This is the sixth 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). A major objective of the PNGV program, referred to as the Goal 3 objective,1 is to develop technologies for a new generation of vehicles with fuel economies up to three times (80 miles per gallon [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 must 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.
In this report, the committee continues to examine the overall adequacy and balance of the PNGV research program to meet the program goals and requirements (i.e., technical objectives, schedules, and rates of progress). The committee also discusses ongoing research on fuels, propulsion engines, and emission controls to meet emission requirements and reviews the USCAR partners’ progress on PNGV concept vehicles for 2000.
PROGRESS AND MAJOR ACHIEVEMENTS
Considering the magnitude of the challenges facing the program, PNGV is making good progress. As the program has evolved, the PNGV technical teams have become more effective and have developed good working relationships. In addition, the USCAR partners have created substantial vehicle engineering teams devoted to the development of the concept vehicles, which were unveiled in January and February 2000. PNGV has also responded positively to most of the committee’s recommendations in the fifth report. In general, the committee congratulates the PNGV partners on their progress in the past year.
Concept Vehicle Milestone
The PNGV has met its 2000 concept vehicle schedule and milestone with the unveiling, in January and February 2000, of the USCAR partners’ concept vehicles (DaimlerChrysler’s ESX3, Ford’s Prodigy, and GM’s Precept). Meeting this milestone represents an outstanding industry effort. The concept vehicles are intended to establish the functional benefits of their designs but may include components for which validated manufacturing processes and affordable costs have not yet been demonstrated. As expected, each manufacturer has taken a somewhat different approach, but the concept cars all share technology and know-how developed in PNGV, some of which is finding its way into current production vehicles (as called for in Goal 2).
All of the concept vehicles incorporate hybrid-electric drive trains designed around small, turbocharged, compression-ignition, direct-injection (CIDI or diesel) engines that shut down when the vehicles come to rest. These hybrid electric vehicles (HEVs) have been constructed according to sophisticated structural optimization techniques with high strength-to-weight materials, such as aluminum and composites, in both bodies and interiors. Every aspect of these cars, including wheels, tires, interior components, front, back, and side windows, rear vision devices, and aerodynamic drag, has been designed to reduce weight and increase efficiency. Friction has been reduced in almost every rotating component. All three cars are expected to achieve 70–80 mpg (gasoline equivalent), the ESX3 at 72 mpg, the Prodigy at 70 mpg, and the Precept at 80 mpg, although tests have not been run to confirm these figures. Emissions are targeted at the Environmental Protection Agency’s (EPA’s) Tier 2 standards, but the after-treatment systems required to achieve these standards have not been defined.
In summary, the concept cars represent a major milestone toward meeting the PNGV Goal 3, and each contributes significantly to our understanding of the challenges this goal represents. In addition, GM has built a fuel-cell version of the Precept, which is packaged in the same basic chassis and body and includes a hydride hydrogen storage system. The fuel-cell Precept is expected to achieve a gasoline-equivalent fuel economy of more than 100 mpg when supplied with hydrogen. A fully functional version of this car is expected by the end of 2000.
The automotive companies have taken different approaches to meeting Goal 3. For example, the Ford Prodigy power train system is considerably simpler than the power train in the GM Precept. Thus, the Ford system is closer to meeting the affordability target of Goal 3 but sacrifices some fuel economy by limiting the amount of potential regenerative braking. The DaimlerChrysler ESX3 has large injection-molded plastic body sections, which have the potential for building a body structure that both weighs less (the ESX3 curb weight is lower than that of the Precept or the Prodigy) and costs less than conventional steel bodies and is completely recyclable. The aluminum body construction used for the Ford Prodigy and the GM Precept currently costs significantly more than a comparable steel body, but as fabrication of aluminum bodies improves, they may become competitive with steel.
Goals 1 and 2
Although most of the discussion in this report about achievements and barriers is focused on Goal 3, continuing and significant progress has also been made toward achieving goals 1 and 2. For example, a project has been successfully completed demonstrating continuous cast sheets of Series 5000 aluminum for body structures, and a follow-up project to develop similar processes for exterior body parts is under way. Several smaller efforts to expand aluminum manufacturing and assembly capabilities are in progress, and an alliance between the automotive and aluminum industries has been formed to address standardization, scrap recovery, and other issues. Cost reductions, improved properties, and new manufacturing techniques for carbon-fiber composites, as well as the recycling and design of hybrid material bodies, have also been achieved. Aluminum springback predictability techniques have also been developed.
