H
Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies

The National Research Council (NRC) has conducted other studies to estimate benefits, costs, and readiness of fuel economy technologies for light-duty vehicles. Indeed, this committee’s task is to update the estimates provided in one of the earlier studies, Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards, which was issued in 2001. The committee discusses several other studies here. The Review of the Research Program of the Partnership for a New Generation of Vehicles: Seventh Report (NRC, 2001) assessed the fuel economy technologies and costs associated with three prototype vehicles built in connection with the Partnership for a New Generation of Vehicles (PNGV) research program to achieve up to three times the fuel economy of a 1994 family sedan. More recent NRC studies that have looked at different aspects of fuel economy technologies include Transitions to Alternative Transportation Technologies—A Focus on Hydrogen (NRC, 2008a), Review of the Research Program of the FreedomCAR and Fuel Partnership: Second Report (NRC, 2008b), and the report from the America’s Energy Future (AEF) Panel on Energy Efficiency, Real Prospects for Energy Efficiency in the United States (NAS-NAE-NRC, 2010). Even though the recent report Transitions to Alternative Transportation Technologies—Plug-In Hybrid Electric Vehicles (NRC, 2009) was not strictly a report on fuel economy technology, it did address the costs and benefits of plug-in electric vehicles.

While the tasks required under each study are different, some of their analyses of costs, efficiencies, and prospects for the various technologies overlap and are reviewed here. However, the committee does not attempt to review the findings of any studies other than those of the NRC. It simply comments on them, as appropriate, to the degree that the NRC reports are based on them.

REVIEW OF THE RESEARCH PROGRAM OF THE PARTNERSHIP FOR A NEW GENERATION OF VEHICLES, SEVENTH REPORT

The task of the NRC Standing Committee to Review the Research Program of the PNGV (NRC PNGV committee) was to examine the research program, communicate the program’s progress to government and industry participants, and identify barriers to the program’s success. The PNGV program was a cooperative research and development program between the government and the United States Council for Automotive Research, whose members include the three original equipment manufacturers (OEMs) in the United States: DaimlerChrysler Corporation, Ford Motor Company, and General Motors Corporation. The PNGV was envisioned to allow the parties to cooperate on precompetitive research activities that would ultimately result in the deployment of technologies to reduce our country’s fuel consumption and emissions of carbon dioxide. The PNGV aimed to improve the competitiveness of the U.S. manufacturing base for future generations of vehicles and to introduce innovative technologies into conventional vehicles in order to improve fuel consumption or reduce emissions. The final goal of the PNGV program was to develop prototype vehicles that achieve up to three times the average fuel economy of a 1994 family sedan. It was recognized that these new vehicles would have to be sold in high volume in order to have an impact. For this reason, the strategy for the prototype vehicle was to develop an affordable family sedan with a fuel economy of up to 80 mpg that maintained the performance, size, and safety standards of the vehicles of that time. After 2002, the program transitioned to the FreedomCAR and Fuel Research (FreedomCAR) Program, discussed in the following section.

