EPA-460/3-74-013-a
July 1974
CURRENT STATUS
OF
ALTERNATIVE AUTOMOTIVE
POWER SYSTEMS
AND FUELS
VOLUME I -
EXECUTIVE SUMMARY
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Mobile Source Air Pollution Control
Alternative Automotive Power Systems Division
Ann Arbor, Michigan 48105
-------
EPA-460/3-74-OU-a
CURRENT STATUS
OF
ALTERNATIVE AUTOMOTIVE
POWER SYSTEMS
AND FUELS
VOLUME I -
EXECUTIVE SUMMARY
Prepared by
The Environmental Programs Group
The Aerospace Corporation
El Segundo, California 90245
Contract No. 68-01-0417
EPA Project Officer: Graham Hagey
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Mobile Source Air Pollution Control
Alternative Automotive Power Systems Division
Ann Arbor, Michigan 48105
July 1974
-------
This report is issued by the Environmental Protection Agency, to report
technical data of interest to a limited number of readers. Copies of this
report are available free of charge to Federal employees, current contractors
and grantees, and non-profit organizations - as supplies permit - from the
Air Pollution Technical Information Center, Environmental Protection Agency,
Research Triangle Park, North Carolina 27711, or may be obtained, for a
nominal cost, from the National Technical Information Service, 5285 Port
Royal Road, Springfield, Virginia 22151.
This report was furnished to the U.S. Environmental Protection Agency
by the Aerospace Corporation, El Segundo, California, in fulfillment of
Contract No. 68-01-0417 and has been reviewed and approved for publication
by the Environmental Protection Agency. Approval does not signify that
the contents necessarily reflect the views and policies of the agency.
The material presented in this report may be based on an extrapolation of
the "State-of-the-art" . Each assumption must be carefully analyzed by
the reader to assure that it is acceptable for his purpose. Results and
conclusions should be viewed correspondingly. Mention of trade names
or commercial products does not constitute endorsement or recommendation
for use.
Publication No. EPA-460/3-74-013-a
11
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FOREWORD
This report, prepared by The Aerospace Corporation for the
Environmental Protection Agency (EPA), Alternative Automotive Power Sys-
tems Division, summarizes available nonproprietary information on the tech-
nological status of automotive power systems which are alternatives to the
conventional internal combustion engine, and the technological status of
nonpetroleum-based fuels derived from domestic sources which may have
application to future automotive vehicles.
The status of the technology reported herein is that exist-
ing at the end of 1973 with more recent data in selected areas. The
material presented is based principally upon the results of research and tech-
nology activities sponsored under the Alternative Automotive Power Systems
(AAPS) Program which was originated in 1970 and which is administered by
the Alternative Automotive Power Systems Division of EPA. Supplementary
data are included from programs sponsored by other government agencies
and by private industry. Additional information on technology and development
programs is known to the government but cannot be documented herein because
the data are proprietary.
One purpose that the AAPS Program serves is to provide a
basis of knowledge and perspective on what can and cannot be accomplished
with the use of alternative propulsion and fuels technology, and to disseminate
this information to Congress, Federal policy makers, industry, and the
public. Thus, the publication of information such as that contained herein is
in keeping with this element of the mission of the AAPS Program. This is the
first of a series of reports on alternatives that are intended to be published
annually.
The results of this study are presented in four volumes and
three main topical areas:
Volume I. Executive Summary
Volume II. Alternative Automotive Engines
-111-
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Volume in. Alternative Nonpetroleum-Based Automotive
Fuels
Volume IV. Electric and Hybrid Power Systems
Volume I, the Executive Summary, presents a concise view of important find-
ings and conclusions for all three topical areas. Thus, an overview of the
study results may be obtained by reading Volume I only. Volumes II, III,
and IV contain detailed, comprehensive discussions of each topical area and
are therefore of interest primarily to the technical specialist. Each of these
three volumes also contains Highlights and Summary sections pertaining to
the topical area covered in the volume.
- iv-
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ACKNOWLEDGMENTS
Appreciation is acknowledged for the guidance and assistance
provided by Mr. Graham Hagey of the Environmental Protection Agency (EPA),
Alternative Automotive Power Systems (AAPS) Division, who served as EPA
Project Officer for this study. Appreciation is also extended to staff members
of the AAPS Division, to other EPA divisions, to personnel of various govern-
ment agencies, and to those in industry and the academic community who
supplied reference material and reviewed the contents of this report. In
particular, the information provided by Exxon Research and Engineering
Company and the Institute of Gas Technology during their contractual study
efforts for EPA has been a valuable contribution to sections of the report on
alternative nonpetroleum-based fuels.
The many technical personnel of The Aerospace Corporation
•who made valuable contributions to the effort performed under this contract
are acknowledged in the specific volumes to which they contributed.
Merrill G. Hinton, Director
Office of Mobile Source Pollution
D. E. Lapedes/ Study Manager
Toru lura, Associate Group Directors^
Environmental Programs Group
Directorate
jh Mej/tzer, Group Director
fironmental Prograrg^fl/Group
'Directorate
-v-
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INTRODUCTION
In the first 20 years of this century, many different power
systems were in competition as an automotive powerplant. The three major
competitors were battery-powered electric systems, steam engines (Rankine
cycle), and spark ignition internal combustion engines (Otto cycle). Many
production versions of each type of system were on the market and at least
one manufacturer offered versions of all three systems (apparently more
uncertain of the final outcome than other manufacturers). It is well known
that the Otto cycle system eventually won out. Although occasional attempts
have been made over the last 50 years to bring out new versions of electric
vehicles and steam engines, none have yet offered serious competition to the
Otto cycle engine and, in fact, few have been marketed.
Perhaps the most significant past effort to develop an alterna-
tive powerplant for passenger cars was that sponsored by the Chrysler Cor-
poration on gas turbines. After nearly 20 years of research and a consider-
able investment of manpower and resources, this effort culminated in a
50-car fleet of gas turbine-powered vehicles tested by consumers throughout
the United States starting in 1964. Following evaluation of these tests, a
corporate decision was made not to proceed with turbine production and it
appeared that the Otto cycle engine would continue its dominant position as
the powerplant for automobiles.
However, events would soon overtake any complacency on the
part of those satisfied with maintaining the status quo. By the late 1960's,
the public was becoming much more aware of the rapidly deteriorating air
quality in large urban areas in this country. At the same time, the Congress
grew increasingly impatient with existing regulatory programs for control of
automobile-caused air pollution. Exhaust emissions from the internal com-
bustion engine in automobiles had long been singled out as the primary cause
of smog and more stringent control of emissions from this source appeared
•warranted.
-1-
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It was late in 1969 when members of the President's Office of
Science and Technology, then headed by Dr. Lee DuBridge, expressed their
environmental concern to the President. It was stated that because of the
automobile's significant contribution to the nation's deteriorating air quality,
the exhaust emission standards required in future years--through the end of
this century--might have to be so stringent as to preclude the clean up of the
conventional Otto cycle engine. To alleviate the potential impact of such
events and to provide assurance to the nation that technologies relating to
other types of power systems would be available, if needed, a Federal pro-
gram of research and technology development was recommended.
The President announced the program in his Message on the
Environment early in 1970. That program, called the Alternative Automotive
Power Systems (AAPS) Program, is managed by the Environmental Protec-
tion Agency (EPA) in Ann Arbor, Michigan. The program was focused initially
on power systems that offered the potential of being inherently clean compared
with the conventional Otto cycle engine. In 1972 the program scope was broad-
ened and energy efficiency was elevated to equal importance with low auto-
mobile exhaust emissions. Investigations on the use of alternative fuels (non-
petroleum derived) were also included at that time.
