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Assessment of Fuel Economy Technologies for Light-Duty Vehicles (2011)

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

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Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×

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

Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×

power trains with small, turbocharged, compression-ignition direct-injection engines using diesel fuel. All three were start-stop hybrids that shut the engine off when idling. The report from the NRC PNGV committee estimated that dualmode batteries would probably cost $1,000 to $1,500 per battery unit (1.5 kWh), or $670 to $1,000 per kWh (NRC, 2001). Each company took a different route to reduce the vehicle mass and aerodynamic drag and to supply power for auxiliary loads. The high cost of the lightweight materials and electronic control systems made the price target unattainable. In addition, the cost of the compression-ignition direct-injection engine was greatly increased by the exhaust-gas after-treatment systems to control emissions. In the middle of the PNGV program, the Tier 2 emission standard was promulgated, and the NRC PNGV committee believed that the ability of the diesel engine to meet emissions targets was not clear.

The NRC PNGV committee reported that the PNGV program had made significant progress in implementing desirable technologies as fast as possible. Each of the three automobile manufacturers in the PNGV demonstrated a hybrid electric vehicle before the end of the Partnership in 2004. They had developed the concept vehicles by 2000, but the goal of the development of a preproduction prototype by 2004 was not met because of the termination of the PNGV program. Indeed, the manufacturing and engineering innovations that came out of the PNGV program were implemented before 2000. In the end, the three OEMs demonstrated that a production medium-size passenger car could be produced that achieved 80 mpg, and one OEM (DaimlerChrysler) demonstrated that such a vehicle could be produced at a cost penalty of less than $8,000.

THE FREEDOMCAR AND FUEL RESEARCH PROGRAM REPORT

The task of the NRC Committee on Review of the FreedomCAR and Fuel Research Program (NRC Freedom-CAR committee) is to assess the FreedomCAR and Fuel Partnership’s management and the research and development activities overseen by the Partnership. The Partnership, started in 2002, built on the earlier PNGV program. FreedomCAR, like PNGV, is a collaboration between the government and industry to support a wide range of precompetitive research in automotive transportation. The Partnership’s goal is to study technologies that will help the United States transition to an automotive fleet free from petroleum use and harmful emissions (NRC, 2005). The vision of the Partnership is to enable a transition pathway that starts with improving the efficiency of today’s internal combustion (IC) engines, increasing the use of hybrid electric vehicles, and supporting research in fuel-cell-powered vehicles so that a decision can be reached in 2015 on the economic and technological viability of hydrogen-powered vehicles. In 2009, a greater emphasis began to be placed on plug-in hybrid electric vehicles (PHEVs). The NRC has thus far reviewed the FreedomCAR and Fuel Partnership twice, with reports published in 2005 and 2008. In the second of these reports, one of the NRC FreedomCAR committee’s tasks was to comment on the balance and adequacy of the efforts and on the progress achieved since the 2005 report. The conclusions and recommendations of the second report focus on the Partnership’s management and oversight but also provide the FreedomCAR committee’s opinion on the readiness of new fuel economy technologies.

The NRC FreedomCAR committee report recognizes that more efficient IC engines will contribute the most to reducing fuel consumption and emissions in the near term. The Partnership focuses research on lean-burn, direct-injection engines for both diesel- and gasoline-fueled vehicles, specifically on low-temperature combustion engines and aftertreatment of the exhaust. The report recognizes that, after completing the research necessary to prove a technology’s viability, there are typically several years of prototyping and developing manufacturing processes before the technology can be introduced into the vehicle fleet. Because of the urgent need to reduce vehicle fuel consumption, the development phase of these technologies has been accelerated while researchers are still studying the controlling thermochemistry of low-temperature combustion. The result is close coordination between those looking to expand the fundamental knowledge base and those investigating applications. The report from the NRC FreedomCAR committee recommends that the Partnership investigate the impact on emissions of combustion mode switching and transient operation with low-temperature combustion, and it questions how much exhaust energy can actually be recovered. Furthermore, the NRC FreedomCAR committee suggests the Partnership closely analyze the cost-effectiveness of the exhaust gas heat recovery research and the potential fuel efficiency benefits before deciding whether to pursue this research further.

