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--> Executive Summary This is the fifth report by the National Research Council Standing Committee to Review the Research Program of the Partnership for a New Generation of Vehicles (PNGV). The PNGV program is a cooperative research and development (R&D) program between the federal government and the United States Council for Automotive Research (USCAR), whose members are DaimlerChrysler Corporation, Ford Motor Company, and General Motors Corporation. One of the aims of the program, referred to as the Goal 3 objective, is to develop technologies for a new generation of vehicles that could achieve fuel economies up to three times (80 mpg) those of comparable 1994 family sedans. At the same time, these vehicles must be comparable in terms of performance, size, utility, and cost of ownership and operation and meet or exceed federal safety and emissions requirements. The intent of the PNGV program is to develop concept vehicles by 2000 and production prototype vehicles by 2004.1 In this report, the committee again examines the overall adequacy and balance of the PNGV research program to meet the program goals and requirements (i.e., technical objectives, schedules, and rate of progress), as well as the use of ongoing systems analysis to guide R&D, progress towards meeting long-range component and system-level cost and performance goals, progress in research on 1 Goal 1 is to improve national competitiveness in manufacturing significantly. Goal 2 is to implement commercially viable innovations from ongoing research on conventional vehicles. Because the Goal 3 concept vehicle demonstrations are focusing on relatively near-term technologies, the distinctions between goals 1, 2, and 3 are becoming blurred. For the most part, the committee has focused on efforts to meeting Goal 3.
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--> vehicle emissions and advanced materials, and efforts to provide interfaces among government R&D projects in support of the PNGV. This Executive Summary highlights the committee's principal findings and recommendations; detailed recommendations can be found in the body of the report. Progress and Major Achievements The updated PNGV Technical Road Map, which details performance objectives and lays out milestones and schedules in each major technology area, provides a good summary of program goals. Since the PNGV technology selection process was completed at the end of 1997 (reviewed in the fourth report), technical developments have been focused on the following technology areas: (1) four-stroke direct-injection (4SDI) engines, including compression-ignition direct-injection (CIDI) engines and spark-ignition direct-injection engines; (2) fuel cells; (3) batteries for energy storage; (4) power electronics and electrical systems; (5) structural materials; and (6) manufacturing processes. Efforts are also under way to reduce energy losses by improving vehicle aerodynamics, reducing rolling resistance, improving the efficiency of vehicle accessories, and recovering energy and storing it in the batteries during vehicle braking. In the past year, more progress was made towards meeting PNGV goals than in previous years of the program. In the view of the committee, much of this progress can be attributed to the attitude and efforts of the PNGV technical teams, which appear to be working more cooperatively towards meeting common goals than in past years. The committee considers this to be a very positive change that has provided a needed boost to continuing technical productivity. The PNGV also responded positively to most of the committee's recommendations in the fourth report. Four-Stroke Direct-Injection Engines The USCAR partners are making good progress toward meeting their targets, with the exception of emissions and cost targets, which still present significant challenges. Because the engine systems are still under development, emissions controls and costs are either unknown or at a very early stage of optimization. A number of notable accomplishments have been made for CIDI engines, including the development of a prototype fuel-injection system with desirable operating characteristics, especially in terms of controlling for specific power and noise; regulating vibration and harshness; improving the understanding of fundamental, in-cylinder combustion processes; reducing particulate emissions through fuel modifications; developing a fueling system for dimethyl ether (a possible alternative fuel); and developing lean-NOx catalyst systems that have demonstrated promising removal rates.