The present report concerns the developments in alternative
powerplants as related to the conventional Otto cycle engine, and in alterna-
tive nonpetroleum-based fuels as related to petroleum-derived gasoline. The
objective of the report is to summarize the available information on the tech-
nological status of alternatives for future automotive vehicles. As such, then,
it serves to document the results from the many past and present activities of
the AAPS Program, as well as to provide similar information from programs
sponsored by other government agencies and by private industry.
Originally called the Advanced Automotive Power Systems Program.
-2-
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The significant findings with regard to technological status are
summarized herein under the category headings of:
• Alternative Automotive Heat Engines
• Alternative Nonpetroleum-Based Automotive Fuels
• Electric and Hybrid Power Systems.
-3-
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ALTERNATIVE AUTOMOTIVE HEAT ENGINES
As used herein the term 'heat engine1 applies to the category
of engines in which heat is converted in some form to work in order to pro-
vide power to the wheels of a vehicle. The heat engine then is the prime
mover. The source of heat is generally the combustion of a fuel in air.
Several different types of heat engines for use in automobiles
have demonstrated the ability to provide desired power levels while simul-
taneously offering the potential for major reductions in exhaust emissions
when contrasted with the conventional spark ignition engine. In some cases,
an engine has been characterized as having the potential to meet the original
1975 Federal emission standards [hydrocarbons (HC) =0.41 grams per mile
(gm/mi), carbon monoxide (CO) =3.4 gm/mi, oxides of nitrogen (NO ) =
12 X
3. 1 gm/mi)] or the original ' 1976 Federal emission standards (HC =
0.41 gm/mi, CO =3.4 gm/mi, NO =0.4 gm/mi) without extensive after-
treatment or add-on devices. Each engine, however, has certain design and
performance deficiencies that remain to be overcome (e.g., excessive size,
high manufacturing cost, prolonged startup time). Recently, the concern
over conservation of energy resources has prompted additional effort in the
areas of reduction in engine fuel consumption and verification of flexibility
in operation with a wide range of possible fuels. This is exemplified, as
noted previously, by early modifications within the EPA AAPS Program to
stress fuel consumption reduction as well as achievement of emission levels
consistent with Federal standards.
Interim standards with relaxed requirements are now in effect.
that emission goals for the AAPS Program were set at one-half the
original 1976 standards to ensure compliance under production and in-service
conditions.
-5-
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DEVELOPMENT STATUS OF ALTERNATIVE HEAT ENGINES
The following highlights summarize the status of development
work on alternative engines investigated in recent years. The engines re-
viewed are the gas turbine, Rankine cycle, Stirling cycle, Diesel cycle,
Wankel (and other rotary piston designs), and Otto cycle (using stratified
charge combustion). These engine types are in various stages of develop-
ment, ranging from redesign of engines under limited production to early
research and mid-term development efforts on engines at least eight to ten
years from full production (if placed in a production program status).
Gas Turbine Engines
1. Until recently, the exhaust emissions of automotive-type gas turbine
engines have been typified as characteristically low in unburned
hydrocarbons and carbon monoxide, but with NOX levels too high
to permit attainment of the original 1976 Federal emission stan-
dard of 0.4 gm/mi. For example, Chrysler's sixth-generation engine
installed in an intermediate-size vehicle (Figure 1) has NOX emissions
of about 2. 2 gm/mi over the Federal Emissions Test Driving Cycle. A
summary tabulation of emissions from gas turbine combustors and
systems appears in Table 1.
2. As part of the AAPS Program, Solar, a Division of International
Harvester, has recently developed a new gas turbine combustion sys-
tem that, based on steady-state test data, is calculated to be capable
of meeting the original 1976 Federal emission standards and is close
to meeting the AAPS Program goals (one-half the level of the original
standards). Additional development is required to perfect the com-
bustor control system and to validate meeting program goals with
transient operation of the engine over the Federal Emissions Test Driv-
ing Cycle.
3. Reflecting similar recent advancements, a General Motors-sponsored
program resulted in an experimental 225-horsepower gas turbine engine
installed in a car meeting the original 1976 Federal emission standards.
Complete details concerning engine design and operation are not
available.
4. Estimated high production cost is another factor inhibiting the imple-
mentation of the automotive gas turbine engine. Other problems involve
the need for improvements in noise level, durability, acceleration lag,
and fuel economy. These problems are being investigated by Chrysler
under a $6. 5 million EPA contract awarded in December 1972 for the
-6-
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Figure 1. Chrysler 150-hp Gas Turbine Engine, Vehicle Installation
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Table 1. Gas Turbine Exhaust Emission Data Over the
Federal Emissions Test Driving Cycle
Engine /Manufacturer
a. Conventional Combustors
United Aircraft Research
Laboratories RGSS-6
United Aircraft Research
Laboratories SSS-10
Chrysler sixth-generation
engine
Williams Research/
WR26/AMC Hornet
Williams Research/
131Q/Volkswagen
b. Advanced Combustors
Solar
General Motors 225 HP
Regenerative Engine
AiResearch
United Aircraft of Canada
c. Clean Air Act Requirements
Emissions (gm/mi)
CO
0. 53
1.86
3.99
7.43
6.92
4. 5
3.34
2. 4
1.6
3.64
3.4
HC
0. 15
0. 31
-0.26
0.62
0.72
0. 34
0. 11
0.015
0.67
0. 49
0. 41
NO
X
2. 72
1.03
2.21
2.8
2. 5
1.81
0.34
0. 315
0.44
0. 52
0. 4
Remarks
Calculated values over simulated
Federal Driving Cycle, based on
emission data from GM engine
GT-309.
Calculated values over simulated
Federal Driving Cycle, based on
emission data from GM engine
T-56.
1975 Federal Test Procedure
emissions corrected (background
level subtracted from measured
values).
Cold start /1975 Federal Test
Hot start (Procedure
1972 Federal Test Procedure.
Calculated values for simulated
Federal Driving Cycle, based on
advanced combustor data.
Experimental test bed engine,
chassis dynamometer test with
5,000-lbcar, 1975 Federal Test
Procedure.
Calculated values for simulated
Federal Driving Cycle, for recu-
perated engine with 10 percent
bypass .
Calculated values over simulated
Federal Driving Cycle based on
advanced combustor data.
Original 1976 Federal standards
-8-
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development of an improved version of its sixth-generation engine for
powering an intermediate-size car. Engine design for a compact car
•will be examined in a recent extension to this program. The NASA
Lewis Research Center is playing an important role in this effort in the
areas of combustion, rotating machinery design and engine test. Fig-
ure 2 shows the EPA/Chrysler/NASA team.
5. While demonstrated fuel economy is low for gas turbine engine-powered
cars (about eight to nine miles per gallon for an intermediate-size car
over the Federal Emissions Test Driving Cycle), it is estimated that
by 1975 fuel economy for improved engines will rise to about 12 miles
per gallon and be competitive with that of full-size spark ignition engine-
powered cars. This improvement is expected to result from a variety
of effects as noted in Table 2.
6. In the future, if ceramic turbines are developed, a further substantial
rise in turbine operating temperature appears possible, leading to a
significant reduction in fuel consumption. For example, it is estimated
that a temperature increase at the turbine inlet from a current value
of about 1800°F to a future value of 2500° F would result in about a
20 percent improvement in fuel consumption. An additional benefit from
the use of ceramics might be reduced manufacturing cost.
