Copyright 1999 Federal Document Clearing House, Inc.
Federal Document Clearing House Congressional Testimony
October 05, 1999
SECTION: CAPITOL HILL HEARING TESTIMONY
LENGTH: 5547 words
HEADLINE:
TESTIMONY October 05, 1999 JAMES A. SPEAROT DIRECTOR GENERAL MOTORS RESEARCH AND
DEVELOPMENT CENTER HOUSE SCIENCE ENERGY AND ENVIRONMENT FUTURE
FUELS AND PETROLEUM SUPPLIES
BODY:
ADVANCED FUEL
TECHNOLOGY NEEDED FOR FUTURE VEHICLE PROPULSION SYSTEMS October 5, 1999
Testimony of James A. Spearot Director, Chemical and Environmental Sciences
Laboratory General Motors Research and Development Center Warren, Michigan On
Behalf of the Partnership for a New Generation of Vehicles Advanced Fuels Group
USCAR Written Testimony Customer demands, government regulations, and business
objectives have greatly impacted the design and development of automotive engine
technology during the past thirty years. With passage of the original Clean Air
Act and the introduction of early exhaust emissions control devices, the
development of engine technology transitioned from simply designing a "stand
alone" automotive component - the engine - to development of a complex electro-
mechanical system. These systems have four fundamental elements that work
collectively to provide our customers with the attributes they want from their
vehicle -- good driving performance, low emissions, and long-term durability
(low maintenance). The four elements that make up the system include 1) the base
engine, 2) the emissions control system, 3) the electronic controller with
associated programming, and 4) the fuel. In order to meet all customer
expectations and government requirements for fuel efficiency and emissions all
four components must be designed to be compatible. My testimony today will focus
on the types of advanced fuels that will be needed for future transportation in
the US, and the challenges that we face in bringing them to the marketplace. In
that regard, I will not address immediate needs and concerns, but rather the
changes in fuel composition and quality that will be required to enable future
vehicle propulsion technology, such as that being worked on in the
industry/government Partnership for a New Generation of Vehicles or PNGV. In
addition, this testimony will review the auto industry's expectation for fuel
compositions and sources well into the 21st century. Petroleum Fuel Technologies
Needed to Enable Future Propulsion Systems Future stringent emissions standards,
such as US Tier 11 and California LEV 2, coupled with goals for improving fuel
efficiency, will require very different engine technologies that are critically
dependent on the commercial availability of advanced fuel formulations. These
future fuels will need to be substantially different from the fuels currently
marketed. The development of optimum compositions and formulations of each fuel
will require additional research and evaluation, but several trends can be
identified now based on our understanding of the characteristics of each
advanced propulsion system. Future advanced technologies such as direct
injection engines and fuel cells are likely to be used in meeting future vehicle
emissions and fuel efficiency goals. Direct injection engines can provide 15 to
35 percent improvements in fuel efficiency, and fuel cells can provide even
greater gains at very low emissions levels. However, very clean fuels will be
required to allow the vehicle systems to achieve the maximum benefits to both
air quality and efficiency. As an example of how critically dependent these
advanced engine technologies are on advanced fuel formulations, the "lean NO,"
absorber catalysts, being investigated for use on gasoline- or
diesel-fueled direct injection engines, are very sensitive to the presence of
sulfur contaminants in the fuel. As little as 5 or 10 ppm of
fuel sulfur can render the catalyst inactive after only very
limited mileage. To regenerate such catalysts requires a complex and fuel
inefficient engine control strategy that reduces the fuel economy of such
advanced engines. For a fuel cell, both the reformer used to convert hydrocarbon
fuels into hydrogen and the fuel cell stack are permanently poisoned by
sulfur. All future propulsion systems currently envisioned
within the automobile industry will require near zero levels (< 10 ppm) of
sulfur. Spark-ignition, Direct Injection Engines In order to
provide improved vehicle fuel efficiency, most future internal combustion
engines will operate as lean as possible (excess air present for the amount of
fuel fed to the engine). Today, engines operate at stoichiornetric conditions
(air and fuel in correct chemical proportions for complete combustion) because
current exhaust emissions catalyst technology is capable of reducing emissions
to more than 98 percent of their uncontrolled value only under such conditions.