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--> Fuel Cells Although major obstacles must still be overcome to meet the targets for realizing a practical, automotive fuel-cell system, impressive progress has been made in the past year. For example, in the area of fuel processors (converting gasoline to hydrogen for use by the fuel cell), a steady-state partial-oxidation gasoline reformer and carbon monoxide cleanup system has exhibited good results, and the development of a 50-kW preferential oxidation system has allowed the first meaningful transient measurements. In the area of fuel-cell stacks, important cost reductions have been identified with composite bipolar plates and continuous manufacturing processes, and the tolerance to carbon monoxide was increased to 100 ppm. In the area of systems integration, a significantly improved systems analysis model has been developed and transferred to the fuel-cell developers. Batteries The electrochemical battery is still the most promising technology for energy storage in hybrid electric vehicles (HEVs). The development of cells and modules continues apace, as does abuse and safety testing. Programs have been initiated for 50-V modules. For lithium-ion batteries, energy and power goals appear to be attainable, but meeting cycle-life and calendar-life targets is questionable. The lithium-ion technology uses organic materials that can burn, and disquieting fire and smoke have been observed in some tests. The nickel metal hydride system uses an aqueous electrolyte, which eliminates many of these problems. The PNGV now recognizes that innovations will be required, perhaps even innovations in cell chemistry, to meet its targets. Power Electronics and Electrical Systems The electrical and electronic systems technical team has made excellent progress in the last year. The team's program is now well structured, well organized, and well managed. Projects by the national laboratories and Cooperative Automotive Research for Advanced Technologies, as well as projects by the Small Business Innovative Research program, are part of a coordinated program to address technical objectives. Now that an automotive integrated power module has been specified, the results of the Navy's power electronic building block program can be modified to meet the unique requirements of PNGV, as the committee recommended in its fourth report. The committee's concerns that the present cost targets for power electronics and motors may be unrealistic with known and projected technology have yet to be addressed.
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--> Structural Materials Aluminum continues to be the leading candidate material for the Goal 3 vehicles. Efforts are under way to reduce the cost of aluminum sheet through the development of a thin-slab continuous-casting process; during the past year, aluminum sheet produced from direct-cast thin slabs has demonstrated excellent formability characteristics. A program to develop low-cost alloys that do not require heat treatment is also under way. Another accomplishment was the construction of a body-in-white using a combination of carbon fiber-reinforced plastic (CFRP) and aluminum materials, which demonstrated an impressive 68.5 percent weight savings over a baseline steel structure. Although CFRP has impressive possibilities, because of its high cost and long production cycle time, it is still a long-term alternative to aluminum. Manufacturing Processes Significant progress was made in the manufacturing processes for vehicles and specific components, including the optimization of methods for light metal castings; the demonstration of a high-volume programmed powder preform process for producing structural composites; modifications of coatings and designs to improve high-speed drilling processes; the demonstration of compression-molded composite bipolar plates for fuel cells to replace machined graphite plates; and the demonstration of a continuous process for manufacturing fuel-cell membrane-electrode assemblies to replace individual lay-ups. Major Technical and Cost Barriers For the most part, the PNGV's efforts during the past year towards meeting its long-term and short-term objectives have been appropriate and have resulted in very significant achievements. A number of extremely difficult challenges remain, however, which is to be expected with a large, complex development program like the PNGV. These major challenges, which are still significant barriers to the achievement of PNGV's objectives, are discussed below. Emissions Issues and Trade-offs As the committee noted in the third and fourth reports, the most difficult technical challenge facing the CIDI engine program will be meeting the standards for NOx and particulate emissions. (The 4SDI engine team is well aware of this challenge.) In addition, meeting an even more stringent research objective (0.01 g/mile) for particulate matter instead of the 0.04 g/mile PNGV target would require additional technological breakthroughs. Events outside the PNGV, especially the California low-emission vehicle (LEV-2) standards and the