Rankine Cycle Engines
1. Under the AAPS Program, the Rankine cycle engine is in an advanced
state of development, having progressed to the point where several
complete engine systems have been tested on engine dynamometers.
Some of these engine systems are water-base working fluid designs
(steam engine) that present the problem of fluid freezing at low tem-
peratures. Others rely on an organic-type working fluid as one means
of circumventing this problem. The Rankine cycle contractors who
have worked on various aspects of the AAPS Program appear in
Figure 3.
2. Preliminary analyses of steady-state emission data from the AAPS
Program show that the emissions from this type of engine should meet
the original 1976 Federal emission standards and that fuel economy can
be competitive with current emission-controlled spark ignition engines.
A breakthrough in the design of the engine condenser has resulted in
much smaller units than in the past and this development has consider-
ably facilitated engine installation into current automobile engine
compartments.
3. The task of repeated demonstrations of low emissions in transient
operation (including cold start) with a fully automatic control system
has been initiated under the AAPS Program. Scientific Energy Systems
Corporation has been selected from several competing contractors to
provide EPA with a vehicle-installed steam engine system for testing
-9-
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o
I
AAPS
BRAYTON POWER SYSTEMS DEVELOPMENT TEAM
1
[NASA LEWIS TECHNOLOGY PROGRAMS
i
COMBUSTOR HEAT EXCHANGER MANUFACTURING
(low cost|
-CATALYTIC [-OWENS ILLINOIS h-AIRESEARCH
linhouse) ^-CORNING I-PRATT & WHITNEY
-SOLAR
-GENERAL ELECTRIC
-AEROJET LIQUID
ROCKET CO.
i
[ EPA
r~
COMBUSTOR
I- WILLIAMS RESEARCH
-SOLAR
-AIRESEARCH
-PRATT & WHITNEY
-MECHANICAL
TECHNOLOGY, INC.
-NORTHERN RESEARCH
-GENERAL ELECTRIC
LAEROJET LIQUID
ROCKET CO.
SYSTEM IMPROVEMENT
T
TECHNOLOGY PROGRAMS |
1 I 1
HEAT EXCHANGER MANUFACTURING STUDIES
(low cost]
-OWENS ILLINOIS (-AIRESEARCH
-CORNING "-PRATT & WHITNEY
1 1
ECONOMIC ADVANCED TURBINE
I-WILLIAMS DESIGN
RESEARCH [-GENERAL ELECTRIC
I-AIRESEARCH
LpRATT & WHITNEY
| NASA
1
SYSTEM
IMPROVEMENT
COMPONENT
TESTING
POWER SYSTEM
TESTING
1
LEWIS J
1
AERODYNAMIC
IMPROVEMENT
j- TURBINE
I- COMPRESSOR
LFLOW PASSAGES
1
| CHRYSLER |
SYSTEM COMPONENT
IMPROVEMENT IMPROVEMENT
-COMPONENT
TESTING
-POWER SYSTEM
TESTING
-VEHICLE
TESTING
-CONTROLS
-HEAT EXCHANGER
-TRANSMISSION
-INHOUSE COMBUSTOR
-GOVERNMENT FURNISHED
EQUIPMENT (from NASA
Technology Programs)
-NOZZLE ACTUATOR
-FREE ROTOR
1
GAS TURBINE
UPGRADING
Figure 2. EPA/AAPS Brayton Power Systems Development Team
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Table 2. Fuel Economy Improvement Items for Baseline Gas
Turbine Development Program
Imp r o vement
Item
Water Injection
(Upstream of Compressor)
Variable Inlet Guide
Vanes
Ceramic Regenerator
Higher Cycle
Temperature
Recovery and Reduction
of Heat Loss
Power Turbine
Compressor Turbine
Compressor
Improvement
Description
Reduced engine size
for same horsepower
Reduced engine size
for same horsepower
Better effectiveness
Reduced engine size
for same horsepower
Reduced parasitic
losses
Higher efficiency
Higher efficiency
Higher efficiency
Imp ro vement
Goal
10% hp
12% hp
+4%
7%hp
50%
+ 2 - 4%
+4%
+ 1%
Estimated
Improvement
in Tank Mileage
5%
6 to 8%
6%
5%
6 to 10%
7%
8%
2%
hp = horsepower
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ENVIRONMENTAL PROTECTION
AGENCY
1
1 1 1
CONTRACT TECHNICAL R&D
MONITORING SUPPORT PROGRAMS
SYSTEM CO
1
(LOGY PROGRAMS |
|j:OMBUSTOR | | CONDENSER |
\ITR
-SOLAR
GEO SCIENCE
LTD
GARRETT
" AIRESEARCH
-UNIV. OF MICK
r~
i
i
MODELING
STUDIES
L GENERAL
ELECTRIC
IIGAN
1
-HAAvt |LUBRICATION| | FLUIDS) [FEEDPUMP
-BATTELLE 1 1
L ELECT^C LMONSAN™
ACTORS
-LEAF
- CHAI
1
EVANS
i
I
I
1
| WATER-TURBINE] | WATER-RECIPROCATOR | [ORGANIC WITH RECIPROCATOR | [ ORGANIC WITH TURBINE |
I
I
1
| LEAR MOTORS | |STEAM ENGINE SYSTEMS*| [THERMO ELECTRON CORP]
1
T
GENERAL MOTORS
-RICARDO
NCHRYSLER
-ESSO
-BENDIX
L
FORD
| AEROJET
LGENERAL
MOTORS
*(now Scientific Energy Systems Corp)
Figure 3. EPA/AAPS Rankine System Development Team
-------
(Figure 4). This engine design utilizes a reciprocating piston expander
for transmitting power through a transmission to the rear wheels (in
contrast to competing designs based on a turbine expander).
4. Future AAPS program efforts are expected to concentrate on achieving
improvements in fuel economy and investigating low-cost production
techniques.
5. In addition to the EPA AAPS Program, the U.S. Department of Trans-
portation has investigated Rankine cycle power systems for buses, and
the State of California, under the Clean Car Project, has been testing
this type of engine for passenger car use. Other domestic and foreign
programs are being funded by private capital.
Stirling Cycle Engines
1. Stirling cycle engines have the potential for demonstrating excellent fuel
economy, multifuel capability, very low noise and vibration, and emis-
sions low enough to meet the original 1976 Federal emission standards.
2. The most significant advancement in recent times is a major reduction
in engine volume, coupled with an increase in power output per pound
of engine weight. This has led to the initiation of a Ford demonstration
program that involves the installation of engines in Torino and Pinto
automobiles. N. V. Philips Laboratories at Eindhoven, Holland, will
furnish the engine for the Torino installation (Figure 5), and United
Stirling of Sweden will provide the Pinto engine.
3. A summary of emissions and fuel economy projections made by Ford
for the Stirling engine appears in Tables 3 and 4. Primary problem
areas requiring further development work for resolution are:
a. For efficient operation of this engine, the radiator in certain
designs can be about two and one-half times as large as that for
a comparable internal combustion engine. A reduction in radiator
size will be necessary to permit satisfactory installation in cur-
rent automobile engine compartments.
b. In order to contain the high-pressure hydrogen working fluid,
the array of heater tubes is now made of nickel-chrome alloys.
These tubes are expensive to fabricate and, therefore, produc-
tion processes must be improved or new designs must evolve to
aid in reducing engine manufacturing costs.
