3
Evaluations of Individual Technology Areas

The committee's assessment of the individual technology areas in the OAAT R&D plan and related recommendations are presented in this chapter. The order of presentation follows the sequence in the plan. Following a brief introduction to each technology area, the committee has commented on the strengths and weaknesses of the proposed R&D and has recommended improvements, as appropriate. The recommendations address not only the technical content of the plan, but also the clarity and consistency of the presentation.

Vehicle Systems

The Vehicle Systems section of the plan attempts to define the requirements for subsystems of the overall vehicle system necessary to meet the OAAT goals and objectives. The proposed approach involves computer modeling of the overall vehicle system, based on the development and validation of subsystem models incorporated into the overall vehicle system models. The approach also involves the design and development of complete test-bed vehicle systems for validating system models, demonstrating that vehicle performance objectives can be met, and validating subsystem and component technologies.

Comments

The vehicle systems area is crucial to the overall plan and deserves the prominent position it is given in the presentation. Systems analyses are necessary for configuring a vehicle to meet performance objectives. They are also necessary for setting priorities among technologies as a basis for allocating resources and



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--> 3 Evaluations of Individual Technology Areas The committee's assessment of the individual technology areas in the OAAT R&D plan and related recommendations are presented in this chapter. The order of presentation follows the sequence in the plan. Following a brief introduction to each technology area, the committee has commented on the strengths and weaknesses of the proposed R&D and has recommended improvements, as appropriate. The recommendations address not only the technical content of the plan, but also the clarity and consistency of the presentation. Vehicle Systems The Vehicle Systems section of the plan attempts to define the requirements for subsystems of the overall vehicle system necessary to meet the OAAT goals and objectives. The proposed approach involves computer modeling of the overall vehicle system, based on the development and validation of subsystem models incorporated into the overall vehicle system models. The approach also involves the design and development of complete test-bed vehicle systems for validating system models, demonstrating that vehicle performance objectives can be met, and validating subsystem and component technologies. Comments The vehicle systems area is crucial to the overall plan and deserves the prominent position it is given in the presentation. Systems analyses are necessary for configuring a vehicle to meet performance objectives. They are also necessary for setting priorities among technologies as a basis for allocating resources and

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--> selecting technologies, as well as for making Go/No Go decisions. In FY 1997, 31 percent of the OAAT budget ($38.85 million) was allocated for vehicle systems. The committee was not able to determine how much of the vehicle systems budget is devoted to systems analysis and how much to hardware development. The PNGV program devotes approximately $2.5 million each year to systems analysis (NRC, 1997). The committee believes that, at the present stage of development, systems analysis and supporting validation (if they can be provided quickly) are among the most important activities described in the plan because the results are needed to support decisions about future directions for technology development. The allocation of funds should reflect the crucial importance of systems analysis. In the committee's judgment, the technical tasks and milestones for the vehicle systems area are well thought out and appropriately directed toward modeling, simulation, and validating hardware for the complete vehicle. Nevertheless, these tasks and milestones are incomplete because they focus almost exclusively on fuel economy targets (50 mpg, 80 mpg, and 100 mpg) and pay little attention to costs, emissions, and other targets. Costs, emissions, acceleration, noise, vibration and harshness, drivability, safety, aerodynamics, rolling resistance, reliability, accessory loads (which can have a large impact on overall power requirements), and other criteria must also be considered in the optimization of a vehicle or in a decision to terminate research. Cost, in particular, could be considered a trade-off with societal benefits, or even with fuel economy, if the trade-offs were consistent with the goals and objectives of the plan. The plan should clarify how these trade-offs, as well as factors other than fuel economy, would be included in the analyses. More complex models will be required for these analyses than the very simplified models described in the technical approach to vehicle systems. Unfortunately, the plan devotes so much space to the status and targets of the PNGV vehicle systems technology that the OAAT plan is somewhat neglected. In the discussion of technical barriers, too, the real barriers to system integration are given less attention than subsystem barriers. The presentation of the vehicle systems R&D plan suggests that the focus is on propulsion systems, with less consideration given to other systems and components. For example, the proposed approach focuses on advanced engines, does not even mention fuel cells or electric batteries, and does not include fuel type as a primary factor in vehicle system design. The transition from first generation to second generation test-bed vehicles, which aims to ensure that only the most cost-effective integrated systems are developed, is not clearly described. The description of the vehicle systems R&D does not clarify whether the OAAT plans to focus on hybrid or conventional vehicle configurations. In contrast to conventional power trains, which have a single power source, hybrid power trains have a primary power source and a secondary power source that provides onboard energy storage. With a hybrid configuration, the primary

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--> energy converter can be smaller than in a conventional vehicle and can operate at loads and speeds that optimize efficiency, independent of the vehicle's immediate needs. In addition, a significant portion of the kinetic energy can be recovered as the vehicle decelerates. Regenerative braking is mentioned in the plan, but no strategy for overcoming related barriers is identified. In addition, the costs and benefits of regenerative braking, as opposed to alternative approaches to improving fuel efficiency (such as lightweight materials), are not addressed. The decision to focus on either a hybrid or nonhybrid vehicle is a systems issue that should be addressed in the vehicle systems section of the plan. The development of advanced power plants depends on this decision, but most power plant development described in the plan appears to be oriented toward a hybrid vehicle. In the committee's judgment, conventional (nonhybrid) vehicles should not be excluded at this time, particularly in light of the cost constraints described in the OAAT goal (advanced technology vehicles will have to be competitively priced compared with conventional vehicles.) The need for two power sources in a hybrid vehicle is likely to increase the overall cost and complexity of the power plant compared to conventional power plants. The increased complexity raises concerns about reliability because there are more possibilities of design flaws and failures. The committee urges OAAT to develop systems analysis tools to support decisions regarding vehicle configuration, including the decision to focus on hybrid or conventional power trains. Background information presented orally to the committee provided a much clearer picture of OAAT's plans in the area of vehicle systems than the written description in the plan. Incorporating the information provided by the DOE staff in its verbal presentations would greatly enhance the vehicle systems section in the plan. Recommendations Recommendation. The OAAT plan should emphasize the development of improved systems analysis tools that incorporate all factors relevant to (1) configuring the vehicle and making trade-off decisions; (2) setting priorities for resource allocation and technology selection; and (3) supporting Go/No Go decisions. Funding for systems analysis should reflect its overall importance to OAAT's R&D effort. Recommendation. The plan should include a thorough analysis of the trade-offs between hybrid and conventional (nonhybrid) vehicle configurations, including the relative reliability of hybrid and nonhybrid systems. Recommendation. The written presentation of the section on vehicle systems should be revised to include more background information.

