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5 Fuel Strategy Throughout the development of the automobile, engine and fuel advancements have been closely linked. The performance and emissions of the sophisticated power plants in current automobiles are critically dependent on the widespread availability of fuels that are tailored specifically for them. Automobile manufacturers and fuel suppliers have a common bond that is crucial to their business success as they must both please the same customer. Historically, this marketplace interdependence and performance linkage (e.g., the phaseout of lead in gasoline) have meant that engine and fuel changes had to be carefully coordinated to maintain customer satisfaction. The PNGV Goal 3 does not deal explicitly with secondary interactions, and the program initially focused exclusively on the vehicle. Although this shortcoming was noted by the committee in previous reports, no consensus by the PNGV members has been reached on weighing trade-offs between the energy consumed or emissions produced by the vehicle and the energy consumed or emissions occasioned by fuel processing and distribution. However, the critical role of the transportation fuel supply infrastructure has been acknowledged by PNGV now that fuel cells and CIDI engines have emerged as primary power-plant concepts (see Appendix F). Recent concerns about reducing fine particulate emissions from CIDI engines have brought the fuel issue into sharp focus. (The relationship between CIDI engine development and fuel developments is discussed in the section on Internal Combustion Reciprocating Engines in Chapter 2.) POTENTIAL FUEL MODIFICATIONS AND BENEFITS Many examples could be cited showing the close links between automotive engines and fuels. The performance and durability of spark-ignition engines are
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critically dependent on fuel octane rating; diesel engines are similarly dependent on fuel cetane ratings. Many other fuel characteristics, determined by the hydrocarbon mixture, are also important for proper engine operation over a wide range of ambient temperatures. Both exhaust and evaporative emissions are affected by fuel composition, and, in some geographical locations, special "reformulated" fuels have been mandated to reduce emissions. In addition to modifications of basic fuel compositions, additives have been introduced to ensure satisfactory performance, for instance, to improve storage characteristics or reduce the formation of engine deposits. For the PNGV program, the greatest uncertainty about the CIDI engine meeting its performance targets is associated with emissions, both NOx and particulates. One way to reduce particulates in the exhaust is to lower the sulfur content of the fuel. As particulate emissions standards become more stringent, lower fuel sulfur levels will almost certainly be required, as well as other measures to control particulate emissions. Lower sulfur content will also be necessary if a petroleum fuel is used as the feedstock for an onboard reformer for a fuel cell, and lower sulfur levels will be beneficial for NOx treatment technologies. Reducing sulfur content increases the complexity and cost of refining processing. The magnitude of the increase will depend, among other things, on the sulfur content of the crude oil being refined. Nevertheless, a fuel with low sulfur content could be introduced in much less time than a completely new fuel. Another way to produce low-sulfur fuel is to start with natural gas and synthesize a liquid fuel through the Fischer-Tropsch process. Natural gas is also the starting point for producing DME, a fuel with the potential to reduce both NOx and particulate levels in CIDI engines. The PNGV program is in the process of testing these and other types of fuel in CIDI engines. Because engine performance may vary with different fuels, joint development and evaluation by the transportation fuel and automobile industries will be important. The potential and time frame for making these fuels widely available must also be assessed. Fuel cells require hydrogen with low (ppm) concentration levels of CO and sulfur compounds to function efficiently. To avoid energy losses associated with an onboard reformer, the widespread availability of hydrogen will be a critical factor in the practicality of using fuel cells as energy converters. One possible option would be to produce hydrogen in large-scale plants at central locations and distribute it in pipelines. Another would be to convert hydrocarbon fuels into hydrogen at local fueling stations. Substantial energy losses and emissions can occur at various points in the process of making hydrogen available for automotive fuel cells. Sensible trade-offs for this fuel and power plant combination will require that the entire system, from the wellhead to the vehicle wheels, be analyzed. However, trade-offs would require specific criteria, such as reduced petroleum consumption or total energy expended, in addition to the vehicle energy consumption goal of PNGV.