Another goal of the FreedomCAR and Fuel Partnership is to develop, by 2015, battery storage for hybrid electric vehicles that has a 15-year life and a pulse power of 25 kilowatts (kW), with 1 kW of pulse power costing $20. This effort focuses on lithium (Li) ion batteries, which are simultaneously in both the research phase, as the knowledge base for specific electrochemical systems is expanded, and the development phase, as the batteries are built and tested. Significant progress had been made since the first FreedomCAR report (NRC, 2005, 2008b). The Partnership has demonstrated batteries that exceed the requirement for a 300,000-cycle lifetime, that have longer calendar lives, and that operate over a wider temperature range than earlier batteries. The NRC FreedomCAR committee recognized that cost is the primary barrier for introduction of the Li-ion battery to the market and commends the Partnership for researching lower cost materials for the cathode and the microporous separator. The report from the NRC

Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×

FreedomCAR committee recommended that the Partnership do a thorough cost analysis of the Li-ion batteries under development to account for recent process and materials costs and for increased production rate costs.

A 50 percent reduction in total vehicle weight at no additional cost is another key goal of the Partnership; it would rely on the widespread application of advanced high-strength steels, aluminum alloys, cast magnesium, and carbon-fiber-reinforced plastics. The NRC FreedomCAR committee concluded that the goal of price parity for the lightweight materials is insurmountable within the time frame of the Partnership (NRC, 2008b). However, the 50 percent weight reduction goal is critical for the Partnership’s overall vision of a hydrogen-fueled car. The NRC FreedomCAR committee went beyond that, saying the weight reduction would be mandatory even with the associated cost penalty, because the alternative adjustments to the engine and batteries would cost more. The NRC report recommends maintaining the 50 percent weight reduction goal and analyzing cost-effectiveness to confirm that the added cost of weight reduction can be offset by modifying the fuel cell and battery goals.

THE HYDROGEN REPORT

The tasks of the Committee on Assessment of Resource Needs for Fuel Cell and Hydrogen Technologies (the NRC hydrogen committee) was to establish the maximum practicable number of vehicles that could be fueled by hydrogen by 2020 and to discuss the public and private funding needed to reach that number. The NRC hydrogen committee assumed that (1) the technical goals for fuel cell vehicles, which were less aggressive than those of the FreedomCAR Partnership, are met; (2) that consumers would readily accept such vehicles; (3) that government policies would drive the introduction of fuel cell vehicles and hydrogen production and infrastructure at least to the point where fuel cell vehicles are competitive on the basis of lifecycle cost; and (4) that oil prices are at least $100 per barrel by 2020 (NRC, 2008a). Thus, the scenarios developed in the hydrogen report are not projections but a maximum possible future market if all assumptions 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 Partnership goals for 2015 are not likely to be met. The NRC hydrogen committee also concluded that commercialization and growth of these hydrogen fuel cell vehicles could get under way by 2015 if supported by strong government policies. Those conclusions are more optimistic than the conclusions on fuel cells contained in this report, whose committee (though it did not consider the potential impact of policies on fuel cell market potential) does not expect progress on fuel cell costs and technology to be as rapid as expected by the NRC hydrogen committee. Further, one OEM that is aggressively pursuing fuel cell vehicles will probably not be in a position to begin significant commercialization until at least 2020, 5 years later than the target date assumed in the hydrogen study.