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--> Advanced Engines The focus of the OAAT R&D plan for advanced engines is on CIDI (compression-ignition direct-injection) and gas turbine engines. Some work on spark-ignited, lean-burn engines is included but is slated to end in 1999. Industry is expected to continue work on the development of spark-ignited engine technology. Compression-Ignition Direct-Injection Engines The OAAT plan for R&D on advanced automotive piston engines involves working with the U.S. automotive industry to solve the major technical barriers associated with the CIDI engine. The major focus is on reducing emissions without compromising efficiency. Other technical objectives include increasing specific power by making the engine lighter. If the CIDI engine does not meet Environmental Protection Agency (EPA) emissions standards, it would have to be eliminated from further consideration for advanced technology vehicles. One area of activity in the OAAT plan encompasses several cooperative research and development agreements (CRADAs) between national laboratories and industry on oxides of nitrogen (NOx ) catalysts and nonthermal plasma technologies. CRADAs include the development of sensors and controls to measure and control emissions. Technologies for controlling particulates, fundamentals of exhaust gas recirculation (EGR), the development of CIDI models, and R&D on fuel systems are also being pursued. A second area of activity on CIDI engines described in the OAAT plan is R&D funded under the Hybrid Propulsion System Development Program, which was initiated by DOE with Ford in 1993 and with Chrysler in 1996. This program is focused on building and testing small displacement, lightweight, turbocharged, direct-injection engines for parallel hybrid propulsion systems.1 Ford is working with the FEV Engine Technology FEV is responsible for engineering the top end (i.e., cylinder head, Corporation to design and develop a 1.2-liter, four-cylinder engine. ports, piston cup design, and EGR) and the combustion system. Ford is responsible for the bottom end of the engine (i.e., cylinder block, crank train, sleeves, connecting rods, oil and water pumps, starter, and alternator), as well as for after-treatment. The first Ford/FEV development engine was on the test stand in Aachen, Germany, in the summer of 1997, and five technologies have been selected for further development.2 Work will focus on three areas, emissions 1   In a parallel hybrid propulsion system, the engine supplies some power directly to the drive wheels through a mechanical transmission, which is supplemented by electrical machines and an electrical power source. In a series hybrid propulsion system, all of the engine power is transmitted to the drive wheels through electric machines. 2   The following technologies were chosen for development: high pressure, common rail, fuel injection system; variable geometry, turbocharged boosting system; aluminum engine material; re-entrant bowl, swirl-supported combustion system; and active, lean NOx catalyst after-treatment.

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--> control; noise, vibration and harshness; and power density and engine weight. Chrysler is working with the Detroit Diesel Corporation to develop a three-cylinder engine, which is at the detailed design stage. The engine technologies being developed by FEV/Ford and Chrysler/Detroit Diesel may be suitable for conventional vehicle drivetrains, as well as for hybrid systems. Under the Hybrid Propulsion System Development Program, and aside from the CIDI effort, OAAT is also funding some work on a Stirling engine3 at General Motors and Stirling Thermal Motors for a series hybrid system. In this case, General Motors is supporting the hardware development, and OAAT is funding only the vehicle systems analysis. A third area of CIDI R&D within DOE—but outside of OAAT—is a major ongoing project within the OHVT (Office of Heavy Vehicle Technologies) directed toward the development of diesel engines for light trucks, sport utility vehicles, and heavy-duty vehicles. Industry participants are Caterpillar, Cummins, and Detroit Diesel. OAAT coordinates and co-sponsors cross-cutting projects with OHVT. Comments The committee believes that the development of a CIDI diesel engine is important to meeting the goal articulated in the OAAT plan. The CIDI engine could be used in a wide range of light-duty vehicles, assuming emissions standards; noise, vibration, and harshness goals; and targets for power density, specific power, and cost can be met as a result of R&D by government and industry. The marketability of the CIDI engine will be strongly influenced by the price and availability of both gasoline and diesel fuel. Fuel prices will be affected by any necessary modifications, such as sulfur removal, an increase in cetane number, or a reduction in aromatic content. Thus, engine and fuels development should not be treated independently. One aspect of the OAAT plan that needs to be clarified is the basis for the technical targets for the performance of CIDI diesel engines. Targets for peak efficiency, peak power, specific power, emissions, and power density are given in the vehicle systems section. More detailed performance targets, as well as cost targets, are given in the discussion of R&D on advanced automotive piston engines. But neither the basis for the targets nor the relationship between the two sets of targets is clear. For example, it is not clear whether the ''peak efficiency'' in the discussion of vehicle systems corresponds to "best brake thermal efficiency" or "best full-load thermal efficiency" in the discussion of advanced 3   The Stirling engine is an external combustion, reciprocating piston engine that is typically very quiet and relatively vibration free. It has been used successfully for stationary solar-to-electricity energy conversion and for some submarine and satellite applications (NRC, 1997).

