This is the seventh 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 (GM). The program addresses improvements in national competitiveness in manufacturing and in the implementation of energy-saving innovations in passenger vehicles. In addition, it seeks to develop a new generation of vehicles by setting a stretch goal to achieve fuel economy up to three times (80 miles per gallon [mpg] gasoline equivalent) that of comparable 1994 family sedans without sacrificing size or utility or increasing the cost of ownership. The purpose of this program is to conceive, develop, and implement new technologies capable of significantly reducing the petroleum consumption and carbon dioxide emissions of the U.S. automobile fleet. The founders recognized that, to have substantial impact, this new generation of vehicles must be sold in high volume. This, in turn, requires that the vehicles meet or exceed all emission and safety requirements and offer all of the characteristics that result in strong customer appeal.
This report contains the committee's assessment of the overall balance and adequacy of the PNGV research program to meet its technical goals and the program's efforts to develop commercially feasible low-emission propulsion systems. The committee also comments on significant changes that have occurred since the inception of the PNGV program and how these changes might influence this program.
PROGRESS AND MAJOR ACHIEVEMENTS
The PNGV program has overcome many challenges and has forged a useful and productive partnership of industry and government participants. In addition to the cooperative program, substantial proprietary industry R&D activity has been generated. Teams of industry and government representatives have addressed formidable technical issues and made significant progress on many of them despite the complexity of managing an inter-disciplinary program involving three competing companies, several government agencies, and significant government budget constraints. The program concept cars introduced in January and February of 2000 are important evidence of these activities, but the ongoing R&D program, much of which is summarized in the following sections, is equally significant.
The following summarizes activities for meeting goals 1, 2, and 3 of the program.
The manufacturing competitiveness goal, Goal 1, addresses the need to develop improved manufacturing processes for conventional vehicles, as well as the new-generation vehicles and their components. A wide array of manufacturing issues has been addressed in the cooperative program. Projects to reduce the cost and improve the quality of aluminum structures, drill holes more rapidly, and improve leak testing were completed in 2000–2001. Several projects to facilitate the manufacture of lower-cost, lighter-weight vehicle bodies have been proposed for funding in fiscal year 2002. Manufacturing considerations are being addressed for many of the new components that will be required by the radically different hybrid-electric-vehicle power trains being developed. Also, several longer-term and higher-risk manufacturing projects are at the proposal stage.
Since a large proportion of the components needed to assemble automobiles comes from suppliers, the need for manufacturing improvements extends well beyond the automobile manufacturers themselves. Suppliers are already involved in some PNGV activities, but the PNGV manufacturing program would benefit from expansion of these supplier activities.
The purpose of Goal 2 is to speed the introduction of new technology generated by PNGV R&D into production vehicles. Several manufacturing and engineering analysis tools developed by the program are in use, and significant applications of lightweight materials have been introduced in production vehicles.
The most striking Goal 2 achievement is the announced plans by all three automobile companies to introduce hybrid power trains during the next two to three years in both pickup trucks and sport utility vehicles in a variety of configu
rations. The reduction in fuel consumption will range from 10 to 30 percent, twice the amount that would be saved if the same percentage reduction were obtained by applying hybrid technology to a mid-size car that initially had two times the fuel economy (mpg) of these trucks. The committee commends the automobile companies for this commitment to produce vehicles that will significantly reduce the total fuel consumption of the light-duty vehicle fleet even with an increase in sales.
Goal 3 has provided an extremely challenging focus for the program: to develop within 10 years (by 2004) vehicles that will achieve up to three times the fuel efficiency of comparable 1994 family sedans while retaining the features that make them marketable and affordable. The year 2000 concept-vehicle milestone was met when the three manufacturers each introduced concept cars: the DaimlerChrysler ESX3, the Ford Prodigy, and the General Motors Precept, as detailed in the last committee report. All three concept vehicles incorporate hybrid-electric power trains designed around small, turbocharged, compression-ignition direct-injection (CIDI) engines, using diesel fuel, which shut down when the vehicles come to rest. All employed the significant technical advances developed in the PNGV program to reduce the energy requirements for propelling the vehicle (e.g., reduced mass, aerodynamic drag) and for supplying auxiliary loads (e.g., heating, air conditioning). Each company took a different approach to the design of these cars, which resulted in different remaining challenges to meet the fuel economy and affordability targets, but all of the cars operate on diesel fuel. These cars provide a valuable measure of how challenging it will be to meet all the components of Goal 3 simultaneously.
