort and research funding focused on improving diesel emission control systems is important to the development of the system and the engine in the vehicle relative to the system cost, weight, and volume.
Finding 3-6. The research agenda for 21CTP is focused on a wide diversity of heavy-duty emissions control work. There are impressive fundamental studies on selective catalytic reduction (SCR) catalysts, diesel particulate filter (DPF) fundamentals, low-temperature SCR and oxidation catalysts, passive NOx adsorbers, multifunctional components, emissions measurement and modeling, system models, fuel effects, aging, and sensor development. These programs are delivering valuable results, but there are no program goals to guide future directions.
Recommendation 3-3. The DOE should develop specific aftertreatment goals for the 21CTP. These goals will serve as a focal point for researchers to submit proposals and for the DOE to assess them.
Recommendation 3-4. The Partnership should continue to fund work on improved SCR NOx efficiency (mainly low-temperature efficiency without compromising high-temperature efficiency) and aging and poisoning effects. California’s and, potentially, EPA’s move toward further heavy-duty NOx reductions to meet National Ambient Air Quality Standards for ozone will be critical. These new targets need to be set for the research efforts.
Finding 3-8. To achieve 50 percent BTE in the SuperTruck Program (Chapter 8), the engine compartment has limited space for the cooling system, the waste heat recovery system, and the aftertreatment system. The aftertreatment system volume, weight, and cost are important for the design of the engine compartment for trucks that are developed for 50-55 percent BTE.
Recommendation 3-6. Technologies such as an SCR catalyst on a DPF or others that have the potential to reduce the volume, weight, and cost of the aftertreatment system should be a part of the program to develop a 55 percent BTE engine.
Finding 3-10. A series of fuels for advanced combustion engines (FACE) and surrogates have been identified in cooperation between the DOE and the Coordinating Research Council (CRC). These fuels have specific physical and chemical properties and are being used in several advanced combustion research programs, including the evaluation of various low-temperature combustion concepts, the development of CFD models for in-nozzle flow, spray formation, and combustion, and the development of new analytical techniques.
Recommendation 3-8. The DOE should continue to explore how the United States might use its abundant petroleum, natural gas, and biofuel resources in the most efficient manner. Studies, some of which are under way that contribute to this objective, should strive to answer the following questions:
- What fuel properties (e.g., ignition characteristics, volatility, composition) of diesel fuel and gasoline provide for maximum efficiency of various advanced combustion engines? FACE and a common set of surrogate fuels should be utilized by all DOE facilities involved in combustion research programs in order to provide consistent fuel characteristics when evaluating laboratory experiments and engine test results.
- Based on well-to-tank analyses, what fuel properties and processing procedures result in the lowest GHG emissions for hydrocarbon-based and bio-based fuel components?
Hybrid systems have demonstrated significant fuel consumption and emissions reductions in a number of MHDV applications, but cost effectiveness has been a barrier faced by many of today’s hybrid drive manufacturers. As fuel consumption and GHG emissions standards become more stringent, however, there is a need for 21CTP to support the development of advanced technologies such as battery-electric and hybrid drives that will help meet these goals. The cost of hybrid drive equipment is not likely to fall sufficiently fast to meet commercially acceptable cost/benefit ratios in the near future. As a result, there is a need for 21CTP to support R&D that will in time lead to commercially viable hybrid drive technologies.
Finding 4-1. The 21CTP is considering a proposal to restructure its hybrid team so that it can work on drivetrain efficiency improvements, including other types of system integration opportunities that incorporate hybrid drive equipment.
Recommendation 4-1. The 21CTP hybrid team is encouraged to use this opportunity to redefine its mission in a manner that will lead to vehicle efficiency and emissions reduction improvements via a range of technology options, including promising opportunities for electrification and other types of innovative drivetrain improvements. During the course of this restructuring, the six R&D stretch goals developed in 2011 for the MHDV hybridization program should be redefined as part of the development of strategic objectives of the restructured advanced drivetrain initiative. At the conclusion of this process, the 21CTP leadership, working together with DOE and the other 21CTP partner federal agencies, should make a serious effort to secure funding to pursue whatever goals emerge so that they have a realistic chance of being achieved.
Finding 4-2. Several manufacturers have commercialized medium-duty hybrid trucks during the past several years and successfully demonstrated their ability to significantly reduce fuel consumption and emissions, particularly in vocational4 and delivery truck applications. Despite this progress, the high cost of the hybrid drive train equipment and batteries combined with dropping prices for natural gas and oil have significantly retarded their market penetration in the United States. This has caused economic hardships for many hybrid truck manufacturers, causing a widespread reevaluation of the current hybrid truck business viability, at least in North America. At the same time, there is evidence that business opportunities for MHDV hybrid equipment are growing in other parts of the world, particularly in China, where government mandates are having a major impact.