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--> engines. It is also not clear which, if any, of these efficiencies correspond to the efficiency used to generate the design space for achieving the 80 mpg target. In other words, if the goals are met, where will the CIDI engine option fall in the design space and what will the corresponding requirements be for mass reduction and regenerative braking? The objectives for the CIDI engine program are to validate NOx emission levels of 0.3 grams/mile (g/mile), emissions of particulate matter of 0.05 g/mile,4 and to be cost competitive, although the targets do not appear to call for reductions in engine costs. The technical targets call for substantial improvements in specific power and durability, and the technical barriers list "cost" and "operational shortcomings (acceleration, odor, and noise, vibration, and harshness)," in addition to emissions, but the technical tasks appear to address only the problem of emissions. The Executive Summary states that the plan includes light vehicles, i.e., automobiles and light trucks (pickups, minivans, and sport utility vehicles) under 8,500 lb. GVW. The committee found, however, that the programs in the OAAT plan are directed almost exclusively toward automobiles, although in the case of CIDI engines, light trucks might be the easiest market to penetrate. If present trends continue, light trucks will dominate the market sometime between 2004 and 2008 (NRC, 1992; DOE, 1996), and much of the OAAT enabling R&D might be applicable to these vehicles. As the committee discovered, OHVT has a program directed toward the sport utility market. Even though this program is not covered in the OAAT plan, it could be described in a background discussion that would put the OAAT program in a broader context. A better description of how R&D funded by OHVT and R&D outside the government will complement the OAAT program would also be helpful. The distinction between government and private sector roles in R&D on CIDI engines is of concern to the committee. Many of the CIDI engine technical tasks in the OAAT plan—for example, R&D on CIDI fuel systems, spark-ignited combustion, advanced integrated emission control, and technology validation—are already being pursued by industry independently. Therefore, it is not clear to the committee why the government should be a partner in these activities. The plan should distinguish between government's role in facilitating R&D and industry's role in the final development of a marketable product. The need to develop an after-treatment system to control emissions of NOx , particulate matter, hydrocarbons, and carbon monoxide, which the plan identifies as the most important breakthrough technology required to make CIDI diesel engines competitive with spark-ignited engines, is a case in point. The after-treatment system will be technically sophisticated, involving sensors, controls, catalysts, and 4   The newly announced emissions level of "down to 0.01 g/mile" for particulate matter will be a major challenge for the CIDI program, as well as a potential challenge for advanced spark-ignition engines.

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--> advanced materials to support complex physical and chemical processes. The research to achieve this breakthrough is high risk, particularly if the cost targets are to be met, but has a high potential payoff. The committee found no evidence in the plan of a major, directed effort to synthesize particulate traps, reducing and oxidizing catalysts, plasmas, and fuel additives into a complete emission control system. This is an area where the government, as a partner, should insist on a systems approach to planning R&D. A clear delineation should be established between the required research and the ultimate development and production of a product, and the OAAT should fund only the generic research, which includes systems research as well as component research. The ultimate development and production of a practical system should be done by industry in a competitive environment. The exploratory research for CIDI engines described in the plan does not cover the fundamentals of after-treatment, which are very complex when combined into a system. This is an example of the lack of systems-level planning in OAAT's R&D program on CIDI engines. The major materials obstacle to meeting the weight reduction goals for a CIDI engine is the lack of a castable material that has many of the characteristics of grey cast iron but is substantially stronger. The goal of weight reduction is clearly defined in the PNGV plan but not in the OAAT plan. No clear research directions are defined in the OAAT plan for making the engine lighter, thereby increasing its specific power. Nor is there a discussion of the candidate materials, such as compacted cast iron, spheroidized cast iron, and aluminum alloys, that might meet the requirements for castability, damping, recycling, and cost, as well as weight reduction. Recommendations Recommendation. The plan should describe the OHVT sport utility program and other government and industry CIDI programs and explain how they complement OAAT's R&D on CIDI engines. Recommendation. The plan should give a better explanation of how the OAAT program for the CIDI diesel engine will be managed in anticipation of a continuing market shift from automobiles to pickups, vans, and sport utility vehicles. Recommendation. The OAAT plan should clearly identify CIDI engine projects that primarily involve generic research, which should be funded by government, and projects that involve incremental improvements in technology or are closely tied to the development of commercial products, which should be left to private industry. Recommendation. The plan should include a brief description of the sources of and bases for the technical performance targets for CIDI diesel engines and should clarify the various ways the term "efficiency" is used.

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--> Recommendation. The OAAT should ensure that its program includes a major engineering effort to integrate particulate traps, reducing and oxidizing catalysts, plasmas, and fuel additives, as well as advanced materials, sensors, and controls, into a complete after-treatment system to control emissions. The program should include both hardware development and modeling. Recommendation. The plan should define the materials and manufacturing approaches to be used in CIDI engine designs that aim to reduce weight and increase specific power. Turbines Automotive-scale (40 to 60 Kw) gas-turbine power unit technology is being developed as a power plant option for use in hybrid vehicles. Gas turbines have the advantage of producing low emissions (except for NOx ), and they can be used with different fuels. The technical goal of OAAT R&D on gas turbines is to develop an efficiency of 38 percent or more at 25 percent load for a hybrid vehicle fuel economy of 80 miles per gallon equivalent (mpge). The stated objectives are to validate ceramic components by 1999 and to validate 80 mpge in a hybrid vehicle by 2002. Four major technical barriers are identified: efficiency, especially at part load; cost, especially in ceramic component fabrication; durability and reliability, especially for ceramic components; and NOx emissions, especially for cold starts and transients. The goal of the materials R&D program related to gas turbines is the development of durable, high temperature, high strength ceramic materials and associated manufacturing technologies. Comments Gas turbine engines have characteristics that can potentially contribute to the OAAT goal of developing propulsion systems for light vehicles with improved fuel economy, low emissions, and alternative fuel capability. More than a half-century of development, primarily for commercial and military aircraft, has resulted in a mature technology and gas turbine engines with power-to-weight ratios, emission characteristics, and fuel flexibility superior to current spark-ignited and compression-ignition automotive engines. The peak thermal efficiency of these larger gas turbine engines also exceeds the thermal efficiency of spark-ignited engines and is comparable to the best current compression-ignition engines. However, these efficiencies have not been demonstrated in smaller engines (less than 100 Kw) that are compatible with automotive requirements. These efficiencies appear to be extremely difficult to achieve because of the problems of developing small aerodynamic turbomachinery components and the necessity for high turbine inlet temperatures (NRC, 1997). Aircraft and military gas turbines are also extremely expensive and do not have operational-envelope characteristics compatible with automotive driving-cycle requirements. Specifically, part-