4. Other problems with the Stirling engine include the low life of piston
seals, hydrogen diffusion through the cylinder walls and seals, and the
need for low-cost power control capable of providing smooth power
transitions. Engineering solutions appear available, but they require
further development and demonstration.
-13-
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Figure 4. 1 50-Horsepo\ver Steam Engine (Scientific Energy Systems Corporation)
-------
REGENERATOR
COOLER
TUBES
WATER
INLET
IGNITOR
ATOMIZER
DOUBLE-ACTING
PISTON
OIL
PUMP
WATER
OUTLET
OUTPUT
SHAFT
SWASH
PLATE
GUIDE PISTON
AND SLIDERS
ROLL SOCK
PISTON ROD
BURNER
ROTARY'
PREHEATER
HEATER
TUBES
Figure 5. Philips Stirling Engine with Swash-Plate Drive
-------
Table 3. Stirling and Spark Ignition Engine Fuel
Economy Comparisons
Driving Cycle
Consumer Average
Suburban Driving
City Traffic
Superhighway
Fuel Economy, mi/gal
1976 Ford V8
10.7
13.3
8.2
13. 0
Stirling -Torino
(Projected)
14.7
17.9
11.4
16. 6
Gain,
%
37
35
39
28
mi/gal = miles per gallon of gasoline
Table 4. Constant Volume Sampling Test
Simulation Emissions
Comparison
Philips Engine
Original 1976 Federal Standard
Emissions, gm/mi
HC CO NO
X
0.10 0.31 0.175
0.41 3.40 0.4
gm/mi = grams per mile
-16-
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Diesel Engines
1. A number of manufacturers (including Mercedes, Peugeot and Opel)
are currently marketing a passenger car powered by a Diesel engine.
2. Based on test data taken by EPA, research institutions, and engineering/
manufacturing firms, light-duty vehicles powered by Diesel engines
have shown emissions below the original 1975 Federal emission stan-
dards, but there are no indications as yet that this engine can adequately
meet the original 1976 Federal oxides of nitrogen standard. Addition-
ally, Diesel odor and particulates (smoke) have long been recognized as
undesirable exhaust emission products. Progress toward determination
of the cause of the odor has been very slow, though its control has been
achieved in some engines through fuel injection system refinements.
3. The fuel economy of Diesel-powered vehicles over the Federal Emis-
sions Test Driving Cycle is between 50 and 70 percent better than
that achieved by the average 1973 model year emission certification
vehicles tested at the same inertia weight. Currently, however, be-
cause installed Diesel engine power is relatively low, vehicle accelera-
tion is significantly lower than that found with spark ignition engine-
powered cars. On an equivalent performance basis, the fuel economy
advantage of a higher powered Diesel vehicle would be expected to be
smaller than that for current lower powered Diesel vehicles.
4. The power output per pound of engine weight of currently produced light-
duty Diesel engines is considerably lower than that presently offered in
spark ignition engine-powered domestic automobiles. Methods for in-
creasing the power output per pound of engine weight include: (a) the
increase of power by turbocharging or supercharging, and (b) the de-
crease of engine weight and bulk by a reduction in engine compression
ratio and a shortened design life. At the present time, there does not
appear to be any development work on any of these approaches.
Wankel (and Other Rotary Piston Engines)
1. Although production levels of rotary engine-powered cars have been
rising, they represent a very small fraction of the automobile popula-
tion. Currently, these engines appear principally in Mazda vehicles
manufactured by Toyo Kogyo. Production levels are expected to in-
crease with the limited introduction scheduled for the 1975 model year
of the Chevrolet Vega powered by the General Motors rotary engine.
2. For a given power rating, the rotary engine is lighter and smaller than
a reciprocating piston, spark ignition engine. Reductions in engine
size and weight can also lead to smaller and lighter vehicles as the re-
sult of more compact packaging.
-17-
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3. A manufacturing problem exists in attempts to increase production
rates. Because of complex machining operations required on both the
housing and rotor, production of this engine is currently limited to
about 25 per hour per line (compared to piston engine rates of over
100 per hour per line). This limitation appears to have a significant
impact on manufacturing costs.
4. Technological problems still exist for some engine designs. These
consist of high gas seal leakage, high thermal stresses, poor low-
speed fuel economy, and high exhaust emissions without aftertreatment.
With aftertreatment (a thermal reactor), the Mazda rotary engine has
demonstrated the ability to meet the original 1975 Federal emission
standards.
Stratified Charge Engines
1. Honda has a divided-chamber version (designated CVCC) (Figure 6) of
the stratified charge engine in production. Without incorporation of
additional emission control systems, its CVCC engine-powered Civic
vehicle met the original 1976 Federal emission standards for hydrocar-
bons and carbon monoxide, while oxides of nitrogen -were about twice
the standard. Vega and Impala vehicles achieved similar emission
levels at low mileage when powered by General Motors engines modi-
fied by Honda to the CVCC configuration.
2. Army M-151 (jeep) vehicles equipped with the Texaco (TCCS) (Figure 7)
and the Ford experimental open-chamber version of the stratified charge
engine have met the original 1976 Federal standards with the use of an
emission control system incorporating oxidation catalysts and exhaust
gas recirculation. But these vehicles were unable to negotiate the high
acceleration modes of the Federal Emissions Test Driving Cycle.
3. Fuel economy of the Honda Civic vehicle with the CVCC engine, as
measured over the Federal Emissions Test Driving Cycle, was about
ten percent lower than that of conventional Civic vehicles and 16 per-
cent lower than that of equivalent-weight 1973 model year emission
certification vehicles. A Vega vehicle with this type of engine showed
fuel economy five to ten percent better than that of the standard Vega.
A CVCC-powered Impala and a Texaco TCCS-powered M-151 vehicle
showed equal or slightly better fuel economy compared to the respective
unmodified vehicles.
4. Both open-chamber and divided-chamber engines have demonstrated a
lo\ver sensitivity to fuel octane number than the basic spark ignition
engine.
5. A potential problem area for both open-chamber and divided-chamber
engines is high production cost. The open-chamber engine also re-
quires cylinder fuel injection. Additional potential problem areas
18-
-------
Figure 6. Honda CVCC, Divided-
Chamber Stratified
Charge Engine
Figure 70 Texaco Cup Combustion, Open-
Chamber Stratified Charge
Engine
-------
related to open-chamber engines include emission control system
durability and the current inability to achieve oxides of nitrogen emis-
sion levels that meet original 1976 Federal emission standards without
incurring a substantial loss in fuel economy.
COMPARATIVE REVIEW OF ALTERNATIVE ENGINES
Each of the heat engines and powerplants being considered as
an alternative to the spark ignition engine for automobile propulsion has its
own unique characteristics. If sufficient performance data were available,
the engines could be compared readily and objectively to provide a relative
ranking of these characteristics. In general, such data are limited in scope
or not available for this purpose because the engines are in an early and dif-
ferent phase of development where more effort has been devoted to establishing
proof of principle for a particular design concept rather than to establishing
all of the prototype baseline performance characteristics. Therefore, com-
parisons are at best subjective.
Of overriding importance, however, is that each alternative
engine offers the potential of meeting the original 1976 Federal emission
standards, and most show reasonable progress towards these standards as
shown by the representative data for selected engines in Table 5. It should
be stressed that because the engines are at different stages of technological
development, it is not meaningful to attempt to compare and rank them with
regard to the potential for achieving the lowest possible emissions, whether
for a single exhaust emission specie (e.g., hydrocarbons) or all three species.