Each of the three automobile companies involved in the PNGV program built its own prototype concept vehicles since this could not be done in the context of precompetitive research. By the time of the seventh NRC report, all three companies had built prototypes that met the then-extant performance, comfort, cargo space, utility, and safety requirements. These prototype vehicles could not, however, meet the price target while simultaneously improving fuel economy to near 80 mpg. The DaimlerChrysler prototype foresaw a price premium of $7,500, while the other two did not announce any price premium associated with their vehicles. All three concept vehicles used hybrid electric



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H Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies The National Research Council (NRC) has conducted was to examine the research program, communicate the other studies to estimate benefits, costs, and readiness of fuel program’s progress to government and industry participants, economy technologies for light-duty vehicles. Indeed, this and identify barriers to the program’s success. The PNGV committee’s task is to update the estimates provided in one of program was a cooperative research and development pro- the earlier studies, Effectiveness and Impact of Corporate Aver- gram between the government and the United States Council age Fuel Economy (CAFE) Standards, which was issued in for Automotive Research, whose members include the three 2001. The committee discusses several other studies here. The original equipment manufacturers (OEMs) in the United States: DaimlerChrysler Corporation, Ford Motor Company, Review of the Research Program of the Partnership for a New Generation of Vehicles: Seventh eport (NRC, 2001) assessed and General Motors Corporation. The PNGV was envisioned R the fuel economy technologies and costs associated with three to allow the parties to cooperate on precompetitive research prototype vehicles built in connection with the Partnership for activities that would ultimately result in the deployment of a New Generation of Vehicles (PNGV) research program to technologies to reduce our country’s fuel consumption and achieve up to three times the fuel economy of a 1994 family emissions of carbon dioxide. The PNGV aimed to improve sedan. More recent NRC studies that have looked at different the competitiveness of the U.S. manufacturing base for future aspects of fuel economy technologies include Transitions to generations of vehicles and to introduce innovative technolo- gies into conventional vehicles in order to improve fuel con- Alternative Transportation Technologies—A Focus on Hydro- gen (NRC, 2008a), Review of the Research Program of the sumption or reduce emissions. The final goal of the PNGV FreedomCAR and Fuel Partnership: Second Report (NRC, program was to develop prototype vehicles that achieve up 2008b), and the report from the America’s Energy Future to three times the average fuel economy of a 1994 family (AEF) Panel on Energy Efficiency, Real Prospects for Energy sedan. It was recognized that these new vehicles would Efficiency in the United States (NAS-NAE-NRC, 2010). Even have to be sold in high volume in order to have an impact. though the recent report Transitions to Alternative Transporta- For this reason, the strategy for the prototype vehicle was tion Technologies—Plug-In Hybrid Electric Vehicles (NRC, to develop an affordable family sedan with a fuel economy 2009) was not strictly a report on fuel economy technology, it of up to 80 mpg that maintained the performance, size, and did address the costs and benefits of plug-in electric vehicles. safety standards of the vehicles of that time. After 2002, the While the tasks required under each study are different, program transitioned to the FreedomCAR and Fuel Research some of their analyses of costs, efficiencies, and prospects (FreedomCAR) Program, discussed in the following section. for the various technologies overlap and are reviewed here. Each of the three automobile companies involved in the However, the committee does not attempt to review the find- PNGV program built its own prototype concept vehicles ings of any studies other than those of the NRC. It simply since this could not be done in the context of precompetitive comments on them, as appropriate, to the degree that the research. By the time of the seventh NRC report, all three NRC reports are based on them. companies had built prototypes that met the then-extant performance, comfort, cargo space, utility, and safety re- quirements. These prototype vehicles could not, however, REVIEW OF THE RESEARCH PROGRAM OF THE meet the price target while simultaneously improving fuel PARTNERSHIP FOR A NEW GENERATION OF economy to near 80 mpg. The DaimlerChrysler prototype VEHICLES, SEVENTH REPORT foresaw a price premium of $7,500, while the other two The task of the NRC Standing Committee to Review the did not announce any price premium associated with their Research Program of the PNGV (NRC PNGV committee) vehicles. All three concept vehicles used hybrid electric 181