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--> load efficiency in aircraft and military gas turbine engines is typically poor; response time is slow compared to automotive needs; and the rotational speed of appropriately sized engines is at least an order of magnitude greater than automotive spark-ignited and compression-ignition engines, which puts severe performance demands on mechanical transmissions and electric machines. Aircraft-type gas turbine engines achieve high thermal efficiencies largely by operating at high turbine inlet temperatures (1,200°C to 1,400°C). The high temperatures are possible because of the combination of high-temperature super-alloys and intricate air cooling passages internal to the turbine blades. Both of these features are much too expensive for automotive engines. Therefore, the approach proposed in the OAAT R&D plan is to use cast ceramic turbine components that can withstand the high turbine temperatures. The development of a technology for producing high quality, low cost ceramic turbine components will be necessary, but not sufficient, for producing automotive propulsion systems that meet OAAT objectives. One area of concern, for example, is that engines that operate at high temperatures might produce unacceptable levels of NOx emissions. Even if the high temperatures can be reached, the target efficiencies can only be achieved if very effective regenerators or recuperators are used to recover waste heat. High rotational speeds and slow response times essentially dictate that a gas turbine engine in an automobile will require a hybrid configuration, specifically a series hybrid configuration. Consequently, a high-speed, high-efficiency generator (or alternator) must be developed as an integral part of the gas turbine engine. Six of the seven technical barriers to the development of gas turbines and engine system materials are entirely or primarily associated with ceramic components, and seven of the eight technical tasks are entirely or primarily associated with the development and manufacture of ceramic components. The implication is that overcoming problems with ceramics would all but eliminate the technical barriers to a hybrid vehicle turbine. However, this inference may not be justified because there may be other technical barriers, such as: high efficiency, low cost compressors and burners high efficiency, high speed, low cost generators or alternators low cost control systems low cost means of powering accessories low cost, highly effective, lightweight, low volume regenerators or recuperators a means of providing high engine efficiency at low engine load the minimization or elimination of high fuel consumption under no-load conditions (idling or decelerating) casing materials, tolerance requirements, balance, bearings, start-up and shutdown systems, sound generation issues relating to fatigue and engine life in an automotive application

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--> It is also likely that, if the target combustion temperatures are achieved, NOx production will emerge as a major technical barrier. In the committee's judgment, the technical barriers identified in the plan and the tasks to resolve them are generally reasonable and appropriate. Unfortunately, the goals and objectives for turbines do not mention cost, which is included in the technical targets for the turbine but not for the ceramic components. The dates for meeting the technical targets and milestones must surely be questionable, given that the technical approach to low cost ceramic components has not been defined and that breakthroughs appear to be necessary. Other important technical areas are not addressed, raising the possibility that even if a ceramic turbine could be developed, the engine could still be far from successful. Recommendations Recommendation. The technical approach to producing low cost, durable, and reliable ceramic components should be better defined in terms of specific technical (as opposed to administrative) paths. Recommendation. The plan should specify major technical barriers to the development of automotive gas turbines besides the development of high temperature, low cost ceramic components. The following objectives and tasks should be added to the plan: address other areas where costs may be unacceptably high, such as compressors, burners, control systems, bearings, and housings establish a more definitive approach to achieving very high efficiencies at 25 percent power establish a more definitive approach to reducing NOx levels, if necessitated by increased combustion temperatures define an approach to developing a high efficiency, low cost alternator establish criteria for acceptable engine life Fuel Cells Fuel cells are being investigated as a potential alternative to the internal combustion engine in automobiles. Fuel cell vehicles offer the potential of higher energy efficiency than vehicles powered by internal combustion engines because they use a near isothermal electrochemical reaction as opposed to a combustion process. Like combustion engines, fuel cells can use a variety of hydrogen-rich fuels (hydrogen, methanol, gasoline, ethanol, and other hydrocarbons) from fossil or renewable sources. If an onboard fuel reformer is used, there could be emissions of sulfur and carbon monoxide (CO), although these are likely to be very low because the fuel cell/reformer system contains catalysts that are degraded by

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--> sulfur and CO. Issues associated with the production of a clean fuel remain to be resolved. The use of any hydrocarbon fuel in a fuel cell will result in emissions of carbon dioxide (CO2 ). Thus, hydrogen fuel cells have zero or near zero undesirable emissions, although with a reformer generating hydrogen from a carbon-containing fuel, they have greenhouse gas emissions (CO2 ). Proton exchange membrane (PEM) fuel cells are the current technology of choice for road vehicles. They offer the potential for low cost mass production, as well as higher power density and more rapid start-up time (because of low-temperature operation) than other types of fuel cells. Nevertheless, the power density and start-up time for PEM fuel cells are poor when compared to internal combustion engines. The OAAT program (like most other fuel cell vehicle development programs around the world) has focused on PEM technology (NRC, 1997). All fuel cells being considered for automotive applications require hydrogen fuel. Because a hydrogen infrastructure is not widely available, hydrogen must be produced from a readily available fuel source. Therefore, the OAAT program has focused primarily on a hydrocarbon fuel with an onboard fuel processor to convert it to a hydrogen-rich gas that can be used by the fuel cell. OAAT has also supported some research on onboard hydrogen storage and direct methanol fuel cells. In addition to research on fuels for fuel cells, the OAAT program supports research on fuel cell stack systems (the reduction of catalyst loadings, CO poisoning of catalysts, stack materials and manufacturing, thermal and water management, balance of plant integration), fuel processors (CO cleanup, system integration and efficiency, start-up and transient operation, thermal management), and hydrogen storage. In addition, OAAT supports R&D on integrated 50 KW fuel cells and fuel processor systems. Industry-led teams are developing three integrated automotive fuel cell power systems that run on hydrogen, methanol, and gasoline, respectively. Demonstrations of all three of these systems are scheduled in the next several years. Comments The committee identified four major strengths of the proposed fuel cell R&D program. First, the research priorities are focused on the most important technical issues: fuel cell stack performance, fuel cell component cost and manufacturing, fuel processor development, system integration, and hydrogen storage. Second, technical barriers are clearly identified, and the approaches to overcoming them are generally good. A detailed, cogent research program is set forth. Third, the program is keeping open the hydrogen option (by supporting studies on hydrogen storage) and is also supporting an ongoing small program with the Defense Advanced Research Projects Agency (DARPA) on direct methanol fuel cells. However, the main thrust of the OAAT program is the development of onboard fuel processors that operate on gasoline, methanol, ethanol, or natural gas. The OAAT program is well coordinated with the DOE Hydrogen Program, and in the committee's judgment, this coordination should be continued. Finally,