Goal 3 Achievements
Substantial technical progress has been made in reducing the energy requirements for propelling the vehicle (e.g., reduced mass, drag, etc.) and for supplying auxiliary loads (e.g., heating, air conditioning, etc.). Continual improvements have been made in the efficiency and performance of power plants (four-stroke direct-injection engines, fuel cells [as a long-range technology]), energy storage (batteries) for HEVs, and the development of modeling and simulation techniques. The three concept vehicles represent the results to date of these substantial efforts by the USCAR partners.
Vehicle Engineering and Structural Materials
A number of accomplishments have been made in vehicle engineering, including the fabrication and testing of a lightweight, hybrid-material body to
validate a weight reduction of more than 40 percent; the completion of an energy-efficient, occupant comfort project with a 75-percent reduction in required energy; and the completion of a lightweight interior project demonstrating a 157-pound reduction in interior weight. In addition, projects have been initiated or continued on a high (42 percent) payload/curb-weight ratio, low rolling resistance (run-flat) tire, underbody airflow management, and energy-efficient side windows.
The committee believes that, as the PNGV program moves toward the development of 2004 production-prototype vehicles, affordability will be a key requirement. PNGV should closely monitor the development of an efficiently designed and fabricated steel-intensive vehicle being developed by the Ultralight Steel Auto Body Consortium (which is not part of PNGV), including the possibility of a hybrid steel-aluminum vehicle. In addition to continuous casting of aluminum sheet, PNGV has also made progress in developing lower cost aluminum and magnesium casting processes, lower cost powder-metal processes for aluminum-metal matrix composites, and a microwave process for lower cost carbon fiber.
Four-Stroke Direct-Injection Engines and Fuels
A number of new collaborative projects in advanced combustion and emission controls have been initiated; other projects are continuing to advance the understanding of catalysis, as well as to define fuels issues. New catalysts have been developed: a catalyst with lower “light-off” temperature and better nitrogen oxides (NOx) reduction; a zeolite-supported catalyst to improve NOx reduction; and microporous catalysts that show promising results.
Other projects are exploring novel means of reducing emissions of particulate matter (PM), improving the effectiveness of exhaust gas recirculation, and gaining a better understanding of combustion processes. A PM filter has been developed that has the potential to remove up to 90 percent of diesel particulates and can be regenerated at idle using microwave heating techniques. In addition, a plasma-assisted catalyst has been developed that shows high NOx conversion rates even in the presence of sulfur.
It has also been demonstrated that changes in fuel formulation could reduce diesel PM emissions by 50 percent and NOx emissions by 10 percent. Refinery models are being used to evaluate the effects of various formulations on diesel fuel costs and to define other issues related to fuels infrastructure.
Both national laboratories and industry contractors have made notable accomplishments on fuel cells. A gasoline (fuel-flexible) fuel processor has been operated in conjunction with a 10-kW proton exchange membrane (PEM) stack, but not as an integrated system. Microchannel fuel processing of iso-octane has been demonstrated and a new higher temperature nonair-sensitive fuel processing catalyst has
been developed. A fuel anode that is much more tolerant to carbon monoxide has been demonstrated and a high power density fuel cell stack, low-cost composite bipolar plates, and low-cost membrane electrode assemblies have all been demonstrated by industry. Improvements in modeling and simulation are continuing, and production techniques for low-cost molded bipolar plates have been demonstrated.
Research and development on batteries have been focused primarily on nickel metal hydride, lithium-ion, and lithium-polymer batteries because of their potential for high power-to-weight ratios for HEV applications, and (at least in some cases) low cost. During the past year, PNGV has received and evaluated a 50-V nickel metal hydride battery module and has received four lithium-ion battery modules for testing. The development of a 300-V battery system has been initiated. Lithium-ion electrochemistries projected to increase calendar life from two years to three to five years have been identified. Failure mechanisms and abuse tolerance issues for lithium-ion systems are better understood. However, projected costs are three times higher than the PNGV goals.
Nickel metal hydride batteries were used in Ford’s Prodigy concept vehicle; lithium-ion batteries were used in DaimlerChrysler’s ESX3 concept vehicle; and nickel metal hydride (and later lithium polymer) batteries were used in GM’s Precept concept vehicle.
Power Electronics and Electrical Systems
The committee compliments PNGV’s comprehensive power electronics and electrical systems program for its excellent organization and management. The program has accomplished a good deal in the past year. For example, improved direct-current power bus capacitors suggest that improved performance and reduced cost are feasible. An ongoing project is helping to assess the mechanical reliability of electronic ceramic devices and less expensive alternatives through mechanical characterization. Processes to fabricate neodymium-iron permanent magnets with up to 25 percent higher strength than current magnets are being developed, and a facility has been completed and work initiated on characterization of the magnets. In addition, a 100-kW inverter with a power density of 11 kW/kg has been developed, and collaborative efforts are under way on a lower cost 100-kW motor controller.