The task also called for the NRC hydrogen committee to consider whether other technologies could achieve significant CO2 and oil reductions by 2020. The NRC hydrogen committee considered improvements to spark-ignition (SI) engines, compression-ignition (CI) engines, vehicle transmissions, and hybrid vehicle technologies as well as reductions in weight and other vehicle load reductions. Improvements also could come in the form of reductions in weight and similar improvements. The technical improvements that can be applied to SI engines include variable valve timing and lift, camless valve actuation, cylinder deactivation, the use of gasoline direct injection with turbocharging, and intelligent start-stop, which involves engine shutoff when the vehicle idles. Improvements in vehicle transmissions include the use of conventional 6/7/8-speed automatic transmissions and automated manual transmissions. This report repeats an estimate from Duleep (2007) that combining the projections for improvements in the engine, transmission, weight, parasitic loss (including friction losses, rolling resistance, and air drag), accessories, and idle-stop components could reduce fuel consumption in 2015 by 21 to 29 percent relative to today’s vehicles and in 2025 by 31 to 37 percent. Table H.1 shows the improvements estimated for SI engines attributable to these approaches. The NRC hydrogen report also quotes studies by Heywood and colleagues at Massachusetts Institute of Technology (MIT) on the fuel efficiency of lightduty vehicles (Weiss et al., 2000; Heywood, 2007; Kasseris and Heywood, 2007; Kromer and Heywood, 2007). The fuel economy improvements noted in the MIT work result from changes to the engines and transmissions and appropriate reductions in vehicle weight. The MIT work assumes that the improvements are aimed entirely at reducing fuel consumption. Table H.2 shows the improvements in fuel economy compared to a 2005 SI engine vehicle that MIT estimates could be achieved by 2030, although the NRC hydrogen committee assumed that these levels of fuel economy would not be available as quickly.

TABLE H.1 Potential Reductions in Fuel Consumption (gallons per mile) for Spark-Ignition Vehicles Expected from Advances in Conventional Vehicle Technology by Category, Projected to 2025

 

2006-2015 (%)

2016-2025 (%)

Engine and transmission

12-16

18-22

Weight, drag, and tire loss reduction

6-9

10-13

Accessories

2-3

3-4

Intelligent start-stop

3-4

3-4

NOTE: Values for 2016-2025 include those of 2006-2015.

SOURCE: Duleep (2007).

Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×

TABLE H.2 Comparison of Projected Improvements in Vehicle Fuel Consumption from Advances in Conventional Vehicle Technology

 

Fuel Consumption (L/100 km)

 

Relative to 2005 Gasolinea

Relative to 2030 Gasolinea

Relative to 2005 Gasolineb

Relative to 2030 Gasolineb

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 the potential for hybrids outlined in Kromer and Heywood, it concluded that advances in hybrid technology are more likely to lower the cost of battery packs than to increase fuel economy significantly. This would increase their appeal to consumers relative to conventional vehicles and, thus, their market share (Kromer and Heywood, 2007). To simplify the analysis in the hydrogen report, the NRC hydrogen committee assumed that hybrids reduce fuel consumption a constant 29 percent annually relative to conventional vehicles, which also improve each year. This value is within the range of the potential for power split hybrids in the present report.

Thus, the NRC hydrogen committee judged that hybrid electric vehicles could, if focused on vehicle efficiency, consistently reduce fuel consumption 29 percent relative to comparable evolutionary internal combustion engine vehicles (ICEVs). Although this judgment is conservative compared to that of Kromer and Heywood, it still leads to a 60-mpg average for new spark-ignition hybrids by 2050. This means that hybrid technologies will have reached their greatest fuel consumption reductions by 2009 and that future improvements in hybrid vehicle fuel economy would be primarily attributable to the same technologies that reduce fuel consumption in conventional vehicles. Thus, hybrid vehicles reduce fuel consumption by 2.6 percent per year from 2010 through 2025, 1.7 percent per year in 2025-2035, and 0.5 percent per year between 2035 and 2050, the same as do evolutionary ICEVs.