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--> Recommendations Recommendation. The technical objectives for power electronics and electric machines should explicitly include more reliable and environmentally rugged power electronics to meet automotive requirements. Consistent with these objectives, the list of technical barriers should be expanded to include the constraints on operating temperatures imposed by critical passive components, such as electrolytic capacitors. Recommendation. The technical barriers should be modified to specify the manufacturing limitations of current power electronics, which are at least as important as materials in driving up the costs of power converters. Recommendation. After an expert review within the power electronics community, the materials R&D plan, which is scheduled for completion at the end of 1997, should be incorporated into the master five-year plan. Recommendation. The OAAT, as a stakeholder in the multi-agency PEBB program, should ensure that more program resources are devoted to reducing the cost of power electronics. Advanced Automotive Materials Lightweight materials in the drivetrain, body, and chassis will be necessary for the OAAT to meet its goal of vehicle fuel economy. Although not all of the technical targets are specified in the systems analyses described in the plan, the weight reduction targets are well defined. Four areas are targeted, namely, a 50 percent weight reduction in both body and chassis, a 10 percent weight reduction in the hybrid power train (as it exists today), and a 55 percent weight reduction in the fuel system. Comments The timelines in the plan for the development of materials and materials processing technologies will require much more rapid progress than has been made in the past. Therefore, it would be useful if strategies were more clearly defined to provide some assurance that the goals might be achieved. Using aluminum and polymer matrix materials in sheet and body structures has been demonstrated, but only at very high costs and after long and extensive efforts. Strategies for producing high volume, low cost components made of these materials have not been identified. Consistent with its earlier comments about government and industry roles in R&D partnerships, the committee considers that the government involvement in advanced automotive materials development should be limited to

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--> generic research that supports innovative approaches to overcoming technical barriers. OAAT should not fund industry work on incremental improvements in materials technology. The strategy outlined in the plan for reducing the cost of light metals, aluminum (Al), magnesium (Mg), and titanium (Ti), does not appear to be well thought out. Considerable efforts over many decades by major metal producers, the Bureau of Mines, many universities, and others to improve methods and reduce costs have not resulted in breakthrough technologies for the production of light metals. The cost of a metal is governed by the cost to produce it from its ore.11 Iron (Fe) is a relatively low cost metal for three main reasons: it is abundant in nature; iron ores are rich in iron and easily beneficiated; and iron oxide can be reduced by carbon at relatively low temperatures (about 700°C). Light metals are generally found in the form of very stable oxides. Although aluminum is more abundant than iron in the earth's crust, aluminum ores are much more difficult to process. The free energy of formation of aluminum oxide is much greater than that of iron oxide, and as a result, reducing aluminum oxide by carbon requires temperatures near 2,000°C. Consequently, the aluminum reduction process is performed electrolytically and is much more costly than the reduction process for iron oxides. As a result, the cost per pound of aluminum ingot is roughly ten times the cost of pig iron. Mg and Ti are reasonably abundant in the earth's crust, although less abundant than Fe or Al, but their ores are low grade (Mg is mined from seawater in the United States) and reducing them to the metallic state is much more complex. Magnesium ores are processed electrolytically or using the Pidgeon process; the Kroll process is used to process Ti. The OAAT program goal is to produce a car that is 85 percent recyclable; present vehicles are about 80 percent recyclable. However, current vehicles contain substantial quantities of plain carbon steel and grey cast iron, materials that can be easily recycled and are eagerly sought as feedstock by mini-mills and foundries. If lightweight materials (high strength steels, Mg, Al, Ti, and composites) are used extensively in future vehicles, the recycling problems will be much more challenging. For the goal of 85 percent recyclability to be considered realistic, programs must be developed for the easy separation of components made from different materials and for recycling alloyed and polymer-based materials, all of which will be challenging tasks. 11   The energy requirements (and related costs) for recycling metals are much lower than for primary production. For example, steel requires about 31 gigajoule (GJ)/ton to produce and 8.7 GJ/ton to recycle. Comparable figures for aluminum are 270 GJ/ton for production and 16.5 GJ/ton for recycling. Although about 50 percent of steel and 40 percent of aluminum come from recycled materials, the supply of recycled materials is not sufficient to meet total demand. Thus the original cost of primary production is a major component of material cost, and efforts to reduce this cost must focus on the primary production process.

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--> Recommendations Recommendation. Strategies for making very rapid progress in materials development and processing technologies should be described in more detail to enhance their credibility. Recommendation. The proposed program to reduce the costs of light metals should be examined in terms of basic thermodynamic principles to establish a comparison with the cost of producing iron and iron alloys. Recommendation. A program should be defined to address the challenges of recycling vehicles that contain relatively large quantities of high strength steels, Mg, Al, Ti, and composites to meet the goal of 85 percent recyclability. Alternative Fuels The strategic plan of the OTT (Office of Transportation Technologies), and the supporting R&D by the OAAT, are intended to reduce transportation energy or fuel consumption in the United States, including petroleum consumption.12 Alternative fuels have the potential to displace substantial amounts of petroleum, as well as to improve fuel efficiency and lower emissions, if the cost barriers associated with vehicles, fuels, and infrastructure can be overcome. These cost barriers vary depending on the fuel, but none of the alternatives is competitive with today's gasoline or diesel fuel. In response to legislation, such as the Alternative Motor Fuels Act of 1988 and the Energy Policy Act of 1992, original equipment manufacturers have begun to produce vehicles that run on alternative fuel. At present, these vehicles account for only 0.1 to 0.2 percent of total highway fuel usage. The OAAT R&D plan for alternative fuels acknowledges that the commercialization of some alternative fuels has already begun; the plan is oriented toward technologies where further research or development is needed to remove critical barriers. The fuels under consideration in the plan are CNG (compressed natural gas), ethanol, and DME (dimethyl ether). Natural gas and ethanol have already been developed as alternatives to gasoline and diesel fuel, and commercial vehicles that can operate on these alternatives are already available. In contrast, technology for DME-fueled vehicles is relatively immature. Parallel to the efforts described in the OAAT plan, the OTT is conducting a fuels study to determine which fuels are most likely to be commercialized in the twenty-first century. This study, which is expected to be completed in 1998, will be used to prioritize future work by OTT. 12   ''Petroleum" is defined as conventional liquid fuels made from crude oil.