The next major Goal 3 milestone of the PNGV program as currently structured is the development of production-prototype cars by 2004. Each car company is in the planning stage for this activity, and the approach that each may take is not clear. Validation of production readiness for a new car requires immense resources compared to the preceding R&D activities. For these resources to be justified, the car must be one that is included in the production plans of each manufacturer, plans that are, of course, proprietary. In order for the committee to evaluate the PNGV program in context, each year the car companies have shared proprietary information with the committee. As work progresses toward production prototypes, more of it becomes proprietary and this limits the detail about Goal 3 activity that can be reported by the committee in this and future reports.
Vehicle Engineering, Structural Materials, and Safety
The PNGV concept vehicles made public last year all made extensive use of lightweight materials and new body construction techniques to achieve major
reductions (20 to 31 percent) in curb weight. The high cost of these lightweight materials and the associated manufacturing costs represent a significant part of the affordability challenge faced by the program. More than 30 materials projects have been established to attack the technical challenges identified. In addition, the car companies each have proprietary programs, and the American Iron and Steel Institute has embarked on a second-phase advanced vehicle concept car aimed at identifying affordable ways to reduce weight.
As progress is made on these projects the benefits of lighter-weight construction will be achieved in production vehicles. The PNGV program has developed lower-cost, lightweight-material production processes such as continuous casting of aluminum sheet, powder-metal processes for aluminum-metal matrix composites, and a microwave process for producing carbon fiber. Vehicle production programs using these materials probably will be necessary to provide material suppliers with the incentive to invest in these new processes.
The newly formed PNGV Safety Working Group is addressing safety issues that have been raised by the concept-car designs. The crashworthiness of lighter-weight vehicles in car-to-car accidents is an issue being studied. While the stated goal is to meet present and future Federal Motor Vehicle Safety Standards, it is recognized that these are minimum standards. The purpose of the Safety Working Group is to identify and sponsor research directed at the unique safety characteristics of PNGV vehicles in order to help ensure the marketability of vehicles employing these new technologies.
Four-Stroke Direct-Injection Engines and Fuels
The CIDI engine operating on diesel fuel, chosen for its high efficiency, continues to be the major focus of PNGV power-plant development for near-term application. Current PNGV activity centers on the challenge of meeting new emission standards and is being pursued in engine combustion, exhaust-gas after-treatment, and fuels development programs. Aggressive emission reduction targets have been set for the program to meet through the year 2007. As noted in last year's report (NRC 2000), these emission targets, driven by the newly promulgated Tier 2 emission standards, are now much more stringent than they were at the outset of the PNGV program.
In the combustion program, diagnostic techniques for measuring cylinder-to-cylinder distribution of recirculated exhaust gas (a key NO x control measure) and for in-cylinder measurement of particulate particle size and number have made progress this year. Advanced simulation techniques have also been developed and validated, with the promise of these techniques becoming useful as an optimizing tool for engine design.
NO x exhaust-gas after-treatment is being pursued using lean-NO x absorber catalysts, selective catalytic reduction systems using urea, and nonthermal plasma catalytic systems. Development is in an early stage, and all systems result in a
fuel economy penalty, some estimated as low as 0.5 percent and others as high as 8 percent. Nitrogen oxide traps also are being tested with the current conclusion that, because of extreme sensitivity to sulfur poisoning, they may require simultaneous use of a sulfur trap. Particulate reduction will require yet another trap and an effective regeneration mechanism.
The engine-fuel interactions program was focused on the effects of fuel chemistry and physical properties on engine performance and emissions. Results to date indicate that the fuel does have an effect on engine-out particulate and NO x emissions, but that these effects are not large enough to eliminate the need for substantial after-treatment. The sulfur level in fuels will have a significant effect on both engine-out particulates and the performance of after-treatment systems. Quantification of these relationships remains a priority.
Fuel cells continue to show promise of high efficiency and very low emissions with continuous progress toward targets that are very difficult to meet for any general-purpose, high-volume automotive application. There are many substantial barriers remaining to be overcome prior to the realization of a mass-manufactured consumer vehicle. These barriers include performance as well as physical, fuel-related, and cost issues. In the short term it appears that some limited-production fleet vehicles will operate on pure hydrogen stored onboard the vehicle, which results in a simpler and less expensive system for the vehicle; however, for the foreseeable future, high-volume, general-purpose vehicles likely will require the fuel cell system to be combined with an onboard reformer that produces hydrogen from a liquid fuel. The efficiency of these liquid-fuel reformers is a critical issue: Current prototype reformers significantly degrade the overall fuel cell system efficiency.