PLUG-IN HYBRID ELECTRIC REPORT

After the publication of the NRC report Transitions to Alternative Transportation Technologies—A Focus on Hydrogen (NRC, 2008), the U.S. Department of Energy asked the Committee on Assessment of Resource Needs for Fuel Cell and Hydrogen Technologies to expand its analysis to include plug-in hybrid electric vehicles. The committee reconvened to examine the issues associated with PHEVs and wrote Transitions to Alternative Transportation Technologies—Plug-in Hybrid Electric Vehicles (referred to here as the PHEV report) to that additional task (NRC, 2009).

In accordance with the committee’s statement of task, the PHEV report does the following:

  • Reviews the current and projected status of PHEV technologies.

  • Considers the factors that will affect how rapidly PHEVs would enter the marketplace, including the interface with the electric transmission and distribution system.

  • Determines a maximum practical penetration rate for PHEVs consistent with the time frame of the 2008 Hydrogen Report and other factors considered in that report.

  • Incorporates PHEVs into the models used in the 2008 Hydrogen Report to estimate the costs and impacts on petroleum consumption and carbon dioxide (CO2) emissions.

As in this report, the PHEV report considered two types of PHEVs, a PHEV10 with an all-electric range of 10 miles and a PHEV40 with an all-electric range of 40 miles. Both reports use the same architectures as this committee, which include a spark-ignited internal combustion engine, two electrical machines, power electronics, and a Li-ion battery. Only the first task relates to our report, and comparing the two, it is necessary to separate the current technology status and the projections. The assessment of current technologies in the PHEV report is in close agreement with the assessment of this committee. Both discuss the different battery chemistries and the advantages and problems of each and point out how PHEVs differ from batteries for

Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×

HEVs, because the critical parameter is the energy available as opposed to the power needs. The discussion of power electronics and motors and generators within the PHEV report again generally parallels what is in this report. There are some differences in terms of the technological needs. For example, the PHEV report assumes that liquid cooling is assumed to be required for the PHEV40 battery packs whereas this report assumes air cooling will be sufficient.

The PHEV report was required to project and analyze the technology costs to 2050, while this report stopped at 2025. The methodology used is similar, and in both cases the costs were built up by adding the costs of the new components needed compared to an internal combustion engine vehicle. Costs were deducted for components such as engine simplification and the elimination of the transmission. The information was obtained from OEMs and suppliers in a similar way. For the PHEV10 the cost estimates in this report are within 5 percent of those in the PHEV report and within 3 percent for the 2020 to 2030 time frame. For the PHEV 40 the committee’s costs are significantly lower: by 45 percent for current costs and 42 percent for the 2020 to 2030 time frame. In view of the uncertainties of actual costs and how these would translate as retail price equivalents, the difference can be attributed to a difference in professional judgment.

A more difficult question is the rate at which the cost of the battery will come down, and what makes projections even harder is the injection of a substantial amount of capital by the administration and the enthusiasm of investors. Basically there are two ways of looking at future cost declines:

  • People making these very large investments in both vehicles and lithium ion batteries must expect the market to take off. Since the success of vehicle electrification depends on reductions in the price of battery by factors of two or three, investors and the administration must be optimistic that large cost reductions will occur.

  • A more pessimistic perspective is that lithium ion is a well-developed technology with billions of individual cells being produced.

How much improvement can one realistically expect in the 10-year horizon of the report? Both reports take a fairly conservative viewpoint in terms of the cost reductions of batteries over time and, taking into account developments in the last year, both reports may turn out to be overly conservative.

AEF ENERGY EFFICIENCY PANEL REPORT

The America’s Energy Future Energy Efficiency Panel examined the technical potential for reducing energy demand by improving efficiency in transportation, lighting, heating, cooling, and industrial processes using existing technologies, technologies developed but not yet widely utilized, and prospective technologies. In its report, Real Prospects for Energy Efficiency in the United States (NAS-NAE-NRC, 2010), the panel estimated the current contributions and future potential of existing technologies. In addition, the energy efficiency panel estimated the potential for new technologies that could begin to be commercially deployed in the next decade, the associated impacts of these technologies, and the projected costs per unit of reduction in energy demand. The panel’s work on light-duty vehicles is summarized in the following sections.