In spite of substantial accomplishments in virtually every technical area of the PNGV program, formidable barriers remain to be overcome. The realization
of an advanced high fuel economy vehicle that meets Goal 3 requirements and is acceptable in the marketplace still faces significant barriers of cost, emissions, and fuel infrastructure. New business arrangements, such as the Daimler-Chrysler merger and the Delphi spinoff from GM, as well as the fact that the program has moved into the production prototype development stage, have complicated reaching a consensus on precompetitive projects.
As the committee has noted in previous reviews, vehicles incorporating both near-term and long-term technologies face critical cost barriers. In the committee’s opinion, meeting the three most critical requirements (emissions, fuel economy, and cost) of Goal 3 by 2004 is very unlikely. Although 80-mpg fuel economy appears to be technically feasible, the cost requirement is clearly unattainable. The Tier 2 emissions standard appears to be attainable only with a fuel economy well below 80 mpg, and, even then, will be difficult to achieve in production vehicles with adequate probability for meeting the certification period of 100,000 miles. The development of vehicles of radical design (e.g., a fuel-cell vehicle) for mass production that meets all of the Goal 3 objectives by 2004 is also highly optimistic.
High cost is a serious problem in almost every area of the PNGV program, and the costs of most components are higher than their target values. For example, neither aluminum nor composite materials are yet projected to reach costs competitive with steel for most major vehicle components; the CIDI engine will require low-cost after-treatment and cost reduction for common-rail fuel injection; battery costs are still projected to be at least three times target costs; projected costs for fuel-cell systems are still at least five times the long-term targets; low-cost manufacturing techniques have yet to be developed for power electronics; and integrated thermal management for power electronics is still complex and costly. As far as the committee is aware, detailed cost analyses for overall vehicle systems have not even been attempted yet by some of the automotive companies, but rudimentary estimates for complete vehicle systems show cost penalties of several thousand dollars. In fact, DaimlerChrysler has estimated a $7,500 selling price cost penalty for a production version of its ESX3 concept vehicle.
As the committee has stated in previous reviews, the cost penalty is exacerbated with an HEV, which is more complex than a nonhybrid vehicle. If the federal administration and Congress want to promote the deployment of high fuel economy PNGV-type vehicles, they may have to evaluate the advisability of providing temporary incentives (e.g., tax rebates) to offset higher initial vehicle costs.
Impact of Emission Standards
The Tier 2 NOx and PM emission standards announced at the end of 1999 are significantly more stringent than the standards in place when the PNGV program was initiated. Based on several presentations, including two by EPA, the feasibility of meeting these standards with acceptable fuel economy in the time frame of the PNGV program is very questionable. Meeting the Tier 2 standard for diesel engines will likely require new catalytic materials and new emissions control concepts. In the committee’s judgment, the Tier 2 standards as currently promulgated could potentially preclude the early introduction of the CIDI internal combustion engine with its significant fuel economy benefit in the United States or, as a result of compromises to meet the Tier 2 standards, reduce the CIDI engine fuel economy benefit. To meet new standards, PNGV may have to shift its attention from the CIDI engine toward the adaptation of other internal combustion engines with better potential for extremely low emissions but at lower energy conversion efficiencies and with higher carbon dioxide emissions. The change in emission standards will affect the PNGV program in a variety of ways, which are discussed throughout the report.
The introduction of Tier 2 standards raises questions that should be discussed by USCAR and government agencies involved in the PNGV, namely whether the reduced fuel economy that would be provided by the alternative engines available for the next phase of the program (i.e., the 4SDI [four-stroke direct-injection] spark-ignition engine and the port fuel-injected gasoline spark-ignition engine), which have significantly better potential for meeting the Tier 2 emission levels, is an appropriate trade-off from a national perspective. A wiser decision might be to extend the deadline for meeting these two objectives—improved fuel economy and lower emissions—allowing more time for the development of new fuel economy technology. This issue will have to be resolved before PNGV can clarify the objectives of the production-prototype phase of the program.
Although modern in-cylinder injection, high rail pressures, and closed-loop control can dramatically reduce emissions from CIDI engines, the new Tier 2 standards are not likely to be met with currently available high-sulfur diesel fuel, even with PM traps and NOx absorbers. For fuel-cell vehicles, onboard reforming of gasoline to produce hydrogen would probably require substantial changes in gasoline composition; in fact, optimum performance would probably require a new hydrocarbon fuel very different from conventional gasoline. In addition, because of the negative impact of sulfur on catalysts, sulfur concentrations in all petroleum fuels would have to be reduced substantially. As the committee has pointed out in previous reports, significant changes in fuels would also have
wide-ranging effects on the petroleum and fuels industry, infrastructure, and costs. Therefore, changes in fuels must be carefully planned and their implications thoroughly investigated.