This year a major program milestone was the demonstration of two integrated gasoline-fueled 50-kW fuel cell systems. The projected size, weight, and cost of these systems are short of the original year 2000 targets by a large margin, but these systems represent encouraging progress and will help define the goals for component development that will improve system performance. Significant improvements have been demonstrated in many of the components: fuel processors, heat exchangers, catalysts, bipolar plates, and complete stacks. In addition, large proprietary programs are under way both by the automobile companies and potential fuel cell suppliers, and these programs are driving component improvements in all of these areas.
Research and development on batteries continues to focus on nickel metal hydride, lithium-ion, and more recently, lithium-polymer designs. Full-scale sys
tems employing each of these designs have demonstrated their capability to meet the key technical performance targets for hybrid-vehicle applications during the past year, but the battery life challenge has become even more severe. The technical team has adopted targets that correspond to a 15-year battery calendar and operating life. The battery cost targets seem to be very aggressive. The costs of batteries in the currently marketed Japanese hybrid vehicles exceed these PNGV targets by a factor of five or more. These targets should be re-examined in the context of the prospects for meeting cost targets for the other key hybrid-vehicle subsystems.
Supporting basic research has helped define fundamental failure mechanisms of lithium-ion cells and the cause of thermal runaway. New cells have shown life improvement in elevated-temperature accelerated tests, and more realistic calendar life testing methods are being developed.
Power Electronics and Electrical Systems
Both the power electronics and electric motor programs are focused on reducing the cost of these components. Three contractors for the power electronics module have each executed a detailed economic gap analysis with their suppliers to identify ways to ensure that their cost target can be met. These analyses have provided detailed plans for material, labor, and overhead cost reductions, and these plans provide reasonable confidence that the goals can be met. One of the electric motor contractors is pursuing an axial gap permanent-magnet motor design, and the other is using a more conventional radial gap induction machine.
Research programs at the national laboratories and at universities continue to develop promising technologies for essential electronic and motor materials and components. These include silicon-carbide-power semiconductors, carbon-foam thermal materials, high-energy magnets, and low-cost, high-dielectric-constant materials for capacitors.
As noted, significant progress continues to be made by the research being performed in the PNGV partnership and in the many proprietary programs being carried out by the individual partners in USCAR. Nevertheless, the committee believes it is unlikely that all of the elements of Goal 3, including three-times fuel economy, will be met in production-prototype vehicles in 2004. While the bulk of the requirements (e.g., performance, comfort, cargo space, utility, and safety) can be met, the combination of 80 mpg and affordability appears out of reach. In addition, the recently promulgated Environmental Protection Agency (EPA) Tier 2 emission requirements will require radically better emission control technology. It also appears that the required after-treatment devices may significantly degrade the efficiency of the CIDI engine and increase its cost. Fuel issues also
pose significant questions that affect the viability of widespread automobile use of the CIDI engine and, longer term, of fuel cells, which require a supply of hydrogen or a fuel that can be converted to hydrogen.
High prospective cost is a serious problem in almost every area of the PNGV program. Lightweight body construction, CIDI engines, batteries, and electronic control systems all represent increases in vehicle cost. Needed emission exhaust-gas after-treatment devices are not well defined at this point, but they will most certainly be more expensive than systems currently employed. The major effort to date has been to achieve the technical targets for these components, and the concept cars demonstrate the significant progress made; however, none of these cars in their present forms represents an affordable set of components compatible with similar mission vehicles.
Cost targets have always been in place for the major components, but it has not been clear to the committee that even if these targets were achieved an affordable vehicle would result. This year a new cost-modeling effort has been started to address this vital subject. The plan is to develop a tool that will help the technical teams direct their pre-competitive R&D efforts and help suppliers find ways to reduce the gap between current costs and those needed to get to production feasibility. The committee compliments the PNGV for getting this effort under way.
As noted earlier, affordability is the linchpin of the PNGV program. For the benefits PNGV intended to be realized, the economics must favor large-scale purchases of these vehicles.
Exhaust Emissions Trade-off
The last committee report (NRC, 2000) noted that the Tier 2 NO x and particulate matter (PM) emission standards could preclude the early introduction and widespread use in the United States of CIDI engines for passenger cars. Without the CIDI engine the fuel economy of near-term PNGV cars could drop by as much as 25 percent, the approximate difference in fuel economy between a CIDI and a homogeneous-charge, spark-ignition engine. Although, as detailed later in this report, significant progress is being made in developing exhaust after-treatment systems for CIDI engines, these devices make this power plant less attractive by increasing its fuel consumption and cost. Alternative power plants that can meet the Tier 2 emission standards will, in all likelihood, have substantially higher fuel consumption and carbon dioxide emissions. This raises the obvious policy question of the relative importance to the nation of decreasing fuel consumption and carbon dioxide emissions compared with the need to tighten the NO x and PM standards at this time. This trade-off was noted in the last committee report, but
the committee is unaware of any subsequent substantive discussion of the issue. Its resolution has obvious implications for the PNGV production-prototype planning process that is now under way.