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182 ASSESSMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES power trains with small, turbocharged, compression-ignition plug-in hybrid electric vehicles (PHEVs). The NRC has thus direct-injection engines using diesel fuel. All three were far reviewed the FreedomCAR and Fuel Partnership twice, start-stop hybrids that shut the engine off when idling. The with reports published in 2005 and 2008. In the second of report from the NRC PNGV committee estimated that dual- these reports, one of the NRC FreedomCAR committee’s mode batteries would probably cost $1,000 to $1,500 per tasks was to comment on the balance and adequacy of the battery unit (1.5 kWh), or $670 to $1,000 per kWh (NRC, efforts and on the progress achieved since the 2005 report. 2001). Each company took a different route to reduce the The conclusions and recommendations of the second report vehicle mass and aerodynamic drag and to supply power focus on the Partnership’s management and oversight but for auxiliary loads. The high cost of the lightweight mate - also provide the FreedomCAR committee’s opinion on the rials and electronic control systems made the price target readiness of new fuel economy technologies. unattainable. In addition, the cost of the compression- The NRC FreedomCAR committee report recognizes ignition direct-injection engine was greatly increased by the that more efficient IC engines will contribute the most to exhaust-gas after-treatment systems to control emissions. reducing fuel consumption and emissions in the near term. In the middle of the PNGV program, the Tier 2 emission The Partnership focuses research on lean-burn, direct- standard was promulgated, and the NRC PNGV committee injection engines for both diesel- and gasoline-fueled ve - believed that the ability of the diesel engine to meet emis- hicles, specifically on low-temperature combustion engines sions targets was not clear. and aftertreatment of the exhaust. The report recognizes The NRC PNGV committee reported that the PNGV that, after completing the research necessary to prove a program had made significant progress in implementing technology’s viability, there are typically several years desirable technologies as fast as possible. Each of the three of prototyping and developing manufacturing processes automobile manufacturers in the PNGV demonstrated a before the technology can be introduced into the vehicle hybrid electric vehicle before the end of the Partnership in fleet. Because of the urgent need to reduce vehicle fuel 2004. They had developed the concept vehicles by 2000, but consumption, the development phase of these technologies the goal of the development of a preproduction prototype by has been accelerated while researchers are still studying 2004 was not met because of the termination of the PNGV the controlling thermochemistry of low-temperature com - program. Indeed, the manufacturing and engineering innova- bustion. The result is close coordination between those tions that came out of the PNGV program were implemented looking to expand the fundamental knowledge base and before 2000. In the end, the three OEMs demonstrated that those investigating applications. The report from the NRC a production medium-size passenger car could be produced FreedomCAR committee recommends that the Partnership that achieved 80 mpg, and one OEM (DaimlerChrysler) investigate the impact on emissions of combustion mode demonstrated that such a vehicle could be produced at a cost switching and transient operation with low-temperature penalty of less than $8,000. combustion, and it questions how much exhaust energy can actually be recovered. Furthermore, the NRC FreedomCAR committee suggests the Partnership closely analyze the THE FREEDOMCAR AND FUEL RESEARCH PROGRAM cost-effectiveness of the exhaust gas heat recovery research REPORT and the potential fuel efficiency benefits before deciding The task of the NRC Committee on Review of the whether to pursue this research further. FreedomCAR and Fuel Research Program (NRC Freedom- Another goal of the FreedomCAR and Fuel Partnership CAR committee) is to assess the FreedomCAR and Fuel is to develop, by 2015, battery storage for hybrid elec - Partnership’s management and the research and develop- tric vehicles that has a 15-year life and a pulse power of ment activities overseen by the Partnership. The Partner- 25 kilowatts (kW), with 1 kW of pulse power costing $20. ship, started in 2002, built on the earlier PNGV program. This effort focuses on lithium (Li) ion batteries, which are FreedomCAR, like PNGV, is a collaboration between the simultaneously in both the research phase, as the knowledge government and industry to support a wide range of pre- base for specific electrochemical systems is expanded, competitive research in automotive transportation. The and the development phase, as the batteries are built and Partnership’s goal is to study technologies that will help tested. Significant progress had been made since the first the United States transition to an automotive fleet free from FreedomCAR report (NRC, 2005, 2008b). The Partnership petroleum use and harmful emissions (NRC, 2005). The has demonstrated batteries that exceed the requirement for vision of the Partnership is to enable a transition pathway a 300,000-cycle lifetime, that have longer calendar lives, that starts with improving the efficiency of today’s internal and that operate over a wider temperature range than earlier combustion (IC) engines, increasing the use of hybrid elec- batteries. The NRC FreedomCAR committee recognized tric vehicles, and supporting research in fuel-cell-powered that cost is the primary barrier for introduction of the vehicles so that a decision can be reached in 2015 on the Li-ion battery to the market and commends the Partner- economic and technological viability of hydrogen-powered ship for researching lower cost materials for the cathode vehicles. In 2009, a greater emphasis began to be placed on and the microporous separator. The report from the NRC