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--> Environmental Protection Agency's (EPA's) anticipated new Tier II proposals, may also affect the commercial viability of advanced vehicles. The committee is concerned that continual changes in standards have placed immense burdens on PNGV's technical development process and its ability to stabilize productive research directions. The capability of the CIDI engine to meet future emissions requirements is uncertain and will undoubtedly require important developments in NOx catalyst technology, particulate trap technology, and power-train sensor and control technology. Fuel composition will also be an important consideration. For example, low-sulfur fuel will improve catalyst efficiency and durability and reduce the amount of particulate mass emitted. Other fuel changes (substantially reduced aromatic content, use of oxygenated organic compounds) may be necessary. The design trade-offs among engine control, the exhaust-gas treatment technology, and fuel will have important implications for cost, fuel economy, and emissions. The gasoline spark-ignited direct-injection (GDI) engine, considered the best short-term backup technology to the CIDI engine, has its own problems with the engine and exhaust-gas treatment emissions technologies, such as trade-offs between fuel economy and the engine design, the cost and effectiveness of the exhaust catalyst system, unresolved questions about particulate emissions, and fuel composition requirements (especially fuel sulfur levels). However, the GDI's potential for achieving the California LEV-2 and EPA Tier II requirements is significantly better than that of the CIDI engine. Unresolved emissions-control issues also relate to fuel-cell technology. When a fuel cell is used with a gasoline or methanol reformer onboard the vehicle, there could be emissions from the reformer, especially during transient operation. The limited data available to date indicate that emissions during steady-state operations can be kept extremely low, but no data exist for transient operating conditions. Fuel sulfur levels must also be kept very low. According to presentations by the PNGV (by government and industry representatives) to the committee, the interdependence of power trains (4SDI engine or fuel cell), fuel economy, and emissions has not being adequately addressed. The current California regulatory proposals on NOx and particulate emissions are likely to preclude the use of the very efficient CIDI engine in the United States unless effective exhaust-gas after-treatment technology can be developed or the emission standards are revised. The successful development of exhaust-gas after-treatment technologies will depend on the extent and rate of implementation of improvements in diesel fuel. To date, the responsible government agencies participating in the PNGV have pursued their specific agency objectives without taking into account the interdependency of these issues. The committee believes the PNGV program represents an opportunity to examine these critical interdependencies and recommends that the PNGV leadership develop appropriate coordinating policies. The technological choices for meeting the PNGV goals
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--> and time frames are limited, and a clear policy on fuel standards, emission regulations, fuel economy, and cost expectations will be essential for meeting them. Cost of Four-Stroke Direct-Injection Hybrid Electric Vehicles With the advanced technologies under development by the PNGV, even if performance targets are eventually met, the costs of vehicles are projected to be much higher than for conventional vehicles. This cost penalty will be exacerbated with an HEV, which is more complex than a non-hybrid vehicle. Thus, the cost reduction involving design, vehicle trade-offs, and manufacturing also remains a significant barrier to the realization of an affordable Goal 3 vehicle. A number of issues have cost implications for a near-term 4SDI-powered vehicle including: emission reductions; a less expensive supply of base materials for the manufacture of reduced-mass body/chassis assemblies, as well as new mass-manufacturing processes; mass reductions in the engine/drivetrain and other components; and improvements in air conditioning, power steering, and other accessories to reduce vehicle mass and meet manufacturability requirements. A successful HEV configuration for the 4SDI engine (or for a fuel-cell vehicle) will also depend on motor and power electronic technologies being reasonably well defined and will require mass manufacturing. The HEV system will also depend heavily on a robust, lightweight, low-cost battery, but battery technologies face significant barriers to meeting cost and performance targets. The lithium-ion system, which appears to be the most promising candidate, will still require the development of mass manufacturing capabilities. Fuel-Cell Cost and Performance Although impressive progress has been made in critical areas, a long list of challenges (and some, undoubtedly, not yet identified) remain to be resolved. The successful demonstration of composite bipolar plates and continuous-process membrane-electrode assemblies will go a long way towards achieving cost goals for fuel-cell stacks. However, the ''multifuel" fuel processor and carbon monoxide cleanup systems are still in the early stages of laboratory development, and potential manufacturing and materials problems have only begun to be identified. The compressor/expander systems are at an intermediate stage of development, but a final product has not been identified, and manufacturing approaches have yet to be defined. The tolerance of the fuel-cell stacks to carbon monoxide and other impurities is still uncertain. The performance of the system of fuel processor, cleanup system, and fuel-cell stack is also uncertain because no working gasoline-fueled systems have been developed, and the systems model is still unverified. Furthermore, no long-term durability tests for major components have been conducted, and only a few high-volume manufacturing processes have been