Besides emissions, other topics of concern in selecting an
engine to supplant the spark ignition engine are adaptability to mass produc-
tion, purchase and maintenance costs (including durability factors), fuel con-
sumption, fuel compatibility, weight and size impact on vehicle packaging re-
quirements, flexibility and responsiveness to driver commands, noise, etc.
Current development efforts are directed toward engine size and weight
reductions that will permit engine installation in conventional automobile
engine compartments. Additional effort is also being applied to ensure engine
flexibility and responsiveness and to reduce noise levels.
-20-
-------
Table 5. Selected Exhaust Emission Data, Alternative Engines
Engine
Gas Turbine
Chrysler engine
Solar advanced
combustor
General Motors
Z 25 -horsepower
Rankine Cycle
Water Reciprocating
Stirling
Diesel
Mercedes Benz 220D
Wankel
Toyo Kogyo
Stratified Charge
Honda CVCC
Ford M-151 PROCO
Exhaust Emissions, a
gm/mi
HC
-0.26
0. 11
0.02
0.09
0. 10
0.34
0.35
0.24
0.37
CO
3.99
3.34
2.4
0.5
0.31
1.42
2.2
1.75
0.93
NOX
2. 21
0.34
0.32
0.2
0. 18
1.43
0.49
0.65
0.33
Remarks
Background level subtracted
from measured values
Calculated, based on
combustor tests
Chassis dynamometer
tests, experimental engine
Calculated, based on
component tests
(1972 FTP)
Calculated, based on
component tests
EGR and engine modifi-
cations required to
reduce NO emissions
X
Low-mileage tests with
thermal reactor and EGR
Average values for 50, 000-
mile test car (Civic)
Based on EPA tests with
catalyst and EGR
a!975 Federal Test Procedure (FTP) EGR = Exhaust gas recirculation.
except where noted (grams per mile).
-------
Mass production and the resulting purchase cost are factors
that have been reviewed in screening the various alternative engines, but
firm quantitative comparisons are generally not available.
This report is intended to depict the status of development of
complete alternative engine systems. But it is extremely difficult to provide
this information on an absolute basis because one member of the automotive
industry is more advanced with respect to one engine type than others. Also,
groups outside of the industry appear to be conducting more advanced work
than those in the industry (e.g. , on at least one type of alternative heat engine/
electric hybrid) and an overseas firm is producing rotary engines while no
company in the U. S. has produced any as yet. Perhaps the most informative
means for illustrating this status is one which relies on subjective judgments
and qualitatively relates the investment costs to knowledge generated about
each alternative system throughout all phases of product development. Fig-
ure 8 shows this type of relationship for the alternative heat engines and
electric and hybrid systems and shows where the conventional engine may be
placed on this curve. In effect there is not a single such curve wherein each
alternative system moves as development costs increase. Use of a single
curve simply facilitates the comparisons.
The figure was formulated by the staff of the AAPS Division and
is intended to show the relative state of development and which particular
phase of development each system is in as of the end of 1973 in the U.S. The
figure applies to passenger car systems.
Several conclusions can be obtained from this figure. These
include:
• It takes a considerable investment of funds (and time) to
gain the knowledge of each type of system that manage-
ment needs to make a decision on committing a given
system to production (note that the abscissa has a loga-
rithmic scale).
• In the very early phases of development much knowledge
can be obtained with the use of relatively small funds.
-22-
-------
00
I
GO/NO-GO DECISION
ON MASS
PRODUCTION
ADVANCED ROTARY
STRATIFIED CHARGE (TCCS & PROCO)
STRATIFIED CHARGE (CVCC)
AND ROTARY (Wankel)
INTERNAL COMBUSTION ENGINE
(spark ignition and conventional dieselj
.-ELECTRIC (high temperature)
ENGINEERING
DEVELOPMENT
PRODUCT IMPROVEMENT
EXPLORATORY
DEVELOPMENT
L
ADVANCED
DEVELOPMENT
INVESTMENT COST-
(Logarithmic Scale)
Figure 8. Knowledge Made Available as a Function of
Investment in Engine Development
-------
• As a system proceeds into later development phases,
investment cost increases at rates considerably in
excess of the gain in knowledge of the system.
• There is no single alternative engine that comes close
to the internal combustion engine in terms of knowledge
of the system. This is because the past investments in
this type of engine are far greater than investments in
any alternative.
With respect to fuel consumption, the data are sufficient for
an illustrative comparison among various engines. Figure 9 presents mea-
sured fuel economy results for the spark ignition engine contrasted with
(NOX -0.4 gm/mi)
0 MEASURED ENGINE IN VEHICLE
O MEASURED ENGINE IN VEHICLE (NOX - 2.0 gm/ml)
A PROJECTED BASED ON ENGINE COMPONENT MEASURED
25
_
8.
E15
10
3 5
LL.
PERFORMANCE (NOX - 0.4 gm/mi)
PROJECTED DATA MODIFIED FOR POWER TO WEIGHT RATIO
OF SPARK IGNITION ENGINE POWERED CARS
gm/mi = grams per mile
TEXACO
. STRATIFIED
^ CHARGE o /22Q_D
& FORD D
PROCO
(Jeep)
GAS
TURBINE STIRLING
(1976) A
= grams per
°^ DIESEL-
MERCEDES
CARTER
STEAM
RANKINE
O
HONDA
CVCC
TEXACO
STRATIFIED
CHARGE
(jeep)
WANKEL
MAZDA
WILLIAMS O
RESEARCH
GAS TURBINE
SPARK
GAS
TURBINE
(1975)
IGNITION
AVG 1957-1967 CARS
(NOX-6.0 gnVmi)
I _ I I
AVG 1973 CARS _\
(NOX~3.1 gm/mi)
I
2000 25000 3000 3500 4000 4500
INERTIA WEIGHT, pounds
5000 5500
Figure 9. Fuel Economy Over the Federal
Emissions Test Driving Cycle
(Equivalent Gasoline Fuel)
-24-
-------
measurements and estimates of fuel economy for alternative engines. As can
be seen, some alternative engines appear capable of delivering superior fuel
economy, particularly when judged against the degraded fuel economy of ex-
haust emission-controlled 1973 model year cars. Even on this basis an
absolute comparison is difficult because the fuel economies of the internal
combustion engines change with model year.
-25-
-------
ALTERNATIVE NONPETROLEUM-BASED
AUTOMOTIVE FUELS
Domestic liquid petroleum products satisfied 74 percent of
the United States energy consumption in 1971; they are expected to satisfy
only about one-half of the needs in 1985 and less than one-half in 2000. This
excess demand-versus-supply situation provides a strong motivation for gov-
ernment agencies and the transportation industry (which consumes at present
about 55 percent of liquid petroleum products) to investigate the potential of
alternative nonpetroleum-based fuels for automotive applications. Several
alternative fuels were considered as replacements for, or partial supple-
ments to, conventional petroleum-based fuels. These were evaluated on the
basis of availability, compatibility with existing distribution and storage sys-
tems (both mobile and stationary), suitability for use with personal passen-
ger cars, relative advantages in terms of vehicle fuel economy and emissions,
costs to the consumer, capital investment costs, critical research gaps, tech-
nological status, and the time scale for production implementation. A prin-
cipal data source used -was two AAPS-funded studies (with the Institute of Gas
Technology and Exxon Research and Engineering Company) concerned with
the assessment of alternative automobile fuels.