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183 APPENDIX H FreedomCAR committee recommended that the Partnership in a position to begin significant commercialization until at do a thorough cost analysis of the Li-ion batteries under least 2020, 5 years later than the target date assumed in the development to account for recent process and materials hydrogen study. costs and for increased production rate costs. The task also called for the NRC hydrogen committee to A 50 percent reduction in total vehicle weight at no addi- consider whether other technologies could achieve signifi- tional cost is another key goal of the Partnership; it would cant CO2 and oil reductions by 2020. The NRC hydrogen rely on the widespread application of advanced high-strength committee considered improvements to spark-ignition (SI) steels, aluminum alloys, cast magnesium, and carbon-fiber- engines, compression-ignition (CI) engines, vehicle trans- reinforced plastics. The NRC FreedomCAR committee missions, and hybrid vehicle technologies as well as reduc- concluded that the goal of price parity for the lightweight tions in weight and other vehicle load reductions. Improve- materials is insurmountable within the time frame of the ments also could come in the form of reductions in weight Partnership (NRC, 2008b). However, the 50 percent weight and similar improvements. The technical improvements that reduction goal is critical for the Partnership’s overall vision can be applied to SI engines include variable valve timing of a hydrogen-fueled car. The NRC FreedomCAR commit- and lift, camless valve actuation, cylinder deactivation, the tee went beyond that, saying the weight reduction would be use of gasoline direct injection with turbocharging, and in- mandatory even with the associated cost penalty, because the telligent start-stop, which involves engine shutoff when the alternative adjustments to the engine and batteries would cost vehicle idles. Improvements in vehicle transmissions include more. The NRC report recommends maintaining the 50 per- the use of conventional 6/7/8-speed automatic transmissions cent weight reduction goal and analyzing cost-effectiveness and automated manual transmissions. This report repeats an to confirm that the added cost of weight reduction can be estimate from Duleep (2007) that combining the projections offset by modifying the fuel cell and battery goals. for improvements in the engine, transmission, weight, para- sitic loss (including friction losses, rolling resistance, and air drag), accessories, and idle-stop components could reduce THE HYDROGEN REPORT fuel consumption in 2015 by 21 to 29 percent relative to The tasks of the Committee on Assessment of Resource today’s vehicles and in 2025 by 31 to 37 percent. Table H.1 Needs for Fuel Cell and Hydrogen Technologies (the NRC shows the improvements estimated for SI engines attribut- hydrogen committee) was to establish the maximum practi- able to these approaches. The NRC hydrogen report also cable number of vehicles that could be fueled by hydrogen quotes studies by Heywood and colleagues at Massachusetts by 2020 and to discuss the public and private funding needed Institute of Technology (MIT) on the fuel efficiency of light- to reach that number. The NRC hydrogen committee as- duty vehicles (Weiss et al., 2000; Heywood, 2007; Kasseris sumed that (1) the technical goals for fuel cell vehicles, and Heywood, 2007; Kromer and Heywood, 2007). The fuel which were less aggressive than those of the FreedomCAR economy improvements noted in the MIT work result from Partnership, are met; (2) that consumers would readily accept changes to the engines and transmissions and appropriate such vehicles; (3) that government policies would drive the reductions in vehicle weight. The MIT work assumes that the introduction of fuel cell vehicles and hydrogen production improvements are aimed entirely at reducing fuel consump- and infrastructure at least to the point where fuel cell vehicles tion. Table H.2 shows the improvements in fuel economy are competitive on the basis of lifecycle cost; and (4) that oil compared to a 2005 SI engine vehicle that MIT estimates prices are at least $100 per barrel by 2020 (NRC, 2008a). could be achieved by 2030, although the NRC hydrogen Thus, the scenarios developed in the hydrogen report are not committee assumed that these levels of fuel economy would projections but a maximum possible future market if all as- not be available as quickly. sumptions are met. The NRC hydrogen committee concluded that although durable fuel cell systems at significantly lower costs are likely to be increasingly available for light-duty vehicles over the next 5 to 10 years, the FreedomCAR Part- TABLE H.1 Potential Reductions in Fuel Consumption nership goals for 2015 are not likely to be met. The NRC (gallons per mile) for Spark-Ignition Vehicles Expected hydrogen committee also concluded that commercialization from Advances in Conventional Vehicle Technology by and growth of these hydrogen fuel cell vehicles could get Category, Projected to 2025 under way by 2015 if supported by strong government poli- 2006-2015 2016-2025 cies. Those conclusions are more optimistic than the conclu- (%) (%) sions on fuel cells contained in this report, whose committee Engine and transmission 12-16 18-22 (though it did not consider the potential impact of policies Weight, drag, and tire loss reduction 6-9 10-13 on fuel cell market potential) does not expect progress on Accessories 2-3 3-4 fuel cell costs and technology to be as rapid as expected by Intelligent start-stop 3-4 3-4 the NRC hydrogen committee. Further, one OEM that is ag- NOTE: Values for 2016-2025 include those of 2006-2015. gressively pursuing fuel cell vehicles will probably not be SOURCE: Duleep (2007).