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--> identified. Consequently, meeting the PNGV targets for fuel-cell cost and performance still presents significant challenges. Fuels Strategy As the committee noted in its fourth report, significant changes in automobile power plants would have wide-ranging effects on the fuels industry. Even if the PNGV program can meet its Goal 3 target with power plants such as the CIDI engine or a fuel cell, marketing the vehicles powered by them may be limited, or even prohibited, by the unavailability of suitable fuels. Therefore, it is vitally important that the PNGV pursue the development of appropriate fuels concurrently. The PNGV recognizes the importance of modified fuel in achieving emission targets for CIDI engines and is testing various fuels. Ad hoc pairings of fuel companies and auto manufacturers have developed test programs to evaluate the effects of various fuels on emissions, as well as on after-treatment catalysts. The U.S. Department of Energy (DOE) has taken the lead in addressing the fuels infrastructure issues, with analyses of the effects of potential changes in fuels and power plants on the infrastructure, cost, energy, and environment. These projections would be more credible if DOE had critical input from the major petroleum companies that would be involved in implementing the changes and could validate the assumptions underlying DOE's projections in practical business terms. EPA should continue to be involved in planning and be made fully aware that if exhaust emission standards are too stringent they could either preclude the use of the most fuel-efficient power plants or require the distribution of a fuel that could not be made available economically or in time to meet PNGV goals. Regular interactions between DOE and EPA might help to elucidate and resolve the necessary trade-offs. Overall, the attention to the fuels issues associated with the PNGV program has increased, but no mechanism has been established to address the fundamental trade-offs between vehicle exhaust emissions and energy efficiency at the government-agency policy level, and long-range strategic issues are not being addressed effectively by the fuels industry or the automobile manufacturers. Cost and Performance of Electrochemical Batteries Meeting the PNGV targets for calendar life and cycle life, but also for specific energy and cost, is in serious jeopardy for both electrochemical battery systems (lithium-ion and nickel metal hydride). Consequently, some national laboratories are being enlisted in a new effort to define generic (nonproprietary) baseline electrochemistry and to show, by example, how to elucidate the failure mechanisms of a system. The development of new electrochemistry is equivalent to starting over. Even though lithium-ion batteries may be preferable in the long
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--> term (year 2004) because of their high efficiency and high specific energy, ongoing problems have revealed that nickel metal hydride batteries should also be made available (and perhaps even advanced lead-acid, nickel-cadmium, or nickel-zinc batteries) for the year 2000 concept vehicles, Achieving adequate calendar life and cycle life, as well as safe abuse tolerance under representative operating conditions and low cost, remain major challenges for PNGV's battery program. The PNGV must put these issues in perspective by (1) developing a better understanding of the factors that control calendar and cycle life, (2) conducting more realistic simulations of likely abuse conditions and their effects, and (3) developing a better understanding of the factors that affect mass-manufacturing costs. Vehicle Systems Analysis The timely application of vehicle systems analysis by the PNGV is critical for making engineering trade-offs and setting the performance and cost priorities for subsystem technologies. The systems analysis team is now qualified to provide analysis and modeling support to all of the technical teams. At this phase of vehicle development, all of the technical teams should be closely aligned with the systems analysis group and using the systems model and associated analytical support services in making their decisions. The committee concluded, however, that this is not the case. Although the second-generation vehicle model has been created, essential validation of PNGV models still remains to be done. The designs of individual concept vehicles by the USCAR partners are proceeding, based on proprietary sophisticated vehicle, subsystem, and component models. Considerable work is being done by government laboratories, suppliers, and academic institutions but is not being guided by validated models. The USCAR partners should find a means of supporting the validation of the PNGV models. The lack of adequate cost models is still a major concern given the magnitude of the projected cost reductions for PNGV vehicles in keeping with the Goal 3 objectives. Without compromising proprietary considerations, cost models should be developed for use by all of the component and subsystem teams. Design decisions by all of the technical teams should be based on these models. Adequacy and Balance of the PNGV Program Once again, the committee finds it difficult to assess the efforts and resources applied to the PNGV program because no funding plan was made available. In several previous reports, the committee concluded that the resources allocated to PNGV activities were incommensurate with the magnitude of the challenges to meet the Goal 3 objectives. The committee is encouraged this time, however, by several trends. First, the number of technologies was winnowed down during the