Recommendation 4-2. Recognizing the advantages that hybridization can offer in trucks, 21CTP should support the development of new technology that offers promise for significantly improving the performance and cost-effectiveness of hybrid truck technology in the longer term. Project opportunities should be pursued to evaluate cost-effective vehicle electrification configurations for trucks, including hybrid drives with optimized component ratings to minimize their payback periods in different vehicle classes and applications. This future work should take advantage of technology advances originally made and commercialized for light-duty vehicles, including new battery technologies as well as opportunities for integrated microelectrification of truck functions such as start/stop operation, idle reduction, waste heat recovery, engine starting, and accessory electrification.
Finding 4-3. Although EPA and NHTSA have made considerable progress toward specifying the certification proce-
4 Vocational vehicles cover a wide range of vehicles, including delivery trucks, dump trucks, cement trucks, buses, cranes, bucket trucks, and others. They are typically sold as an incomplete chassis with multiple “outfitters,” such as an engine manufacturer, a body manufacturer, and an equipment manufacturer.
dures for fuel consumption and emissions in hybrid MHDVs, these procedures are still incomplete and imprecise in some important areas, particularly with regard to chassis dynamometer testing of complete hybrid MHDVs, and dynamometer testing of hybrid drivetrain power packs to determine their emissions and fuel consumption performance.
Recommendation 4-3. 21CTP should make it a priority to encourage EPA and NHTSA to accelerate their efforts to strengthen and finalize procedures for certifying the fuel consumption and emissions of hybrid MHDVs, including procedures for chassis dynamometer testing of complete hybrid vehicles and dynamometer testing of hybrid propulsion drivetrains alone. The 21CTP leadership is encouraged to work together with EPA and NHTSA to inform and educate the 21CTP stakeholders and the broader MHDV manufacturing community about the details of these procedures when they become available.
The 21CTP includes goals to ensure that advancements in truck design and technology to improve fuel efficiency do not have negative impacts on safety, and ensure that efforts to improve safety do not reduce efficiency.
Finding 7-3. The current generation of commercially available Forward Collision Avoidance and Mitigation (F-CAM) systems should reduce fatalities in truck-striking rear-end collisions by 24 percent, injuries by 25 percent, and property damage only crashes by 9 percent. Second- and third-generation versions of the systems will bring substantially greater benefits.5
Recommendation 7-3. 21CTP should assess future generation Forward Collision Avoidance and Mitigation (F-CAM) system development in order to identify barriers to development and establish incentives to foster commercialization.
An important and major component of the 21CTP during the past 5 years has been the SuperTruck program that was designed to reduce the fuel consumption of Class 8 long-haul tractor-trailer freight trucks. These SuperTruck vehicles are employing and integrating a wide range of technologies, many of which have been developed at the component or subsystem level under various 21CTP projects. The SuperTruck program aligns with the findings and recommendations set out in the NRC Phase 1 review (NRC, 2008). Four project teams have been awarded funding, with ARRA funding providing support to two of the teams (Cummins–Peterbilt and Daimler). With 50/50 cost sharing between government and industry, the total engine and vehicle funding for the project teams is $77.7 million for Cummins–Peterbilt; $79.1 million for Daimler Trucks North America; $76.2 million for Navistar; and $38 million for Volvo, for a total of about $284 million. Two teams, Cummins–Peterbilt and Daimler, aimed at completing their projects late 2014/early 2015 and their demonstration vehicles. The Navistar and Volvo teams will wind up in 2016. It should be emphasized that the teams have numerous companies, national laboratories, and universities working with them. With this funding for comprehensive demonstration vehicles incorporating many technologies, the teams are addressing areas such as engine efficiency, hybridization, aerodynamics, rolling resistance, idle reduction, and lightweight materials that prior to SuperTruck were only addressed through the core VTO projects.
The four project teams were awarded projects under the SuperTruck program and given the same basic targets, along with a requirement to maintain “comparable vehicle performance”:
- Achieve 50 percent BTE from the engine at a cruise operation speed and load point,
- Demonstrate a path to 55 percent BTE from the engine, and
- Demonstrate a 50 percent increase in freight efficiency, measured in freight ton-miles per gallon, on a long-haul drive cycle.
In addition to these targets, the Cummins and Daimler teams added a target to measure the effectiveness of their auxiliary power unit (APU) systems, which handle hotel loads when the vehicle is parked: Demonstrate a 68 percent increase in freight efficiency on a 24-hour duty cycle (drive cycle plus overnight hotel load).
Finding 8-1. Overall, the committee finds the SuperTruck program to be a great success and finds that the system integration aspect of SuperTruck was a key to the program’s success. The SuperTruck program drove technology development at a faster pace than industry would have achieved on its own. SuperTruck teams used the program to do the following:
- Increase both test and analysis capabilities, and improve the correlation between test and analysis;
- Use simulation results to drive improved experimental techniques, and use experimental results to help improve simulation techniques;
- Integrate combinations of technologies that had never been tested on a complete vehicle;
- Learn about opportunities, issues, and trade-offs with fuel saving technologies in real-world vehicle testing; and
5 Second-generation systems will be able to detect stationary threat objects in the roadway through the fusion of radar and vision systems, while third-generation systems will have more aggressive automated braking deceleration, achieving 0.6 g.