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184 ASSESSMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES TABLE H.2 Comparison of Projected Improvements in Vehicle Fuel Consumption from Advances in Conventional Vehicle Technology Fuel Consumption Relative to 2005 Relative to 2030 Relative to 2005 Relative to 2030 Gasolinea Gasolinea Gasolineb Gasolineb (L/100 km) 2005 Gasoline 8.8 1.00 2005 Diesel 7.4 0.84 2005 Turbo 7.9 0.9 2005 Hybrid 5.7 0.65 2030 Gasoline 5.5 0.63 1.00 2030 Diesel 4.7 0.53 0.85 0.61 1.00 2030 Turbo 4.9 0.56 0.89 0.45 0.77 2030 Hybrid 3.1 0.35 0.56 0.54 0.88 2030 Plug-in 1.9 0.21 0.34 0.38 0.615 aFrom Kromer and Heywood (2007). bFrom Weiss et al. (2000). Although the NRC hydrogen committee acknowledges to include plug-in hybrid electric vehicles. The committee the potential for hybrids outlined in Kromer and Heywood, reconvened to examine the issues associated with PHEVs it concluded that advances in hybrid technology are more and wrote Transitions to Alternative Transportation Tech- likely to lower the cost of battery packs than to increase fuel nologies—Plug-in Hybrid Electric Vehicles (referred to here economy significantly. This would increase their appeal to as the PHEV report) to that additional task (NRC, 2009). consumers relative to conventional vehicles and, thus, their In accordance with the committee’s statement of task, the market share (Kromer and Heywood, 2007). To simplify the PHEV report does the following: analysis in the hydrogen report, the NRC hydrogen commit- tee assumed that hybrids reduce fuel consumption a constant • Reviews the current and projected status of PHEV 29 percent annually relative to conventional vehicles, which technologies. also improve each year. This value is within the range of the • Considers the factors that will affect how rapidly potential for power split hybrids in the present report. PHEVs would enter the marketplace, including the Thus, the NRC hydrogen committee judged that hybrid interface with the electric transmission and distribution electric vehicles could, if focused on vehicle efficiency, system. consistently reduce fuel consumption 29 percent relative • Determines a maximum practical penetration rate for to comparable evolutionary internal combustion engine PHEVs consistent with the time frame of the 2008 vehicles (ICEVs). Although this judgment is conservative Hydrogen Report and other factors considered in that compared to that of Kromer and Heywood, it still leads to report. a 60-mpg average for new spark-ignition hybrids by 2050. • Incorporates PHEVs into the models used in the 2008 This means that hybrid technologies will have reached their Hydrogen Report to estimate the costs and impacts greatest fuel consumption reductions by 2009 and that future on petroleum consumption and carbon dioxide (CO2) improvements in hybrid vehicle fuel economy would be pri- emissions. marily attributable to the same technologies that reduce fuel consumption in conventional vehicles. Thus, hybrid vehicles As in this report, the PHEV report considered two types reduce fuel consumption by 2.6 percent per year from 2010 of PHEVs, a PHEV10 with an all-electric range of 10 miles through 2025, 1.7 percent per year in 2025-2035, and 0.5 and a PHEV40 with an all-electric range of 40 miles. Both percent per year between 2035 and 2050, the same as do reports use the same architectures as this committee, which evolutionary ICEVs. include a spark-ignited internal combustion engine, two electrical machines, power electronics, and a Li-ion bat - tery. Only the first task relates to our report, and comparing PLUG-IN HYBRID ELECTRIC REPORT the two, it is necessary to separate the current technology After the publication of the NRC report Transitions status and the projections. The assessment of current tech - nologies in the PHEV report is in close agreement with the to Alternative Transportation Technologies—A Focus on ydrogen (NRC, 2008), the U.S. Department of Energy assessment of this committee. Both discuss the different H asked the Committee on Assessment of Resource Needs for battery chemistries and the advantages and problems of Fuel Cell and Hydrogen Technologies to expand its analysis each and point out how PHEVs differ from batteries for