The technology referred to as spark-ignition, direct injection (SIDI) engines is
an example of the strategy of operating engines under lean air-fuel ratio
conditions for improved fuel efficiency. There is currently no known catalyst
technology that will provide sufficient NO,, emissions conversion capability
under very lean engine operating conditions to meet anticipated emissions
regulations for the life of the vehicle. Furthermore, the few catalyst
technologies that provide some conversion capability are extremely sensitive to
contaminants and poisons in the fuel. Commercial versions of this technology
that operate at moderately lean conditions have been marketed in Japan. One
reason that spark-ignition, direct injection engines can be sold in Japan is the
quality of fuel available in that market. The low level of
sulfur in Japanese gasoline (typically less
than 1 0 parts per million) allows the use of lean NO. catalysts as well as
reduces the formation of particulate emissions. Japanese
gasolines typically have more tightly controlled volatility
characteristics than US gasolines which permits both reduced
emissions and acceptable driveability. In addition, the hydrocarbon composition
of Japanese gasolines helps to limit the formation of
combustion chamber and injector deposits in such engines. SIDI engine operation
is extremely sensitive to the formation of such deposits, and both engine
maintenance requirements and customer satisfaction are improved when deposit
formation is limited. It is doubtful that SIDI engine technology can be
introduced into general markets in the US in view of anticipated emissions
regulations and the wide range in fuel properties available in different parts
of the country. Significant numbers of this fuel efficient engine technology
will only be marketed when there is a commercial source of very low
sulfur gasoline blended with tight controls on hydrocarbon
composition and volatility, and advanced additives to reduce combustion chamber
deposits. Compression-ignition, Direct Injection Engines Compression- ignition,
direct injection (CIDI) engines are predicted to provide even better fuel
efficiency than their spark ignition counterpart. The automobile
industry/government partnership, PNGV, is considering the use of advanced CIDI
engine technologies in hybrid vehicle configurations. However, unacceptable
levels of oxides of nitrogen and particulate emissions will result unless a
means of control is developed. As with SIDI engines, fuels containing high
levels of sulfur will limit the degree to which emissions can
be controlled in a CIDI engine. Sulfur is a direct contributor
to the amount of particulates produced by the engine in the form of sulfates
emitted with the exhaust. Sulfur also severely reduces the
efficiency and durability of lean NOx catalysts. The use of compression ignition
engine technology in the US that is compliant with future stringent emissions
standards will be prohibited by the current levels of sulfur in
commercial distillate fuels. The levels of aromatic hydrocarbons in diesel fuel
must also be reduced in order to limit the formation of particulates if CIDI
engines are to be commercially viable. Previous studies have shown a
relationship between higher aromatic concentration in the fuel and greater
exhaust particulate emissions. For substantial numbers of CIDI engines to be
used for light-duty vehicle applications in the future, an advanced form of
reformulated diesel fuel will be required to meet anticipated emissions
standards. Such a fuel will require very low sulfur
concentrations, reduced aromatic content, a possible oxygenate component, and
effective additives to improve the fuel's ability to lubricate mechanical
components within the fuel pump and injection system. Synthetic hydrocarbons
manufactured from natural gas using the Fischer- Tropsh process could also
provide benefits as blending components to reduce the emissions forming
potential of diesel fuels. Short of these fuel modifications, it is doubtful
that the considerable fuel efficiency benefits of compression ignition engines
will be available in the US. Fuel Cells The primary fuel for current fuel cell
system designs is hydrogen. Hydrogen fed to the fuel cell stack reacts with
oxygen within an electrochemical cell to produce electricity. Although oxygen is
readily available from intake air, the source of hydrogen to power a fuel cell
vehicle has been and continues to be a topic of intense research and
development. Assuming that the current fuel distribution infrastructure should
be maintained, it would be desirable to use petroleum-derived, liquid
hydrocarbon fuels as a source of hydrogen for fuel cells. There is currently
active research to determine if gasoline could be used in an
on-board reformer system to obtain hydrogen. Although this process has been
accomplished to a degree within a large laboratory apparatus, it is not known
whether the same process can be applied on a vehicle scale. It is clear,
however, that current commercial gasoline compositions do not
represent an optimum fuel formulation for present reformer designs. As opposed
to spark ignition engines, fuel cell reformers do not benefit from high- octane
gasoline. In fact, the addition of high-octane components is
counterproductive to the efficiency of the fuel cell system. The optimum fuel
will have as high a hydrogen-to-carbon ratio as possible to maximize the
efficiency of the system. Fuel reformers are catalytic systems that are also
adversely affected by the presence of sulfur in the fuel.