The PNGV program has been devoting more attention to fuel composition issues and is working with individual petroleum companies but has not established a mechanism to determine the commercial trade-offs between engine systems (with the attendant effects on fuel economy) and fuel compositions. Greater participation by the petroleum and fuels industries will be critical to the success of the PNGV program.
Up to now, PNGV has given a high priority to automotive systems that can achieve the goals of the program. The committee agrees that this was the correct approach for the beginning stages of the program. Now, however, fuel issues must be addressed strategically, in cooperation with the petroleum industry. Otherwise, commercialization of the technologies being developed could be delayed because of the lead time required to manufacture and distribute modified fuels.
Since the beginning of the PNGV program, the fuel-cell energy converter has shown the potential to provide high fuel economy and produce very low emissions. Despite the significant progress that has been made and the substantial private sector resources that have been expended, the committee continues to consider fuel cells a long-range technology applicable to automobiles beyond 2004 because of the outstanding technical and cost issues. However, because the Tier 2 standards have increased the development risk for the CIDI engine, the fuel cell has been elevated to a higher level of importance, and PNGV has been focusing its efforts on processing (reforming) gasoline on board the vehicle to produce hydrogen, which would sidestep the fuels infrastructure problem of the lack of widespread availability of hydrogen. However, an onboard fuel processor would complicate the vehicle system immensely and reduce vehicle fuel economy; storing hydrogen onboard the vehicle would simplify the vehicle system somewhat, but a high-density storage system would have to be developed, as well as an infrastructure, to ensure that hydrogen would be widely available at service stations. All of these trade-offs will have to be analyzed as the program moves forward, and several technology options should be pursued as the basis for a technically, economically, and logistically feasible combination of fuel infrastructure and fuel cell energy converter.
ADEQUACY AND BALANCE OF THE PNGV PROGRAM
Government-sponsored R&D on advanced automotive technologies is primarily being done by the U.S. Department of Energy (DOE). DOE is expected to
provide about $128 million in fiscal year 2000 for PNGV; the program also receives funding from other sources. Consequently, DOE’s funding allocation among technologies, therefore, does not represent the distribution of effort among technologies by PNGV as a whole. Other government agencies (e.g., U.S. Department of Commerce, EPA, the U.S. Department of Transportation, and the National Science Foundation) are expected to provide approximately $110 million of relevant funding, about half of which will be used for emission control projects and half for long-range research.
The committee was informed by PNGV that USCAR had solicited, on a confidential basis, overall figures on expenditures by its members for “PNGV-related” research. These figures show a total investment by the three companies for 1999 of $982 million. Estimates of investments for each of the previous three years was comparable. This very large investment (far higher than the program’s expected 50/50 government/industry matching level) represents major efforts on the part of the industry partners to develop the year 2000 concept cars.
The adequacy of funding for PNGV is difficult to assess because the data provided to the committee are incomplete. Because progress toward meeting Goal 3 appears insufficient to meet the objectives by 2004, one might conclude that resources are inadequate. However, the USCAR partners indicated to the committee that the lack of talented people is a greater handicap than the lack of adequate funding and that they need new ideas (breakthroughs) more than dollars. The committee is inclined to agree because, although increased funding might speed up some projects and also support a broader program more likely to achieve breakthroughs, no important areas of the program seem to be starving for funds. Thus, at the moment, progress in the PNGV program will depend more on inventive solutions and the influx of additional technical people than on increases in resources.
The balance of resources in PNGV is even harder for the committee to assess than funding because no data are available on industry distribution of funding by project. The balance represented in the government programs appears to be appropriately weighted to long-range R&D. The committee assumes that during the development of the concept vehicles, industry resources have been directed primarily toward solving the problems of hybrid vehicle optimization. However, from 2000 to 2004, a different balance will be required, depending on which course individual companies choose to follow. For example, if a company chooses to continue working toward the development of a production prototype vehicle with a CIDI engine in an HEV configuration, then a major effort must be mounted on emissions control of that power plant and a determination made of the benefits of optimizing that system for emissions control rather than for efficiency (i.e., fuel economy and cost penalties involved in meeting the Tier 2 emission standards). If a company chooses to replace the diesel engine with a gasoline spark-ignition engine, which the USCAR partners have indicated can meet the Tier 2 standards, then the optimized fuel economy of that configuration and the diesel
system could be compared. The gasoline system would probably have a somewhat smaller cost penalty than the diesel configuration. The committee believes that PNGV should investigate both of these options, using the best systems analysis and experimental evidence available. The balance of future R&D should then be adjusted according to the results.