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185 APPENDIX H HEVs, because the critical parameter is the energy available 2010), the panel estimated the current contributions and fu- as opposed to the power needs. The discussion of power ture potential of existing technologies. In addition, the energy electronics and motors and generators within the PHEV efficiency panel estimated the potential for new technologies report again generally parallels what is in this report. There that could begin to be commercially deployed in the next are some differences in terms of the technological needs. decade, the associated impacts of these technologies, and For example, the PHEV report assumes that liquid cooling the projected costs per unit of reduction in energy demand. is assumed to be required for the PHEV40 battery packs The panel’s work on light-duty vehicles is summarized in whereas this report assumes air cooling will be sufficient. the following sections. The PHEV report was required to project and analyze the technology costs to 2050, while this report stopped at Gasoline SI Engine 2025. The methodology used is similar, and in both cases the costs were built up by adding the costs of the new com- Gasoline SI engine efficiency improvements contem - ponents needed compared to an internal combustion engine plated by the NRC energy efficiency panel included engine vehicle. Costs were deducted for components such as engine friction reduction, smart cooling systems, variable valve simplification and the elimination of the transmission. The timing (VVT), two- and three-step variable valve lift (VVL), information was obtained from OEMs and suppliers in a cylinder deactivation, direct injection (DI), and turbocharg- similar way. For the PHEV10 the cost estimates in this report ing with engine downsizing. Most of these are already in are within 5 percent of those in the PHEV report and within 3 low-volume production, and all could be deployed in large percent for the 2020 to 2030 time frame. For the PHEV 40 the volumes in the next decade. In 15 to 20 years, technologies committee’s costs are significantly lower: by 45 percent for such as camless valve actuation, continuous variable valve current costs and 42 percent for the 2020 to 2030 time frame. lift (CVVL), and homogeneous-charge compression ignition In view of the uncertainties of actual costs and how these (HCCI) could be deployed. The conclusions hoped for in would translate as retail price equivalents, the difference can connection with the deployment of camless valve actuation be attributed to a difference in professional judgment. and HCCI are more optimistic than those anticipated for fuel A more difficult question is the rate at which the cost of cells in this report. The NRC energy efficiency panel survey the battery will come down, and what makes projections even shows the above technologies have the potential to reduce harder is the injection of a substantial amount of capital by vehicle fuel consumption by 10 to 15 percent by 2020 and by the administration and the enthusiasm of investors. Basically an additional 15 to 20 percent by 2030 (EEA, 2007; Kasseris there are two ways of looking at future cost declines: and Heywood, 2007; Ricardo, Inc., 2008; and NRC, 2008a). • People making these very large investments in both ve- Diesel CI Engine hicles and lithium ion batteries must expect the market to take off. Since the success of vehicle electrification Owing to high compression ratios and reduced pumping depends on reductions in the price of battery by factors losses, turbocharged diesel engines offer a 20 to 25 percent of two or three, investors and the administration must efficiency advantage over gasoline SI engines when adjusted be optimistic that large cost reductions will occur. for the higher energy density of diesel fuel. The primary ef- • A more pessimistic perspective is that lithium ion is a ficiency improvements in CI engines are likely to come from well-developed technology with billions of individual increased power density, improved engine system manage- cells being produced. ment, more sophisticated fuel injection