Historically, major improvements in automobile power-plant efficiency and exhaust emissions have required changes in the fuels they use. Notable examples are the high-octane fuel that was required by high-compression-ratio engines and the unleaded fuel required by catalytic converters. Both the CIDI engine and fuel cells being considered by the PNGV are no exception. Successful introduction of either new power plant will be critically dependent on widespread availability of suitable fuels.
The large capital expenditures and long lead time required to manufacture and distribute a significantly modified fuel means that the petroleum industry must be fully aware of the needs well in advance of the production of the first automobile that requires such a fuel. Furthermore, the change must make economic sense for the petroleum companies or be mandated by regulation. In early 2001, the EPA published a regulation requiring refiners to produce highway diesel fuel with a maximum sulfur content of 15 ppm by June 1, 2006 (Federal Register, 2001). This regulation gives the PNGV CIDI development program the challenge of finding an exhaust after-treatment system that will perform and endure with such a fuel, since it is unlikely that fuel with any lower sulfur level will be available in this time frame.
Automotive fuel cell power plants present a much more complicated problem because of the early development stage of these systems. The most efficient and lowest-emission system involves direct hydrogen storage on the vehicle, which requires major infrastructure changes by the energy industry. With a reformer onboard the car, a liquid fuel can be used, and it is hoped that one similar to gasoline will be satisfactory. In the long term, reformers probably will require a fuel tailored for this application to achieve optimum efficiency and minimum emissions.
From this discussion it is clear that a strong, objective, cooperative program between the PNGV participants and the petroleum industry is needed to ensure that the lack of appropriate fuels does not become a major barrier to realizing the goals of the program. It appears that additional priority will be required to advance this goal, as there has been little apparent progress in this area since the committee made a similar recommendation last year.
From the inception of PNGV, practical automotive fuel cell power plants have been considered to be well beyond the 2004 time limit of the program.
Nevertheless, because of their potential for high energy efficiency and no onboard emissions of any regulated pollutants when using hydrogen as a fuel, the development of these systems has remained a major part of PNGV. As noted above, progress has been steady, and some important milestones have been met. Nevertheless, the original targets for 2000 for the fuel cell system were not met. At present, it appears that the dates for meeting these targets should be extended substantially. Size and weight need to be reduced by at least a factor of two to meet the 2004 targets, and cost is roughly six times above the target value for a 2004 PNGV-type vehicle. Even with these formidable challenges, based on projections from the major auto manufacturers it appears that some limited-application fuel-cell-powered vehicles may be produced in the 2003–2005 time frame. Even ignoring cost, these vehicles will likely not be suitable for sale to the general public. It is expected that they will operate with onboard hydrogen storage systems and therefore be restricted to fleet use, where limited range and complex refueling issues can be managed.
Large investments are being made in the commercial development of fuel cell power plants for stationary and nonpropulsion mobile applications. These applications are likely to become successful well before the more stringent cost, size, and weight requirements for an automobile power plant can be met. Some of the extensive R&D being performed for these commercial applications and manufacturing experience with them may help the development of a practical automotive system, but the R&D needed to address the requirements of a vehicle power plant is unique. The PNGV program and extensive proprietary work in the car companies are meeting this need.
ADEQUACY AND BALANCE OF THE PNGV PROGRAM
The adequacy and balance of the PNGV R&D program are difficult to assess. Goals 1 and 2 are stated in qualitative terms, and, as noted previously, 80-mpg production prototypes meeting Goal 3 requirements are not likely to be realized in 2004. The last committee report (NRC, 2000) contained an extensive discussion of this subject, including at least three definitions of success that the existing goals allow:
The committee believes that no reasonable amount of funding would ensure achievement of all aspects of Goal 3, including 80 mpg, the first definition of
success, and that has been clear for some time. Breakthrough ideas and talented people are more stringent constraints than money to achieving this goal. Current activities appear to be directed toward the latter two definitions of success; however, no clearly stated objectives have been enunciated by the PNGV. This deficiency needs to be corrected before a meaningful external assessment of the adequacy and balance of the program can be made.