ISSUES FOR PNGV BEYOND 2000
The committee encourages PNGV leadership to develop specific objectives for the production-prototype phase of the program with the following goals in mind. First, each automotive company member should develop production-feasible total vehicle concepts that come as close as is practical to the original vehicle performance objectives of Goal 3 (i.e., meeting the mandated emission requirements, balancing the inevitable shortfalls in fuel economy, vehicle performance, and affordability to maximize potential market acceptability). Second, the automotive partners should develop production-feasible versions of new PNGV component technologies that can, in a more evolutionary way, be incorporated into new vehicle designs under Goal 2. The first objective would continue to “stretch” the new technologies and system concepts that, together, have the potential to introduce substantially better fuel economy into the vehicle fleet. The second objective would encourage the development and application of component technologies critical to improving fuel economy by encouraging their early commercial introduction.
Recommendation. PNGV should quantify the trade-off between efficiency and emissions for the power plants under consideration. The PNGV systems-analysis team should attempt to develop and validate vehicle emissions models of sufficient sophistication to provide useful predictions of the emissions potential for a variety of engines (e.g., the compression-ignition direct-injection engine, the gasoline direct-injection engine) and exhaust gas after-treatment systems in various hybrid electric vehicle configurations. The models could be used to help PNGV evaluate the feasibility of meeting the Environmental Protection Agency’s Tier 2 emissions standards with various vehicle system configurations. These data should then be used to establish an appropriate plan for the next phase of the program.
Recommendation. At this stage, PNGV should direct its program toward an appropriate compromise between fuel economy and cost using the best available technology to ensure that a market-acceptable production-prototype vehicle can be achieved by 2004 that meets Tier 2 emission standards.
Recommendation. Given the potential of fuel-cell technology for meeting the efficiency and emissions objectives of the PNGV program, the systems-analysis team should increase its efforts to develop more complete and accurate fuel-cell system and component models to support the development and assessment of fuel-cell technology.
Recommendation. In the area of fuel cell development, PNGV, and especially the U.S. Department of Energy, should emphasize high-risk, high-payoff research in critical areas, such as fuel processing, carbon monoxide-tolerant electrodes, and air-management systems.
Recommendation. PNGV should continue to work on cell chemistry of lithium battery systems to extend life and improve safety, while continuing to lower costs. Performance and cost targets should be refined as overall vehicle systems analysis determines the optimal degree of vehicle hybridization.
Recommendation. As the PNGV program moves toward the 2004 production-prototype milestone, affordability will be a key requirement. Therefore, the development of an efficiently designed and fabricated steel-intensive vehicle being worked on by the American Iron and Steel Institute in the Ultralight Steel Autobody-Advanced Vehicle Concepts (ULSAB-AVC) project should be closely followed, and the possibility of applying the ULSAB concepts to a hybrid steel-aluminum vehicle should be explored.
Recommendation. The committee recognizes the cost reduction potential of DaimlerChrysler’s thermoplastic composite injection-molding technology and urges that this work be continued to bring the technology to successful commercialization.
Recommendation. The committee regards structural crashworthiness, and safety in general, in the design of lightweight PNGV vehicles as extremely important. Using the Oak Ridge National Laboratory car-to-car collision simulation capability, the National Highway Traffic and Safety Administration should support a major study to determine how well lightweight PNGV vehicles would fare in collisions with heavier vehicles and to assess potential improvements.
Recommendation. Defining automotive system/fuels trade-offs and establishing a basis for ensuring that the required fuels are available as higher efficiency vehicles become commercially available will require extensive cooperation among automotive and petroleum industry representatives at all levels of responsibility. Therefore, PNGV should strengthen and expand its cooperative efforts with the petroleum industry, including issues related to fuels for fuel cells. Government leadership will be necessary to initiate this cooperative effort and provide incentives for petroleum company involvement.
Recommendation. PNGV should consider conducting a comprehensive assessment of the consequences of fuel choices for fuel cells and their impact on PNGV’s direction and ultimate goals. PNGV should assess the opportunities and costs for generating hydrogen for fuel cells at existing service stations and storing it on board vehicles and compare the feasibility, efficiency, and safety of this option with onboard fuel reforming. This study would help PNGV determine how much additional effort should be devoted to the development of onboard fuel reforming technologies.