systems, and im- proved combustion processes. New exhaust after-treatment How much improvement can one realistically expect in technologies are emerging that reduce emissions of particu- the 10-year horizon of the report? Both reports take a fairly late matter and oxides of nitrogen to levels comparable to conservative viewpoint in terms of the cost reductions of bat- those of SI engines. One challenge for diesel engines noted teries over time and, taking into account developments in the by the NRC energy efficiency panel is the added costs and last year, both reports may turn out to be overly conservative. fuel economy penalties associated with the aftertreatment systems for reducing these emissions (Bandivadekar et al., 2008; Johnson, 2008; Ricardo, Inc., 2008). AEF ENERGY EFFICIENCY PANEL REPORT The America’s Energy Future Energy Efficiency Panel Gasoline Hybrid Electric Vehicle examined the technical potential for reducing energy demand by improving efficiency in transportation, lighting, heating, The primary efficiency benefits of a gasoline hybrid cooling, and industrial processes using existing technolo- electric vehicle (HEV) noted by the NRC energy efficiency gies, technologies developed but not yet widely utilized, panel are realized by eliminating idling, including regen- and prospective technologies. In its report, Real Prospects erative braking, downsizing the engine, and operating at for Energy Efficiency in the United States (NAS-NAE-NRC, more efficient engine conditions than current SI engines.

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186 ASSESSMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES The NRC energy efficiency panel classifies hybrids on how TABLE H.3 Expected Transmission System Efficiency well their electric motor and generator function. Belt-driven Improvements starter-generator systems eliminate engine idle to reduce fuel Transmission Efficiency (%) consumption by 4 to 6 percent. Integrated starter-generator Current automatic transmission (4- and 5-speed) 84-89 systems that recover energy from regenerative braking, along Automatic transmission (6- or 7-speed) 93-95 with the start-stop function, can achieve a fuel consumption Dual-clutch transmission (wet clutch) 86-94 reduction of 10 to 12 percent. A parallel full hybrid with Dual-clutch transmission (dry clutch) 90-95 power assist, such as Honda’s integrated motor assist system, Continuously variable transmission 87-90 can reduce fuel consumption by more than 20 to 25 percent, SOURCE: NAS-NAE-NRC (2010), quoting Ricardo, Inc. (2008) and EEA whereas more complex systems using two motors such as (2007). Toyota’s hybrid synergy drive can reduce fuel consumption more than 30 percent. Some diesel HEV prototypes are now being developed. Diesel HEVs could be 10 percent more ef- ficient than an equivalent gasoline hybrid, which translates to engine to operate near its maximum efficiency, the current a 20 percent lower diesel fuel consumption when greater fuel estimates of CVT efficiency are lower than the corresponding density is factored in. A diesel HEV would be significantly efficiencies of 6- or 7-speed automatic transmissions. CVTs more expensive than a gasoline HEV. have been in low-volume production for well over a decade. Vehicle Technologies and Transmission Improvements Summary and Costs of Potential Light-Duty Vehicle Efficiency Improvements The NRC energy efficiency panel notes that reducing the vehicle weight by 10 percent is commonly thought to Table H.4 shows plausible levels of petroleum reduc- reduce fuel consumption by 5 to 7 percent when accompa- tion potential through vehicle technology improvements nied by appropriate engine downsizing to maintain constant estimated by the NRC energy efficiency panel. The NRC performance. Preliminary vehicle simulation results suggest energy efficiency panel developed its estimates from a that the relative benefits of weight reduction may be smaller number of sources (An and Santini, 2004; Wohlecker et al., for some types of hybrid vehicles (An and Santini, 2004; 2007; Cheah et al., 2007; NPC, 2007; and NRC, 2004). The Wohlecker et al., 2007). In a conventional vehicle the en- estimates shown in Table H.4 assume