Gasoline SI Engine

Gasoline SI engine efficiency improvements contemplated by the NRC energy efficiency panel included engine friction reduction, smart cooling systems, variable valve timing (VVT), two- and three-step variable valve lift (VVL), cylinder deactivation, direct injection (DI), and turbocharging with engine downsizing. Most of these are already in low-volume production, and all could be deployed in large volumes in the next decade. In 15 to 20 years, technologies such as camless valve actuation, continuous variable valve lift (CVVL), and homogeneous-charge compression ignition (HCCI) could be deployed. The conclusions hoped for in connection with the deployment of camless valve actuation and HCCI are more optimistic than those anticipated for fuel cells in this report. The NRC energy efficiency panel survey shows the above technologies have the potential to reduce vehicle fuel consumption by 10 to 15 percent by 2020 and by an additional 15 to 20 percent by 2030 (EEA, 2007; Kasseris and Heywood, 2007; Ricardo, Inc., 2008; and NRC, 2008a).

Diesel CI Engine

Owing to high compression ratios and reduced pumping losses, turbocharged diesel engines offer a 20 to 25 percent efficiency advantage over gasoline SI engines when adjusted for the higher energy density of diesel fuel. The primary efficiency improvements in CI engines are likely to come from increased power density, improved engine system management, more sophisticated fuel injection systems, and improved combustion processes. New exhaust after-treatment technologies are emerging that reduce emissions of particulate matter and oxides of nitrogen to levels comparable to those of SI engines. One challenge for diesel engines noted by the NRC energy efficiency panel is the added costs and fuel economy penalties associated with the aftertreatment systems for reducing these emissions (Bandivadekar et al., 2008; Johnson, 2008; Ricardo, Inc., 2008).

Gasoline Hybrid Electric Vehicle

The primary efficiency benefits of a gasoline hybrid electric vehicle (HEV) noted by the NRC energy efficiency panel are realized by eliminating idling, including regenerative braking, downsizing the engine, and operating at more efficient engine conditions than current SI engines.

Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×

The NRC energy efficiency panel classifies hybrids on how well their electric motor and generator function. Belt-driven starter-generator systems eliminate engine idle to reduce fuel consumption by 4 to 6 percent. Integrated starter-generator systems that recover energy from regenerative braking, along with the start-stop function, can achieve a fuel consumption reduction of 10 to 12 percent. A parallel full hybrid with power assist, such as Honda’s integrated motor assist system, can reduce fuel consumption by more than 20 to 25 percent, whereas more complex systems using two motors such as 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 efficient than an equivalent gasoline hybrid, which translates to a 20 percent lower diesel fuel consumption when greater fuel density is factored in. A diesel HEV would be significantly more expensive than a gasoline HEV.

Vehicle Technologies and Transmission Improvements

The NRC energy efficiency panel notes that reducing the vehicle weight by 10 percent is commonly thought to reduce fuel consumption by 5 to 7 percent when accompanied by appropriate engine downsizing to maintain constant performance. Preliminary vehicle simulation results suggest that the relative benefits of weight reduction may be smaller for some types of hybrid vehicles (An and Santini, 2004; Wohlecker et al., 2007). In a conventional vehicle the energy used to accelerate the mass is mostly dissipated in the brakes, while in a hybrid a significant fraction of this braking energy is recovered, sent back to the battery, and reused. Thus weight reduction in hybrid vehicles has a much smaller effect on reducing fuel consumption than such reduction in non-hybrid vehicles. Additional weight reduction can be achieved by vehicle redesign and downsizing as well as by substituting lighter-weight materials in vehicle construction, For example, downsizing a passenger car by one EPA sizeclass can reduce vehicle weight by approximately 10 percent (Cheah et al., 2007). Additional sources of fuel consumption benefits noted by the NRC energy efficiency panel are from improvements in tires. A recent NRC report on tires and passenger vehicle fuel economy (NRC, 2006) agrees with estimates in the literature (Schuring and Futamura, 1990) that the vehicle fuel consumption will be reduced by 1 or 2 percent for a reduction of 0.001 in the coefficient of rolling resistance of passenger tires—equivalent to a 10 percent reduction in overall rolling resistance. The NRC energy efficiency panel also discussed transmission efficiency improvements likely in the next 10 to 20 years through an increase in the number of gears and through improvements in bearings, gears, sealing elements, and the hydraulic system. Table H.3 lists the efficiency improvements considered by the NRC energy efficiency panel that can be expected from different transmission systems in this time frame. Note that while a continuously variable transmission (CVT) allows the