In evaluating the potential of alternative fuels for transporta-
tion, the energy source from which they are derived is a prime considera-
tion. Sources available in the future will be coal, oil shale, tar sands,
nuclear energy, and solar energy, while liquid petroleum and natural gas
will be in continued short supply. Significant production of liquid petroleum
fuels from coal, oil shale, and tar sands cannot be expected until the far-
term (1985-2000) period. Contributions to domestic energy needs from
nuclear and solar energy are not expected until even later periods.
1 Exxon and IGT designations were: near term (1975-1985), mid-term
(1985-2000), and far term (beyond 2000).
-27-
-------
Coal is relatively plentiful in the United States, but its
availability will be limited by the mining rate. Oil shale resources are not
as plentiful and domestic tar sands represent substantially lower fuel re-
sources than oil shale.
According to estimates of the National Petroleum Council and
other sources, the domestic energy resource base for these fuels is
80,200 X 1015 British thermal units (3.21 X 1012 tons) for coal, 9549 X 1015
British thermal units (1781 X 109 barrels) for oil shale, and 127 X 1015 Brit-
IS
ish thermal units (23.5 X 10 barrels) for tar sands. For coal resources,
39, 000 X 10 British thermal units are proven and 41, 200 X 10 British
thermal units are reasonably assured. For oil shale resources, 116 X 10
British thermal units are proven, 1517 X 10 British thermal units are
reasonably assured, and 7916 X 10 British thermal units are speculative.
The tar sands figure is designated as a reasonably assured resource. Re-
coverable reserves are less than the figures cited and depend largely on
extraction economics, extraction procedures, and possible legal restraints.
Nuclear energy, if developed at the rate forecast, could in-
directly benefit the transportation sector by partially relieving the electric
sector from the use of fossil fuels. These benefits to the electric sector
could also be supplied by solar energy, but this would require a major tech-
nology breakthrough to be of advantage to the transportation sector. Thus,
solar energy cannot be considered for the near-term period (1975-1985) and
may be problematical for use to the year 2000.
The evaluation of each fuel was predicated on numerous inter-
acting factors, among which were abundance of domestic resources, techno-
logical status of production techniques, schedule for mass production, esti-
mated capital and consumer costs, and adaptability to both internal and ex-
ternal combustion types of engines for automobiles (including characteristics
related to fuel economy, exhaust emissions, handling, storage, and toxicity).
Table 6 lists the candidate fuels and summarizes their availability and suit-
ability as future alternatives to petroleum-based gasoline and distillate fuels.
-28-
-------
Table 6. Summary of Availability and Suitability of Alternative
Nonpetroleum-Based Automotive Fuels
CO
vO
I
Fuels
Synthetic gas-
oline and dis-
tillate
hydrocarbon
Methanol,
Ethanol
Methane
(CNG or LNG)
Propane,
Butane (LPG)
Hydrogen
Ammonia,
Hydrazine
Reformed
fuels
Present Energy
Source
Liquid
petroleum
Natural gas,
liquid hydro-
carbons
Natural gas
Natural gas,
liquid hydro-
carbons
Petroleum,
gas, coal,
water (by
electrolysis)
Same as
hydrogen
Liquid hydro-
carbons
Future Energy
Source
Coal, oil
shale
Coal, possibly
solid waste
Coal, possibly
solid waste
Coal
Coal, nuclear
(electrolysis)
Same as
hydrogen
Coal, oil
shale
Fuel Available
in Limited
Quantity
(Near-Term
Energy Source)
Pre-1985
Pre-1985
Pre-1985
Pre-1985
Post-1985
Post-1985
Post-1985
Fuel Available
in Significant
Quantity
(Future Energy
Source)
Post-1985
Post-1985
Post-1985
Post-1985
Post-2000
Post-2000
Post-1985
Future
Suitability for
Automotive
Use
Excellent
Good,
Fair
Fair
Fair
Fair to
poor
Poor
Fair
Research Gaps
in Engine
Application
More engine
data
More engine
data
More engine
data. Resolve
storability
problem
More engine
data
More engine
data. Resolve
storability
problem
Not worth
pursuing
More engine
data. Devel-
opment of fuel
reforming
Factors
Inhibiting
Fuel Use
Major factors
identified
Cost, per-
formance,
compatability
factors
On-board
storage, dis-
tribution
network
More expen-
sive than
synthetic
gasoline and
similar fuels
On-board
storage, dis-
tribution
network, safety
Toxicity,
safety, cost
Cost and
complexity
Possible application when mixed with CNG = compressed natural gas
gasoline (methanol blend). LNG = liquid natural gas
LPG = liquid petroleum gas
-------
Additional information is provided in Table 7 which also lists estimated fuel
costs (ex tax) at the pump. It is noted that evaluations of the ability of
nonpetroleum-based alternative fuels to compete in price with petroleum-
based fuels are in a state of flux because of the recent fluctuations in the
cost of automotive fuel. Likewise, cost estimates for alternative fuels may
be revised as more data are acquired from future pilot and prototype demon-
stration fuel production plants.
It should also be recognized at the outset that an important
factor affecting the rate of possible implementation of each of these fuels
(except synthetic gasoline and distillate fuels) would be the need for a com-
pletely new nationwide specialized distribution and storage network. Un-
doubtedly, a dual-fuel system would be required for an extended period of
time to satisfy the needs of both gasoline-fueled vehicles and new vehicles
designed to use the alternative fuels.
Based on all the aforementioned considerations, it would
appear that synthetic gasoline and distillate hydrocarbons manufactured from
coal and shale offer the greatest promise for contributing to automotive fuel
requirements in both the near-term and far-term periods. Coal-derived
methanol, particularly in a methanol-gasoline blend, could be considered a
secondary fuel source if certain technical problems were solved. Another
alternative fuel of merit is hydrogen, but it can only be considered as a
possible contributor to automotive needs in the period beyond the year 2000.
The rationale for these selections is amplified in the following highlights
which present the essential elements of the current status of alternative
automotive fuels.
Synthetic Gasoline and Distillate Hydrocarbon Fuels
1. Synthetic gasoline and distillate hydrocarbon fuels could be manufac-
tured from coal, oil shale, tar sands, or organic waste products.
They possess the primary advantage of expected complete compati-
bility with existing and advanced automotive powerplants, as well as
with distribution facilities down to the local gas station.
-30-
-------
Table 7. Logistic Factors for Use of Alternative Nonpetroleum-Based
Automotive Fuels
Fuel
Gasolineb
Distillateb
Liquid
Hydrogen
Ammonia
Hydrazine
Methanol
EthanoL
Methane
Propane
Est. Cost at Pump in 1973
Dollars (Taxes Excluded)
$/!06 Btu*
3. 15 (from coal)
2.60 (from shale)
2. 50 (from coal)
2. 00 (from shale)
7. 00 (from nuclear electrolysis)
4. 70 (from coal)
7. 65 (using hydrogen from
electrolysis)
Over 20
3.40 (from coal)
7. 80 (from organic waste)
3.80
Greater than 3. 80 (from coal
liquefaction)
a$/10 Btu - Dollars per million British therma
Fuels for Automotive Transportation (in three
Vehicle
Storage
Excellent
Excellent
Poor
Fair
Good
Good
Good
Poor
Fair
Toxicity
Medium
Low
Low
High
High
Medium
Low
Low
Low
Safety
High fire hazard
Low fire hazard
High fire and
explosion hazard
Moderate fire
hazard
High fire and
explosion hazard
Moderate fire
hazard
Moderate fire
hazard
High fire and
explosion hazard
Moderate fire
hazard
C ompatability
with Petro-
leum Fuels
High
Low
Low
Low
High if water
controlled
High if -water
contamination
controlled
Low
Low
1 units for the post- 1985 period. Data are primarily from F. H. I
volumes), EPA-460/3-74-009-4-a, Exxon Research and Engineeri
Status of Distribution to Consumer
Existing
Existing
Major development and investment required
Some experience in farm distribution. Major
expansion required with emphasis on safety
Major modifications to existing gasoline system
in areas of materials compatibility and safety
Existing gasoline system could be used with
and corrosion
Same as Methanol
About the same problem as for Hydrogen
Limited availability at present.