that vehicle size and ergy used to accelerate the mass is mostly dissipated in the performance, such as the power-to-weight ratio and accel- brakes, while in a hybrid a significant fraction of this brak- eration, are kept constant at today’s levels. The evolutionary ing energy is recovered, sent back to the battery, and reused. improvements briefly outlined above and discussed in more Thus weight reduction in hybrid vehicles has a much smaller detail in the NRC energy efficiency panel report can reduce effect on reducing fuel consumption than such reduction in the fuel consumption of a gasoline ICE vehicle by up to 35 non-hybrid vehicles. Additional weight reduction can be percent in the next 25 years. The diesel engine currently achieved by vehicle redesign and downsizing as well as by offers a 20 percent reduction in fuel consumption over a substituting lighter-weight materials in vehicle construction, gasoline engine and, while the diesel engine will continue For example, downsizing a passenger car by one EPA size- to evolve, the gap between gasoline and diesel vehicle fuel class can reduce vehicle weight by approximately 10 percent consumption is likely to narrow to a 15 percent improvement. (Cheah et al., 2007). Additional sources of fuel consump- Hybrid vehicles (including PHEVs) have a greater potential tion benefits noted by the NRC energy efficiency panel are for improvement and can deliver deeper reductions in vehicle from improvements in tires. A recent NRC report on tires fuel consumption, although they continue to depend on and passenger vehicle fuel economy (NRC, 2006) agrees petroleum (or alternative liquid fuels, such as biofuels). Bat- with estimates in the literature (Schuring and Futamura, tery electric vehicles (BEVs) and fuel cell vehicles (FCVs) 1990) that the vehicle fuel consumption will be reduced are two longer-term technologies. by 1 or 2 percent for a reduction of 0.001 in the coefficient The cost estimates developed by the NRC energy effi- of rolling resistance of passenger tires—equivalent to a 10 ciency panel shown in Table H.4 represent the approximate percent reduction in overall rolling resistance. The NRC en- incremental retail price of future vehicle systems, including ergy efficiency panel also discussed transmission efficiency emissions control costs, compared to a 2005 baseline gaso - improvements likely in the next 10 to 20 years through an line ICE vehicle (NHTSA, 2007; EEA, 2007; Bandivadekar increase in the number of gears and through improvements in et al., 2008). The first column shown is for a midsize car; the bearings, gears, sealing elements, and the hydraulic system. second column is for a typical pickup truck or SUV. These Table H.3 lists the efficiency improvements considered by retail prices are based on the costs associated with produc - the NRC energy efficiency panel that can be expected from ing a vehicle at the manufacturing plant gate. To account different transmission systems in this time frame. Note that for distribution costs and manufacturer and dealer profit while a continuously variable transmission (CVT) allows the margins, production costs were multiplied by a factor of

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187 APPENDIX H TABLE H.4 Plausible Reductions in Petroleum Use from Vehicle Efficiency Improvements over the Next 25 Years and Estimated Incremental Cost of Advanced Vehicles Relative to a Baseline 2005 Standard Gasoline Vehicle Petroleum Consumption Incremental Retail Price (gasoline equivalent) (2007 dollars) Relative to Current Gasoline Relative to 2035 Gasoline Propulsion System ICE ICE Car Light Truck Current gasoline 1 — 0 0 Current diesel 0.8 — 1,700 2,100 Current HEV 0.75 — 4,900 6,300 2035 gasoline 0.65 1 2,000 2,400 2035 diesel 0.55 0.85 3,600 4,500 2035 HEV 0.4 0.6 4,500 5,500 2035 PHEV 0.2 0.3 7,800 10,500 2035 BEV None — 16,000 24,000 2035 hydrogen FCV None — 7,300 10,000 NOTE: BEV, battery electric vehicle; FCV, fuel cell vehicle; HEV, hybrid electric vehicle; ICE, internal combustion engine. SOURCE: Report from the NRC Panel on Energy Efficiency (NAS-NAE-NRC, 2010) quoting Bandivadekar et al. (2008). 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