TABLE H.3 Expected Transmission System Efficiency Improvements

Transmission

Efficiency (%)

Current automatic transmission (4- and 5-speed)

84-89

Automatic transmission (6- or 7-speed)

93-95

Dual-clutch transmission (wet clutch)

86-94

Dual-clutch transmission (dry clutch)

90-95

Continuously variable transmission

87-90

SOURCE: NAS-NAE-NRC (2010), quoting Ricardo, Inc. (2008) and EEA (2007).

engine to operate near its maximum efficiency, the current estimates of CVT efficiency are lower than the corresponding efficiencies of 6- or 7-speed automatic transmissions. CVTs have been in low-volume production for well over a decade.

Summary and Costs of Potential Light-Duty Vehicle Efficiency Improvements

Table H.4 shows plausible levels of petroleum reduction potential through vehicle technology improvements estimated by the NRC energy efficiency panel. The NRC energy efficiency panel developed its estimates from a number of sources (An and Santini, 2004; Wohlecker et al., 2007; Cheah et al., 2007; NPC, 2007; and NRC, 2004). The estimates shown in Table H.4 assume that vehicle size and performance, such as the power-to-weight ratio and acceleration, are kept constant at today’s levels. The evolutionary improvements briefly outlined above and discussed in more detail in the NRC energy efficiency panel report can reduce the fuel consumption of a gasoline ICE vehicle by up to 35 percent in the next 25 years. The diesel engine currently offers a 20 percent reduction in fuel consumption over a gasoline engine and, while the diesel engine will continue to evolve, the gap between gasoline and diesel vehicle fuel consumption is likely to narrow to a 15 percent improvement. Hybrid vehicles (including PHEVs) have a greater potential for improvement and can deliver deeper reductions in vehicle fuel consumption, although they continue to depend on petroleum (or alternative liquid fuels, such as biofuels). Battery electric vehicles (BEVs) and fuel cell vehicles (FCVs) are two longer-term technologies.

The cost estimates developed by the NRC energy efficiency panel shown in Table H.4 represent the approximate incremental retail price of future vehicle systems, including emissions control costs, compared to a 2005 baseline gasoline ICE vehicle (NHTSA, 2007; EEA, 2007; Bandivadekar et al., 2008). The first column shown is for a midsize car; the second column is for a typical pickup truck or SUV. These retail prices are based on the costs associated with producing a vehicle at the manufacturing plant gate. To account for distribution costs and manufacturer and dealer profit margins, production costs were multiplied by a factor of

Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×

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

Propulsion System

Petroleum Consumption (gasoline equivalent)

Incremental Retail Price (2007 dollars)

Relative to Current Gasoline ICE

Relative to 2035 Gasoline 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).

1.4 to provide representative retail price estimates (Evans, 2008). The timescales indicated for these future technology vehicles are not precise. The rate of price reduction will depend on the deployment rate (Bandivadekar et al., 2008; Evans, 2008).

The results in Table H.4 show that alternative powertrains such as improved gasoline and diesel engines and hybrids entering the fleet today cost from 10 percent to 30 percent more than a current gasoline vehicle. This price difference is estimated to drop to 5 percent to 15 percent in the midterm future. Longer-term options such as plug-in hybrid and FCVs are estimated to cost between 25 and 30 percent more than a future gasoline vehicle. Battery electric vehicles with standard vehicle performance and size remain costly, approaching double the cost of a future gasoline vehicle. A more plausible market opportunity for BEVs is small city cars with reduced range. However, these also will need significantly improved battery performance and battery costs to become competitive.