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--> Compressed Natural Gas Comments Using CNG in light-duty vehicles reduces petroleum consumption. Liquefied, as opposed to compressed, natural gas is better suited to heavy-duty vehicles. OAAT plans to develop technologies that will enable CNG vehicles to be "similar to" gasoline vehicles in cost, range, refueling convenience, safety, and acceptance level. Thus, in the committee's judgment, OAAT has correctly identified the existing shortfalls in CNG technology. A major strength of the proposed plan is the interactive R&D involving both the fuel and vehicle industries, as well as academia, which will be doing fundamental research. The main weaknesses of the plan relate to the ambitious objectives (300 mile vehicle range and 50 percent reduction in the cost of refueling stations) to be achieved within a short period of time and the relative priorities assigned to the technical barriers. Natural gas is one of the few alternative fuels that currently has an operating cost advantage over gasoline. This cost advantage is the primary driver for fleet operators to purchase CNG vehicles, although some, if not all, of the advantage would disappear if natural gas were taxed in the way gasoline is. Even today, the lower fuel cost only offsets the higher vehicle cost if the vehicle operates in a high mileage fleet. The average retail customer does not drive enough miles per year to offset the higher vehicle cost. One of the major barriers to retail customer acceptance of the CNG vehicle is the high initial cost of the vehicle, primarily because of the high cost of the fuel tanks. This cost would come down if the volume of production went up. The volume will remain small, however, until the retail market has been penetrated, which will only happen if there is adequate refueling infrastructure. The establishment of a low cost, widely available refueling infrastructure is unlikely because the cost of a CNG fast-fill refueling station is too high. The OAAT R&D plan estimates that the cost of a CNG refueling station is five times the cost of a gasoline facility. Therefore, even if the targeted 50 percent reduction in refueling station cost could be achieved through better compressor designs and materials and improvements in some of the other refueling technologies mentioned in the plan, the economic barrier to CNG market penetration would remain. The refueling infrastructure issue could be addressed by retail customers using small, slow-fill compressors to refuel vehicles in their garages overnight. However, there are significant safety concerns associated with this concept, and the capital cost of the equipment (several thousand dollars) would be difficult for the average retail customer to amortize. If the equipment were leased by the gas company to the customer, the equipment cost would be reflected in an increased fuel cost, and CNG would probably not be competitive with gasoline. Without the advantage of lower fuel cost, it is doubtful that customers would be interested in CNG-fueled vehicles. Therefore, in the committee's judgment, technical tasks

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--> that address the cost and reliability of CNG refueling should be given the highest priority in the OAAT plan. Without a substantial reduction in the cost of refueling infrastructure, the market for CNG vehicles will be too small to support the OTT fuel strategy plan. The increased use of CNG in light vehicles would reduce petroleum consumption but would not significantly reduce energy use. Therefore, the plan should state clearly that the CNG program is not aimed at 80 mpge fuel economy. Although natural gas is widely available, an increase in the use of CNG as a vehicle fuel in the United States would probably result in increased imports, as well as higher prices and higher road use taxes. Thus, the advantages of CNG in reducing petroleum consumption would be offset by increased imports and higher prices, and there would be very little reduction in overall energy use. Environmental issues associated with the use of CNG need to be considered from a broad perspective. CO2 emissions from CNG vehicles are lower than from equivalent gasoline vehicles (Leiby et al., 1996). However, increased methane emissions are associated with the CNG distribution system, and methane is a greenhouse gas with a higher temperature effect than CO2 . Thus the overall impact of CNG use on global climate change should be considered. The committee urges OAAT to adopt a systems perspective when addressing questions relating to the use of alternative fuels. Lean-burn combustion, in principle, can increase fuel efficiency, but the operating limits—such as air-to-fuel ratio—consistent with maintaining vehicle performance have not been defined. Fuel-lean operation would also increase NOx emissions. The current NOx catalyst depends on the presence of CO (carbon monoxide) for the reduction reaction. If an engine is operated fuel-lean, the amount of CO present is too low for the catalyst to work, and the NOx emissions are too high to meet current air quality standards. Consequently, CNG engines must be operated at stoichiometric air-to-fuel ratios. The plan should explain how a targeted 10 percent improvement in efficiency will produce a 150 percent increase in range, which is another target. If these targets are met by changing the design to increase the tank volume without decreasing vehicle cargo capacity, the proposed technical approach and costs should be described. The descriptions of technical tasks generally do not include descriptions of the technical approaches to overcoming barriers. Because safety is also identified as a concern, related work should be described, and work being conducted outside OAAT should be cited. The plan targets safety improvements that will make CNG as safe as, or safer than, reformulated gasoline but does not describe related technical approaches or tasks. Recommendations Recommendation. The priority of the technical barriers for CNG should be changed. The cost and reliability of fueling facilities and the related technical

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--> task should be given the highest priority. Substantial reductions in the cost of refueling facilities should be a major criterion for the 2001 Go/No Go decision to continue the development of CNG vehicles. Recommendation. Technical tasks relating to onboard fuel storage, especially the cost of fuel tanks and vehicle range, should remain in the plan and should be assigned second and third priorities, respectively. A detailed technical description of the technologies that might enable achievement of a 300-or 380-mile vehicle range should be included. Recommendation. The plan should address the issue of controlling NOx emissions in vehicles with more efficient, fuel-lean combustion. Recommendation. Technical approaches to safety concerns raised by the increased use of natural gas should be included in the plan. Recommendation. The plan should affirm the need for a systems approach, including life cycle analyses, to evaluate the trade-offs associated with the use of alternative fuels, such as CNG. Issues that should be addressed in a systems evaluation include the impact of the increased emissions of methane (a greenhouse gas) associated with natural gas vehicles and the related infrastructure. Ethanol Comments Ethanol is a renewable, nonpetroleum fuel. About 97 percent of all the ethanol produced in the United States today comes from ethylene derived from petroleum,13 so the use of ethanol from this source would have little effect on petroleum consumption or energy efficiency. However, ethanol can also be made from biomass and thus has the potential to reduce petroleum consumption and CO2 emissions, depending on the biomass source and production process. Methanol can also be a renewable fuel made from biomass, and the production process is less expensive than for ethanol. Neither methanol nor ethanol made from biomass, however, is cost competitive with alcohols produced in a chemical plant.14 Costs associated with ethanol use are being addressed by DOE's Office of Fuels Development and are not addressed in the OAAT R&D plan, which focuses on technical issues associated with ethanol-fueled vehicles. But the current 13   Most ethanol used for fuel is currently produced from biomass, but ethanol for chemical purposes is produced from ethylene. 14   Almost all of the methanol produced in the United States today is made from natural gas.