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--> technology selection process at the end of 1997, allowing PNGV to better focus available resources. Second, the fiscal year 1999 budget for DOE's Office of Advanced Automotive Technologies provided moderate increases for the development of some long-range technologies, like fuel cells. However, these amounts are still far below the level needed to meet the challenges on a timely basis. Third, the three USCAR partners have substantially increased their proprietary efforts towards the development of concept vehicles, and impressive vehicle-development teams have been formed by each car company. Finally, the PNGV technical teams appear to be working well together. Despite these positive developments, the committee believes the PNGV program will need additional resources. Furthermore, it is essential that other government agencies (e.g., EPA) and other industries (e.g., petroleum refiners and automotive component manufacturers) be brought more fully into the PNGV program. The committee believes the near-term and long-term technologies the PNGV has focused on have the potential to meet the program's objectives. Some critics of the program have suggested that the CIDI engine should not be pursued for the U.S. market because of its particulate and nitrogen oxides emissions. However, the committee believes that potential fuel economy and the high degree of technical maturity of the CIDI engine warrant continued development, especially in light of the uncertainties facing fuel-cell technologies. In addition, extensive markets in Europe and Asia for high fuel-economy vehicles offer an opportunity to improve the fuel economy and reduce emissions worldwide. Government Interfaces Seven government agencies are involved in the PNGV program, with the U.S. Department of Commerce playing a lead role. Not all R&D by these agencies is directly relevant to the goals of the PNGV. Some R&D (e.g., R&D in DOE's Office of Advanced Automotive Technologies) is directly relevant to the PNGV and is coordinated with the PNGV technical teams; some is directly relevant but is not coordinated with the PNGV technical teams; and some is only indirectly related to PNGV or supporting long-term research. The seven government agencies also have different missions, and government R&D (either directly or indirectly related to PNGV) takes place in many departments and laboratories. The program office of the U.S. Department of Commerce is doing a commendable job of promoting the interests of PNGV among government organizations and providing workable interfaces in its proactive support of the program. Selected Recommendations The committee has picked a limited number of recommendations to highlight in the Executive Summary. Most of the specific technical recommendations for each subsystem appear in the main body of the report.
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--> Recommendation. The PNGV four-stroke direct-injection technical team should develop projections of the performance of compression-ignition direct injection and gasoline direct-injection power-train systems, especially comparisons of the estimated emissions and fuel economy for each system. These projections would be a first step toward the quantification of trade-offs between emissions and fuel economy based on current and emerging state-of-the-art technologies. Recommendation. The federal government agencies involved in the PNGV program should review how future emissions requirements (especially NOx and particulates), fuel economy, and carbon dioxide emissions, as well as fuel quality, will affect the choice of the compression-ignition direct-injection engine as the most promising short-term combustion engine technology; a program plan that responds to that assessment should be developed. The PNGV, especially the U.S. Department of Energy and the Environmental Protection Agency, should work closely with the California Air Resources Board on these issues. Recommendation. A comprehensive mechanism should be established to help define feasible, timely, and compatible fuel and power-plant modifications to meet the PNGV goals. This mechanism will require extensive cooperation among not only automotive and fuels industry participants at all levels of responsibility, but also among technical and policy experts of the relevant government organizations. Recommendation. The PNGV should conduct life-cost and performance-cost trade-off studies, as well as materials and manufacturing cost analyses, to determine which battery technology offers the best prospects and most attractive compromises for meeting capital and life-cycle cost targets. Recommendation. Without compromising proprietary information of the USCAR partners, the PNGV should conduct in-depth cost analyses and use the results to guide subsystem and vehicle affordability studies.
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