Government funding for the program comes primarily from the U.S. Department of Energy (DOE) advanced automotive technology budget. For fiscal year 2002 this amount was initially proposed to be about $147 million, an increase of about 10 percent from the previous year. At the time of this report the budget process was still under way, but a substantial cut to $100 million has been proposed in the President's budget for the DOE PNGV funding. Other funds identified as supporting the PNGV total about $87 million: in the budgets of the EPA ($27 million), the Department of Commerce ($15 million), and the National Science Foundation ($47 million). Of these latter amounts about three-quarters are only indirectly associated with the program, not directly coordinated with the efforts of the technical teams. The balance of the programs directly coordinated by the technical teams appears to be appropriately weighted toward solving long-range research problems.
Industry funding for “PNGV-related” research has been previously reported to be over $980 million per year for four years of the program, far higher than the 50/50 government-industry matching common in many cooperative programs. A major portion of this funding is in proprietary product programs, the details of which are unavailable to the committee. Furthermore, as the program moves more toward the application of technology to production vehicles, determining the appropriate portion of overall company R&D expenditures that should be associated with the PNGV becomes highly subjective.
THE FUTURE OF THE PNGV
The committee believes that the PNGV program has established a unique and a valuable framework for directing closely coordinated industry and government research efforts toward the development of technologies capable of solving important societal problems. These efforts have resulted in a number of significant technical successes to date. It appears, however, that the current context of the partnership is sufficiently different from that in 1993 to warrant a reconsideration of its specific goals.
The issues addressed by the program are still relevant. The need to reduce the fuel consumption and carbon dioxide emissions of the U.S. automotive fleet is more urgent than ever. Since 1993 there has been a 20 percent increase in the petroleum used in highway transportation, the percentage of U.S. petroleum use derived from imports has risen to 52 percent, and in many parts of the world
concerns about the potential for climate change associated with greenhouse gases are even more acute.
On the other hand, during this time, the demand for sport utility vehicles, vans, and pickup trucks in the United States has drastically increased to the point that they now make up 46 percent of new light-duty vehicle sales. This has increased the importance of reducing the fuel consumption of these vehicles compared to that of the typical family sedan. The EPA Tier 2 emission standards in all likelihood will increase the fuel consumption of all new cars and threaten to preclude the widespread introduction of the more efficient diesel engine in lightduty vehicles. Lastly, the changed global structure of the industry has made it much more difficult to make sense of the U.S. competitiveness statement in Goal 1.
In view of these facts and as a new energy policy is being developed for the nation, it is the committee's belief that the priorities and specific goals of the PNGV program should be reexamined. There is a need to update the program goals and technical targets in the context of current and prospective markets. The program would also benefit from a better mechanism that will provide more of a systems approach to identifying issues, planning for issue resolution, and tracking process. The PNGV governance structure contains an Operational Steering Group with high-level representation from both the industry and each of the participating agencies. This provides an opportunity to develop policy trade-offs to ensure that the best interests of the nation are served in economics, the environment, national security, and mobility—an opportunity yet to be realized in any significant way.
Recommendation. Taking into consideration the successes, degree of progress, and lessons learned in the PNGV program to date, government and industry participants should refine the PNGV charter and goals to better reflect current societal needs and the ability of a cooperative, precompetitive R&D program to address these needs successfully.
Recommendation. The PNGV should continue the aggressive pursuit and development of lean-combustion exhaust-gas after-treatment systems. The PNGV should also work to develop a detailed systems-modeling effort to quantify the fuel economy penalty associated with using different technologies to meet the emission standards. These efforts should include quantification of the extent to which vehicle hybridization can be used to reduce emissions and the fuel consumption impact of changing the vehicle's primary energy converter.
Recommendation. Because of the potential for near-zero tailpipe emissions and high energy efficiency of the fuel cell, the PNGV should continue research and development efforts on fuel cells even though achievement of performance and cost targets will have to be extended substantially beyond original expectations.
Recommendation. Because affordability is a key requirement of the 2004 production-prototype vehicles, the committee believes that more attention should be paid to the design and manufacturing techniques being worked on by the American Iron and Steel Institute in the Ultralight Steel Auto Body Advanced Vehicle Concept project. These techniques should be applied to aluminum-intensive vehicles, as well as hybrid-material body construction. More broadly, the committee urges a systematic, critical examination of the prospects to achieve cost goals for all key vehicle subsystems and components.
Recommendation. High priority should be given to determining what fuel sulfur level will permit the preferred compression-ignition direct-injection (CIDI) engine and its after-treatment system to meet all regulatory and warranty requirements. An enhanced cooperative effort between the auto and petroleum industries should be undertaken to ensure that the fuels needed commercially will be available on a timely basis.