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--> federal subsidy for ethanol produced from biomass should be a consideration in the large scale use of ethanol. Because fuel subsidies and taxes are subject to adjustments that reflect changing public policy, analyses of alternative fuels should be based on real costs rather than prices as much as possible. The plan correctly states that a fully optimized, dedicated alcohol-fueled vehicle has the potential to increase fuel efficiency. High efficiency vehicles are being produced in Brazil, for example, where hydrous ethanol is widely available commercially. Use of hydrous rather than anhydrous ethanol reduces fuel costs because the fuel production process does not require a water-removal step. Evaporative emissions are not a problem for vehicles that use high levels of alcohol fuels. At present, dedicated alcohol vehicles are not being produced in the United States because of the lack of refueling stations for dedicated vehicles (there are only 35 ethanol and 65 methanol stations in the United States). Fuel-flexible vehicles, which are being produced in the United States, have lower performance and are less fuel efficient than vehicles fully optimized for a single alcohol fuel. The plan also correctly states that ethanol-fueled vehicles have problems with cold starts, which is attributed to low vapor pressure (ethanol has a vapor pressure of only 2.3 psi). No mention is made of the fact that ethanol, unlike gasoline, has a single boiling point (72°C). The ethanol vehicles presently being produced in the United States are designed to use E85 (85 volume percent ethanol and 15 volume percent gasoline, with a vapor pressure of about 6.9 psi). Although the cold start performance with E85 is better than with pure ethanol, it still does not meet the same specifications as gasoline.15 In the committee's judgment, further improvements in the cold start of E85 should be undertaken by the vehicle manufacturer. In general, the committee does not consider it appropriate for the OAAT to support the incremental improvement of ethanol-fueled vehicles, given that these vehicles are currently in production by at least two automotive manufacturers (Ford and Chrysler). Technologies for ethanol-fueled vehicles are well beyond the stage of precompetitive R&D. Because the OAAT plan for ethanol does not address innovative, high-risk approaches to making ethanol commercially competitive with gasoline, the committee sees no need for government funding of the proposed R&D. The plan states that the successful resolution of the cold start problem with E85 technology ''will allow research to progress to neat ethanol (E95)16 in the future, which would provide greater energy and emissions benefits." Almost a 15   The physical properties of methanol are better for cold starts (4.6 psi, with a boiling point of 65°C), and M85-fueled vehicles have met industry standards for cold starts (M85 consists of 85 percent methanol and 15 percent gasoline). 16   E95 is composed of 95 volume percent ethanol and 5 volume percent gasoline. The terminology used in the plan is confusing because E95 is variously referred to as "neat ethanol" and "near-neat ethanol." The committee prefers to avoid use of the term "neat," which can be confusing when discussing hydrous and anhydrous ethanol.

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--> of the efficiency gains and other high performance attributes of alcohol-gasoline mixtures can be achieved with a 50-50 mix, making the gains in changing from E85 to E95 negligible (Nichols et al., 1987). In fact, increasing the proportion of ethanol above 85 volume percent reduces the vapor pressure and aggravates the cold start problem. Therefore, in the committee's judgment, there is no justification for moving to E95. Recommendations Recommendation. The OAAT efforts related to ethanol-fueled vehicles should be eliminated from the R&D plan because these vehicles are already in production. In the event that legislative mandates require OAAT to continue some work on ethanol, further consideration of E95 should be eliminated from the plan because this fuel has little more to offer than E85, and it exacerbates the cold start problem. Dimethyl Ether Comments DME could be a good substitute for diesel fuel in compression-ignition engines; it has a high cetane number and inherently low particulate emissions. However, methanol also has inherently low particulate emissions, and DME is normally made from methanol. On the one hand, the additional processing step from methanol to DME increases the costs and requires more energy. On the other hand, DME has a higher volumetric energy density than methanol, and thus has advantages for onboard fuel storage, as well as for reducing the volume of liquid that has to be handled during fuel distribution. (DME is a liquid only when it is stored and distributed under pressure.) The committee suggests that the plan include a more detailed description of the advantages of DME over methanol and the trade-offs between the two fuels. The discussion should assume that methanol or DME fuels would be made from cheap natural gas from remote sources and shipped to the United States. It should also be noted that Detroit Diesel has already produced a methanol-fueled compression-ignition engine. The characteristics of DME are similar to those of propane, and therefore a DME distribution and refueling system is expected to be much like the system for propane or liquefied petroleum gas (LPG). Moderate fuel tank pressures would be required (nominally 160 psi for LPG) for onboard storage of DME as a liquid rather than as a gas. The plan acknowledges that the technologies for producing and using DME are in the very early research stage in the United States and that cost, reliability, durability, safety, and other performance parameters have not been well defined. OAAT plans to use some ongoing work at the OHVT (Office of Heavy Vehicle