Requires extension
-------
2. Coal (particularly from strip mining processes) is by far the largest
and most probable domestic energy resource available for synthetic
fuel production, followed by oil shale. Additional domestic sources
of much less potential, in terms of ability to meet projected energy
needs, are tar sands and organic waste products.
3. The production cost in the post-1985 period for gasoline and distillate
hydrocarbon fuels derived from oil shale is estimated to be competi-
tive with current costs of conventional petroleum-based sources.
Equivalent liquid hydrocarbon fuels derived from coal are more ex-
pensive but are also competitive. In either case, waste product
disposal constitutes a serious environmental problem, with processed
oil shale being the most critical concern.
4. The production economics for liquid hydrocarbon fuels derived from
coal and shale will ultimately depend on (a) the efficient commerciali-
zation of various production processes currently under evaluation in
laboratory and pilot-plant models, and (b) the transport distance re-
quired for raw and/or refined products. Intensive capital investment
will be required if several 50,000- to 100, 000-barrel-per-day plants
are to be in operation in the 1980-1985 period.
5. Little information is available on the actual use of synthetic gasoline
or distillates in automotive engines. A test program to verify the
compatibility of these fuels with automotive engines is planned for
Fiscal Year 1975 under an interagency agreement between EPA and
the Bureau of Mines.
Methanol and Methanol-Gasoline Blends
1. Pure methanol has seen limited successful use with spark ignition
engines powering automobiles. It offers the following advantages:
a. An increase in power from existing engines fueled with gaso-
line, largely because methanol heat of vaporization character-
istics lead to increases in air inducted into the engine and to
increases in net -work output.
b. An increase in efficiency and in power output per pound of engine
weight for new engine designs because the engine can operate at
higher compression ratios than with high octane premium
gasoline.
2. Certain disadvantages of pure methanol will require that careful prep-
aration by fuel distributors and automotive manufacturers precede its
-32-
-------
possible introduction into the retail sales market. Among these
disadvantages are:
a. Fuel economy (in miles per gallon) with pure methanol is about
half that with gasoline, necessitating a major increase in the
size of the automobile fuel tank and modifications to the car-
buretor fuel jets [although the energy expended each mile (in
British thermal units per mile) in powering an automobile with
methanol is equivalent to the energy expended with gasoline].
b. When contrasted with gasoline, vapor pressure characteristics
of pure methanol imply that there may be a greater incidence of
vapor lock with current automobile fuel system designs. Also,
cold start is more difficult and manifold preheating is required
to ensure complete vaporization in carbureted systems.
c. Miscibility between pure methanol and water can result in the
presence of water (from local atmospheric moisture) in the fuel
distribution system, in the service station tanks, and in the vehi-
cle tank, leading to possible corrosive action on metal surfaces in
piping, tankage, and within the engine itself. Corrosion inhibi-
tors may be required in the fuel to avoid this problem.
d. Synthetic methanol transport costs are expected to be higher than
those estimated for synthetic gasoline because, for equal energy
content, the pure methanol volume required to be piped, trucked,
and stored is approximately twice that of gasoline; therefore,
when distribution costs are included, the cost (ex tax) at the pump
to the consumer, per unit of fuel energy delivered, is estimated
to be 10 to 30 percent greater than that for synthetic gasoline from
coal and shale, respectively.
e. The solvent action of pure methanol may damage paint, metal,
and plastic surfaces; therefore, solvent-resistant materials
must be considered for use in all applications.
3. A greater near-term advantage may accrue from the use of methanol-
gasoline blends rather than pure methanol. This approach would con-
serve gasoline stocks to a small degree without necessitating major
redesign of automobiles or engines. It should be noted, however, that
even if methanol is added in a methanol-gasoline blend only to the five
percent level, current automotive fuel consumption would require
about five times the present U.S. methanol production.
4. As with pure methanol, methanol-gasoline blends have a higher octane
rating than gasoline alone. But there are indications that the motor
octane number (MON) increase is not nearly as great as that which
-33-
-------
would be expected from measured increases in the research octane
number (RON). This would indicate that engine road performance
increases will not be as marked as those found in the laboratory.
5. Vapor lock and water miscibility problems would be present to a much
greater degree with methanol-gasoline blends than with pure methanol.
An example of these problems is the separation of gasoline and metha-
nol in the presence of very small amounts of water, particularly at low
temperatures. Solutions to these problems may be possible, but they
require laboratory and road test verification.
6, The majority of published data on the application of methanol and
methanol-gasoline blends to fueling automotive engines is about 20 to
30 years old. The use of new materials, engines, gasoline blends,
and lubricating oils is a compelling factor for acquiring more con-
temporary characteristics of methanol in order to verify or invalidate
older concepts regarding advantages and disadvantages of this alter-
native fuel. In this regard, the adaptability of methanol and methanol-
gasoline blends to modern automotive systems will be explored sys-
tematically in a test program initiated by the Bureau of Mines through
an interagency agreement with EPA. Other research programs in-
vestigating methanol and methanol blends are in progress, or planned,
at several universities and industry research laboratories.
Methane (Synthetic Natural Gas )
1. Because of supply constraints of natural gas, efforts are under way to
develop the technology for deriving synthetic natural gas from either
coal or liquid hydrocarbons. Production levels will depend on the com-
pletion of coal gasification plants which are first expected to be in oper-
ation in the post-1980 period.
2. Liquefied gas (natural or synthetic) is more attractive than the gaseous
form because of its greatly increased density (resulting in reduced
storage volume requirements in the vehicle). However, the low boil-
ing point requires application of cryogenic tank insulation techniques
which add substantially to automobile tankage weight and cost relative
to a conventional gasoline system.
3. Energy expenditure per mile in powering an automobile with an engine
converted to operate on natural gas is approximately equal to or better
than that for a similar vehicle using a modern gasoline engine equipped
with emission control devices. In general, exhaust emissions with
natural gas are expected to be lower than those with gasoline.
Also referred to as "substitute natural gas."
-34-
-------
4. A significant factor in the use of natural gas in place of gasoline as an
automotive fuel is the reduced activity of hydrocarbon emissions in the
formation of photochemical smog. Total hydrocarbon activity is four
to six times less than that of gasoline.
5. Because of the difficulties in implementation of an adequate fuel dis-
tribution system throughout national urban areas, and because of the
problems of storage on the vehicle, neither liquified nor compressed
natural gas is considered to be a primary alternative fuel candidate
for large-scale automotive use. Usage would be expected primarily
for commercial fleet operations. However, synthetic natural gas may
be expected to be of significance in replacing petroleum fuels for sta-
tionary electric generating power plants based on projections that, in
the far-term period, 20 to 25 percent of the total gas supply may come
from coal gasification.
Propane
1. Propane appears suitable for use in all of the alternative engines cur-
rently being considered. Vehicle tankage volume and weight is less
than that required for methane, and cryogenic cooling is not required
for storage in a liquid form if the fuel is pressurized to about 250
pounds per square inch. However, as in the case of methane, this fuel
is not considered a primary alternative candidate for large-scale auto-
motive use because of distribution and storage problems.