Based on the estimates in Table H.4, the NRC energy efficiency panel concludes that evolutionary improvements in gasoline ICE vehicles are likely to prove the most costeffective way to reduce petroleum consumption. Since these vehicles will be sold in large quantities in the near term, it is critical that their efficiency improvements are directed toward reducing fuel consumption. While the current hybrids appear less competitive than a comparable diesel vehicle, they are likely to become more cost competitive over time. PHEVs, BEVs, and FCVs appear to be more costly alternatives for reducing petroleum consumption and greenhouse gas emissions. Among these three technologies, PHEVs are likely to become available in the near to midterm, whereas BEVs and FCVs are mid- to long-term alternatives.

BIBLIOGRAPHY

An, F., and D. Santini. 2004. Mass impacts on fuel economies of conventional vs. hybrid electric vehicles. SAE Technical Paper 2004-01-0572. SAE International, Warrendale, Pa.

An, F., J.M. DeCicco, and M.H. Ross. 2001. Assessing the Fuel Economy Potential of Light-Duty Vehicles. SAE International, Warrendale, Pa.

Bandivadekar, A.P. 2008. Evaluating the Impact of Advanced Vehicle and Fuel Technologies in the U.S. Light-Duty Vehicle Fleet. Ph.D. thesis. MIT Engineering Systems Division, Cambridge, Mass.

Bandivadekar, A., K. Bodek, L. Cheah, C. Evans, T. Groode, J. Heywood, E. Kasseris, K. Kromer, and M. Weiss. 2008. On the Road in 2035: Reducing Transportation’s Petroleum Consumption and GHG Emissions. Massachusetts Institute of Technology (MIT) Laboratory for Energy and the Environment, Cambridge, Mass. July.

Cheah L., C. Evans, A. Bandivadekar, and J. Heywood. 2007. Factor of Two: Halving the Fuel Consumption of New U.S. Automobiles by 2035. LFEE Report 2007-04 RP. MIT Laboratory for Energy and the Environment. Cambridge, Mass: Massachusetts Institute of Technology. Available at http://web.mit.edu/sloan-auto-lab/research/beforeh2/files/cheah_factorTwo.pdf.

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Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×

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Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×
Page 181
Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×
Page 182
Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×
Page 183
Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×
Page 184
Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×
Page 185
Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×
Page 186
Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×
Page 187
Suggested Citation:"Appendix H:Other NRC Assessments of Benefits, Costs, and Readiness of Fuel Economy Technologies." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
×
Page 188
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Various combinations of commercially available technologies could greatly reduce fuel consumption in passenger cars, sport-utility vehicles, minivans, and other light-duty vehicles without compromising vehicle performance or safety. Assessment of Technologies for Improving Light Duty Vehicle Fuel Economy estimates the potential fuel savings and costs to consumers of available technology combinations for three types of engines: spark-ignition gasoline, compression-ignition diesel, and hybrid.

According to its estimates, adopting the full combination of improved technologies in medium and large cars and pickup trucks with spark-ignition engines could reduce fuel consumption by 29 percent at an additional cost of $2,200 to the consumer. Replacing spark-ignition engines with diesel engines and components would yield fuel savings of about 37 percent at an added cost of approximately $5,900 per vehicle, and replacing spark-ignition engines with hybrid engines and components would reduce fuel consumption by 43 percent at an increase of $6,000 per vehicle.

The book focuses on fuel consumption--the amount of fuel consumed in a given driving distance--because energy savings are directly related to the amount of fuel used. In contrast, fuel economy measures how far a vehicle will travel with a gallon of fuel. Because fuel consumption data indicate money saved on fuel purchases and reductions in carbon dioxide emissions, the book finds that vehicle stickers should provide consumers with fuel consumption data in addition to fuel economy information.

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