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FUEL INDUSTRY Petroleum is an extremely versatile raw material, and petroleum refinery processes produce a wide variety of products used in many different industries. Refineries vary the proportion and composition of each product to suit market needs, and the economic success of each business entity in the industry depends largely on producing an optimum output mix of products from each refinery. Changing the fuel requirements for new cars will present a major problem for refineries because gasoline generally represents a high proportion of their output. In addition, petroleum refining is a highly capital intensive business, and it generally takes a long time to implement a major change. The fuel distribution system is also very extensive and complex, and changes are difficult to make and require a long time to implement. If a new automobile requires a unique fuel, both the manufacturer and the transportation fuels industry will be faced with a difficult dilemma. The mobility of the car will be severely restricted if the new fuel is not distributed widely. It must be available even in remote locations. If the availability of the fuel is limited, the car will have limited sales to the general public. At the same time, it would not be economical for fuel suppliers to provide ubiquitous distribution for the initially small number of new cars that will require the new fuel. This problem has limited the success of the government-encouraged ''alternative fuel" (methanol, ethanol, natural gas) vehicle programs, and it will continue to prevent the introduction of cars that require radically different fuels unless it is recognized and solved in some creative way. Even the widespread distribution of a new diesel fuel suited to automobiles would be a significant problem in the United States. Another important characteristic of the transportation fuels industry is that it consists of a large number of companies that vary widely in size, location of facilities, product mix, type of crude oil available, and many other significant factors. Also, it is very common for the product streams from different refineries and even different companies to become mixed at some point in the distribution system. Any significant change in automotive fuel will require a common product specification for all companies. However, this requirement may have widely different economic effects and may make different technical demands on each company. For some, the change may be accommodated easily, but for others the change may spell disaster. Differences in the composition of the crude oil available to different companies could magnify the difficulties of making the change. The intimate connection between vehicles and fuels has also drawn attention abroad. In Europe, energy companies, vehicle manufacturers, and legislatures have formed a European Auto Oil Program to determine vehicle emission controls for 2000 and 2005, as well as new legislation on fuel quality (Jones, 1997). This program is based on three core principles, namely, linking new legislation to air quality targets, looking at the whole vehicle-fuel system, and choosing the most cost-effective options.
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In September 1996, Japan launched the Japan Clean Air Program in cooperation with the Ministry of International Trade and Industry, the Petroleum Association of Japan, and the Japan Automobile Manufacturers' Association. Program objectives include: clarification of mid- to long-term strategies for automotive and fuels technologies that will reduce environmental loads to as low as can reasonably be achieved research into the effects of automobile and fuel technologies on vehicle emissions the development of the next generation of clean automobile and fuel technologies the development of cost-effective automotive and fuel technology measures to improve air quality PNGV should evaluate the European and Japanese programs that involve the transportation fuels industry when designing an appropriate integrated approach for the United States. CONCLUSIONS A widespread supply of a properly tailored fuel is critical to the success of any automotive power plant. A new power plant typically will operate optimally only if it is supplied with fuel tailored to its needs. If future automobiles are expected to require a fuel that is significantly different from the fuels now in use, extensive investigations of the feasibility, economics, and environmental impact associated with its production and distribution should be undertaken early in the development process. A major change in the fuel system infrastructure will require an even longer lead time. If a sequence of changes is anticipated by the PNGV program, the economics of the industries involved should be studied carefully. A study may indicate, for example, that only one major change will be economically feasible for the foreseeable future. If so, the choice of automobile power plants will be restricted to a sequence that is compatible with a common fuel. PNGV must recognize the tight linkage between the fuel producers and the automobile industry in order for the contemplated changes to be implemented successfully. To increase the PNGV's likelihood of success, a partnership (similar to the PNGV) between the U.S. government and the key automotive fuel producers should be considered. RECOMMENDATIONS Recommendation. The PNGV should propose ways to involve the transportation fuels industry in a partnership with the government to help achieve PNGV goals.
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Recommendation. PNGV's choices of energy conversion technologies should take full account of the implications for fuel development, supply, and distribution (infrastructure), as well as the economics and timing required to ensure the widespread availability of the fuel. Recommendation. The overall societal goals of the PNGV program should be clarified to include potential secondary energy and emissions effects.
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