- Understand the challenges that must be overcome in order to make certain technologies cost effective.
Finding 8-2. The Cummins and Daimler SuperTruck teams have met the goal of an engine with 50 percent brake thermal efficiency (BTE) at the cruise power point, and the other two teams are working to meet this goal. The Cummins and Daimler teams have also exceeded by a wide margin the goal of a 50 percent increase in freight efficiency (33 percent reduction in load-specific fuel consumption [LSFC]) over a long-haul drive cycle. The other two teams are working to meet or exceed the program goal in 2015 (Volvo) and early 2016 (Navistar).
Finding 8-3. The Cummins–Peterbilt SuperTruck team has comfortably exceeded a self-imposed goal of a 68 percent increase in freight efficiency (40.5 percent reduction in LSFC) over a 24-hour long-haul duty cycle. It achieved an 86 percent increase in freight efficiency (46 percent reduction in LSFC). The Daimler team demonstrated a 115 percent increase in freight efficiency (53.5 percent reduction in LSFC) on a different 24-hour duty cycle. This 24-hour goal does not apply to the Volvo program, and Navistar’s status is to be determined.
Finding 8-6. Using the results available to date, about 26 to 44 percent of the total vehicle fuel savings are due to engine efficiency improvements, while about 56 to 74 percent are due to vehicle power demand reduction. In the Cummins–Peterbilt project, 42 percent of fuel savings are due to the engine and waste heat recovery, 14 percent to tractor aerodynamics, 28 percent to trailer aerodynamics, and 15 percent to tire and driveline improvements. In the Daimler SuperTruck, engine improvements account for 26 percent of the total fuel savings while 74 percent is a result of vehicle power demand reductions, including the effect of the hybrid system.
Finding 8-7. SuperTruck project results show a limited potential benefit on long-haul duty cycles for hybrid systems using currently available technology. Much of the benefit of a hybrid system can be captured with much less expensive and heavy alternatives, such as a GPS-based cruise control that uses the vehicle as a kinetic energy storage device. Microhybrid systems (smart control of auxiliary power demand, possibly combined with limited energy storage to handle auxiliary and/or hotel loads) may prove to be a more promising hybrid approach for long-haul trucks.
Finding 8-9. The SuperTruck vehicles incorporate technologies with a wide range of production readiness: Some will go into production soon; some will never become cost-effective with technology that is now known. The outstanding fuel savings achieved in this program thus need to be treated carefully. Actual production vehicles achieving SuperTruck fuel savings may not be cost-effective for several decades unless fuel costs increase substantially.
Recommendation 8-1. The SuperTruck demonstration vehicles represent a huge investment. DOE should consider ways of extracting additional research results from this investment by using the trucks that have been built to evaluate additional technologies. Some possibilities include these:
- Evaluation of additional technologies, such as microhybrid;
- Comparison of SuperTrucks on identical test cycles, with additional work to help understand any differences in performance;
- Vehicle evaluation of hardware resulting from future system or subsystem research projects;
- Exploration of a range of routes and payloads to determine the sensitivity of technologies to various applications.
Recommendation 8-2. Because of the great value demonstrated by the SuperTruck program, DOE should be working on at least one vehicle integration project at any given time. Owing to likely funding limitations, it will not be possible to have three or four similar projects running. A range of integration projects are possible, including these:
- A regional haul SuperTruck,
- A heavy-duty vocational SuperTruck (refuse, dump, etc.),
- A SuperTrailer program to help trailer manufacturers build engineering capability, and
- A delivery truck of Class 3, 4, 5, or 6.
Finding 8-12. Although it did not conduct a detailed safety analysis, the committee believes that it is unlikely that most of the efficiency technologies under consideration in the SuperTruck program will have a negative impact on safety.
Recommendation 8-5. It is important for the 21CTP, probably through DOT, to monitor and analyze in detail the technologies implemented in the SuperTruck projects to verify that they do not have a negative effect on safety, since one or more of the technologies may be considered for future production vehicles.
Finding 8-13. DOE is still using fuel economy (FE) in miles per gallon and freight efficiency in ton-miles per gallon for their fuel use metric, while the NHTSA regulations that were published 5 years ago use fuel consumption (FC) in gallons per 100 miles and load-specific fuel consumption (LSFC) in gallons per 1,000 ton-miles.
Recommendation 8-6. DOE should use FC and LSFC in its studies in order to be consistent with EPA/NHTSA regulations and to provide in the literature the percent improvements in magnitudes that relate to the metrics used in the regulations. Also, DOE needs to be a leader in changing the culture so that FC and LSFC become accepted metrics by industry.
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.
NRC (National Research Council). 2008. Review of the 21st Century Truck Partnership. Washington, DC: The National Academies Press.
NRC. 2012. Review of the 21st Century Truck Partnership, Second Report. Washington, DC: The National Academies Press.