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--> Technologies) and the Tank Automotive Command to help in its initial development of a fuel injection system for light-duty vehicles. The committee suggests that OAAT also take into account the results of work in progress on DME outside the United States. Even though technical barriers for DME cannot be defined, OAAT must provide some justification for including this fuel in the plan. The OAAT objectives in the Goal and Objectives section of the plan mention CNG and ethanol but not DME. The committee speculated that DME might be included under the objective that addresses "automotive technologies that use non-petroleum-based fuels that achieve zero emissions while obtaining 100 miles per gallon." If this is correct, OAAT must indicate how DME-fueled vehicles might achieve the OAAT objectives of 80 or 100 mpge. The committee noted that the reduction in incremental vehicle cost of $1,500 to $600 indicated in the technical targets for DME does not appear to meet the OAAT goal of a vehicle that is "competitive with conventional vehicles." Recommendation Recommendation. The plan should state that DME is made from methanol and should include an analysis of the technical and economic trade-offs between using methanol and DME (made from methanol) as compression-ignition engine fuels. Electric Vehicle Batteries The primary motivation for the EV is to improve urban air quality and reduce petroleum use. The large scale replacement of internal combustion engine powered vehicles by EVs would have a substantial impact on petroleum consumption because the electricity required to recharge the batteries would be supplied by central power stations, which (in the United States) use petroleum for only a small percentage of their total electricity production. The impact of EVs on total energy consumption is uncertain and would depend on the overall efficiency of the EV and its supply of electricity over the fuel cycle, from fuel source to EV recharging station. Increased demand for electricity from central power stations to power EVs could have adverse environmental effects. For example, coal-fired power plants produce air emissions, including greenhouse gases, as well as solid waste. EVs introduced into the market to date have not met with great success, primarily because of their high cost and the need to recharge them frequently, which restricts their range. The key to market success for the EV has always been battery technology. USABC has sponsored the development of nickel-metal hydride, sodium-sulfur, and lithium-ion battery technologies to meet mid-term (1997) goals. Meeting the long-term (2000) goals has focused on lithium-polymer technology. The OAAT R&D plan focuses on battery development, which is being conducted through USABC.

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--> Comments The background information in this section of the plan should explain that the long-term goals specified by the USABC in 1991 were revised in 1996 and that the revised goals are reflected in the plan. Given the important historical role of the USABC in EV battery development, it would be helpful for OAAT to explain and justify the proposed replacement of the USABC, which is expected to end in 2000, with an advanced battery initiative. Such programmatic changes can result in a loss of momentum. In the committee's judgment, the progress in the development of EV batteries is praiseworthy, and the new goals and technical tasks identified by the USABC seem to be appropriate, as does the division of goals into "mid-term" and "long-term" categories. However, to put the proposed R&D in context, a list of all the battery technologies investigated in the USABC program should be given, together with some explanation as to why certain technologies, such as sodium-sulfur, were dropped by USABC. The attention to safety and to the extensive testing of existing systems in the plan is appropriate. The USABC goals for EV batteries indicate a price of less than $150/kWh in the mid-term (1997) and less than $100/kWh (with a desired goal of $75/kWh) in the long term (2000). These prices assume an annual production of 10,000 units of 40 kWh each. However, the technical target in the plan for nickel-metal hydride batteries is $300/kWh for 20,000 units/year in 1997 and $150/kWh for 20,000 units/year for lithium-polymer batteries in 2000. The discrepancies between the USABC goals and the OAAT technical targets have to be explained. OAAT must also explain how these costs will make EVs competitive with conventional vehicles. In the committee's opinion, the target cost will be difficult to attain, and the proposed technical approach for reducing cost is not adequately defined ("have each developer conduct ... efforts to reduce production cost"). Some work being done on EV batteries is well under way and appears in the milestones as almost completed. OAAT should update the plan and include progress reports to date. It is not clear why safety and disposal appear in the same heading in the list of technical barriers for lithium-polymer batteries. If there is an implicit link between safety and disposal, it should be identified. The technical barriers for the lithium-polymer battery are formidable. For example, anode and cathode materials that will ensure stable capacity during battery cycle life are not available, and the chemical and electrochemical stability of the electrolyte are inadequate to support long cell life. The tasks that address the technical barriers are too vague to be meaningful. For example, unless safety issues involved in the disposal of lithium-polymer batteries are identified, the value of the related R&D cannot be properly evaluated. The section headed Materials Research consists of a single sentence referring to an exploratory technology research program. In the committee's judg-

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--> ment, this perfunctory treatment fails to reflect the importance of materials development, which is the focus of the technical tasks. If the research in question is to develop advanced materials beyond those addressed in the Advanced Automotive Materials section of the OAAT R&D plan, this should be explained. Recommendations Recommendation. The OAAT should describe its plans for the transition to a new program when the USABC program ends in 2000. Recommendation. The cost targets and technical approach to reducing the cost of EV batteries should be explained in more detail. Recommendation. The tasks for addressing the technical barriers of lithium-polymer batteries should be more specific, and the metrics for assessing progress should be stated. References Conway, B.E. 1991. Transition from "supercapacitor" to "battery" behavior in electrochemical energy storage. Journal of the Electrochemical Society 138(6):1539–1548. DOE (U.S. Department of Energy). 1996. Transportation Energy Data Book: Edition 16. Prepared by Oak Ridge National Laboratory for the U.S. Department of Energy under Contract No. DE-AC05-96OR22464. Washington, D.C.: DOE. IEEE (Institute of Electrical and Electronic Engineering). 1996. Proceedings of the Sixth International Seminar on Double-Layer Capacitors and Similar Energy Storage Devices. Deerfield Beach, Florida, December 9–11, 1996. New York: Institute of Electrical and Electronic Engineering. Leiby, P.N., D.L. Greene, and H. Vidas. 1996. Market potential and impacts of alternative fuel use in light-duty vehicles: a 2000/2010 analysis. DOE/PO-0042. Technical Report 14 in the Assessment of Costs and Benefits of Flexible and Alternative Fuel Use in the U.S. Transportation Sector. Washington, D.C.: Office of Policy, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy. NRC (National Research Council). 1992. Automotive Fuel Economy: How Far Should We Go? Energy Engineering Board, National Research Council. Washington, D.C.: National Academy Press. NRC. 1997. Review of the Research Program of the Partnership for a New Generation of Vehicles, Third Report. Board on Energy and Environmental Systems and Transportation Research Board. Washington, D.C.: National Academy Press. Nichols, R.J., S. Moulton, N. Sefer, and E.E. Ecklund. 1987. Options for the introduction of methanol as transportation fuel. Presented at the International Fuels and Lubricants Meeting, Toronto, Ontario, November 1987 (Society of Automotive Engineers paper no. 872166).