Current studies have suggested that the fuel for such systems will have to be
essentially "sulfur-free". The fuel reformer is also sensitive
to the formation of deposits. Although the optimum liquid petroleum fuel for
fuel cells is different in composition and properties from conventional
gasoline, there are specific refinery streams that are close in
composition to that which is needed. Thus, it is conceivable to envision a
special fuel produced by conventional refineries and distributed and sold along
side conventional gasoline and diesel fuels for use in fuel
cell vehicles. It is possible that the ideal hydrocarbon- based fuel cell fuel
will also be well suited for advanced CIDI engine technology Alternative Fuel
Options The preceding paragraphs on advanced engine technology fuel needs have
concentrated on the use of fuels derived from liquid petroleum sources. Given
the amount of capital invested in current refineries and liquid petroleum
distribution systems in the US, this focus on liquid hydrocarbons is justified.
It is important to note, however, that alternative fuels derived from natural
gas, biomass and solar sources could also be developed to support the needs of
such advanced engine technology. All alternative fuel options are currently more
expensive than those advanced fuels derived from petroleum. Thus in all cases,
the use of fuel alternatives would require substantial government incentives in
some form to create a market for such options. As with petroleum derived fuels,
alternative fuels would also have to meet the high quality specifications
outlined above, including very low sulfur and aromatic
hydrocarbon concentrations. To help identify potential candidates for
alternative fuels that might find use as energy sources for powering
transportation vehicles during the 21st century, it is useful to review those
attributes which automotive designers desire in any potential fuel. First the
fuel should have as high an energy density as possible for maximum range and
consumer convenience. It should have good combustion characteristics. That is,
the proper octane for spark ignition engines, and high "cetane" for compression
ignition engines. The fuel should have a low tendency for forming deposits
throughout the fuel, combustion, and emissions control systems. The fuel should
have no instantaneous or long- term effect on exhaust emissions control systems.
And finally, the fuel should have a reasonable cost. Within the context of these
general characteristics, the nature of a specific fuel depends greatly on the
engine technology in which it will be used. Each advanced engine technology has
several alternative fuel options that could be used to provide the required
source of energy during the next century. In the case of spark ignition engines,
the most promising fuels include: highly reformed gasoline
having virtually no sulfur and very low olefins and aromatic
hydrocarbons; alcohols derived from cellulose to help mitigate C02 concerns; or
a controlled specification natural gas. Hydrogen could play a role in powering
spark ignition engines, but only if a reasonably priced source of hydrogen can
be developed. This source of hydrogen should be renewable and create little
impact on global C02 generation to be of significant value. For compression
ignition engines, the most promising future fuels include: highly reformed
diesel fuel containing virtually no sulfur or aromatic
components; or possibly highly reformed diesel fuels blended with oxygenate
components developed to reduce particulate formation during the combustion
process. In addition, future fuels such as liquid hydrocarbons derived from
natural gas using the Fischer-Tropsh process, and alcohols derived from
cellulose could be used in advanced compression ignition engines. Finally for
fuel cell electric vehicles, the best alternatives include: high
hydrogen/carbon, zero sulfur refinery streams; synthetic
hydrocarbon blends derived from natural gas; methanol or as production, storage,
and distribution systems develop - renewable hydrogen. Summary and Conclusions
During the next century, the introduction of new vehicle powertrains and
propulsion systems will accelerate driven by the need for improved fuel economy
and reduced emissions around the world. World-class cars and trucks will require
world-class fuels. Government support is needed to help control fuel properties
and to provide fuel alternatives needed to enable advanced propulsion
technologies and improve engine emissions performance. In addition, support for
petroleum-based fuels with improved properties would help to stop the
devaluation of the emissions reduction potential that is currently designed into
every car and light truck on the road, and paid for by the American consumer.
LOAD-DATE: October 6, 1999 