2. Exhaust emissions from propane show marked reductions when com-
pared to those from gasoline, but fuel economy trends are inconsistent
amongst different data sources.
3. Adequate availability of the fuel is a major problem because the major
production source of propane is natural gas processing plants (a de-
clining resource). Hence, a new raw material source (e.g. , coal or
oil shale) and production process would be required to increase its
availability.
4. Consumer costs of liquid petroleum gas are generally similar to the
price of gasoline, as of mid-1973, but gasoline is cheaper for power-
ing an automobile on the basis of energy expended per mile. Further-
more, if in the future propane is manufactured synthetically from
coal, costs to the consumer are projected to be greater than for syn-
thetic methane (and certainly greater than for synthetic gasoline).
Ethanol and Ethanol-Gasoline Blends
1. Ethanol has been demonstrated to be compatible as a motor fuel with
present vehicles. In many parts of the world, it has been blended in
-35-
-------
concentrations varying between ten and 20 percent to alleviate
gasoline shortages. Pure ethanol or blends with gasoline have essen-
tially the same usage problems cited for methanol.
2. The economics and instability in the price of ethanol production based
on fermentation of agricultural raw materials and the poor fuel econ-
omy are additional major factors tending to limit its use. Ethanol -
gasoline blends have been considered, but the cheaper and equally
efficient methanol-gasoline blends are preferred.
Hydrogen
1. Success has been attained in carrying out the necessary mechanical
conversions to enable conventional gasoline engines to operate on
hydrogen. Indications are that extremely low exhaust emission levels
are possible. Fuel economy on an energy-expended-per-mile basis is
found to be comparable to that for gasoline, but maximum engine
power output for a given engine size is reduced significantly-
2. A major technical drawback with hydrogen as fuel for the automobile
is the problem of storage on the vehicle. Storage in compressed gas
form is not practical, and even in cryogenic liquid form storage is
complex and expensive, requiring a tank capacity three and one-half
times that needed for gasoline on an equivalent energy basis. Research
is under way to evaluate an alternative reduced-volume storage ap-
proach using metal hydrides; a means of also reducing the storage
weight will be necessary before this technique can be considered
practical.
3. Additional major obstacles to using hydrogen as a universal fuel con-
cern the energy supply adequacy for its manufacture as well as very
high costs to the consumer. Nuclear power will be a necessary fac-
tor in ensuring an adequate supply of energy for production of hydro-
gen by water electrolysis. On an equivalent energy basis, liquid
hydrogen cost to the consumer will be much greater than the cost of
gasoline or distillate derived from coal. Much of this cost is attrib-
utable to significant cost items connected with the liquefaction of
hydrogen and its subsequent transportation to, and storage at, retail
outlets.
4. Even if costs are reduced, hydrogen appears to be a possible fuel only
for the post-2000 period. The massive capital requirements for man-
ufacturing plants and distribution facilities, and the extensive period
needed for actual construction activities, preclude any earlier consid-
eration of this fuel as a major contributor to passenger car needs.
-36-
-------
Ammonia
i. The interest in ammonia as an engine fuel stems from the consideration
that it allows the storage of hydrogen in nitrogen hydride form at rela-
tively low pressures without some of the fire and explosion hazards as-
sociated with pure hydrogen. But the extreme toxicity of ammonia,
combined with expected high consumer costs, does not hold much prom-
ise for this fuel even for the far-term period.
Hydrazine
1. For the very same reasons cited for ammonia, hydrazine is considered
unsuitable as an alternative to petroleum-based fuels.
Fuels Reformed On the Vehicle
1. One approach -which is being investigated as a means of extending the
lean operating limits of gasoline engines in order to achieve low ex-
huast emissions is the incorporation of a fuel reformer device to
chemically convert all or a portion of the engine's fuel requirements
from gasoline (or any liquid hydrocarbon fuel) to a gaseous product
(principally hydrogen) prior to induction into the engine. Initial ex-
ploratory tests have indicated marked reductions in carbon monoxide
and oxides of nitrogen exhaust emissions at very lean air-fuel ratios,
but these positive factors are offset by high hydrocarbon exhaust
emissions. Fuel economy is projected by some investigators to be
equal to or better than that obtainable with a gasoline-powered engine.
2. Fuel-reformer concepts are still in the exploratory, proof-of-principle,
or feasibility determination stage. A number of critical data gaps must
be filled before the potential of reformed fuels can be fully assessed.
NASA has been funding the Jet Propulsion Laboratory to acquire data
and prove concept feasibility, and EPA is providing supplemental
funding for this work in addition to other contractor-supported pro-
grams for evaluation of similar concepts.
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ELECTRIC AND HYBRID POWER SYSTEMS
Electric and hybrid power systems are unique alternatives to
heat engines for automotive propulsion. The extensive use of electric vehi-
cles would shift the burden of controlling exhaust emissions from motor
vehicles to stationary electric generating plants supplying energy for re-
charging batteries. Furthermore, the current use of petroleum-based fuels
for automotive propulsion could be diminished and personal transportation
energy needs could be supported to a large degree by coal or nuclear
resources.
The basic powerplant in electric vehicle designs consists of
one or more electric motors and controllers, perhaps a transmission or
other gears, and a battery system. Lead-acid batteries have been used in
most cases, and the direct current electric brush motor is used by an over-
whelming majority of vehicle designers and fabricators. In some systems,
regenerative braking is used which causes the motor to operate as a gener-
ator, permitting recharging of the battery as the car decelerates. Figure 10
illustrates the main components of an electric car drivetrain in schematic
form.
Currently, a major problem is the limitation on the amount of
energy and power that can be delivered by a given-size battery; this limita-
tion has a direct effect on vehicle range and acceleration. Evidence of this
problem is seen in the restricted operation of contemporary electric vehicles.
Analytical studies have shown that battery requirements for powering a full-
performance family car are a specific energy density of about 135 watt-hours
per pound to satisfy vehicle range, and a specific power density of about
95 watts per pound to satisfy vehicle acceleration. Current battery capabili-
ties (Table 8) approach the power density requirement but fall far short of
the energy density requirement. With a compact electric car, travel dis-
tances comparable to those for a heat engine car (without refueling) cannot
be approached even with a battery system weighing about one-third of the
vehicle curb weight.
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DRIVE WHEEL^
o
I
ACCESSORIES
-1-
1 ELECTRICAL
POWER
SOURCE
CONTROLLER
ELECTRICAL
DRIVE EFFICIENCY
DRIVE WHEEL^
MECHANICAL
DRIVE EFFICIENCY
Figure 10. Main Components of an Electric Car Drivetrain
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Table 8. Characteristics of Currently Available
Secondary Batteries
Battery Type
Lead-acid
Nickel- iron
Nickel- cadmium
Specific
Energy
Density,
w-hr/lb
20
13
13
Energy
Density,
w-hr/in^
2.0
1.2
1. 1
Specific
Power
Density,
w/lb
100
60
80
Approx.
Relative
Cost
1
3
20
Remarks
Standard
Excellent life,
poor
maintenance
Good cycle life.
Cadmium sup-
ply limited
w-hr/lb = watt-hours per pound w/lb = watts per pound
w-hr/in^ = watt-hours per cubic inch
When promoting a new battery for development, with intended
application to electric vehicles, the technical comparison is most often based
on specific energy density. As electric vehicle programs proceed, other
factors, implicit in the design of battery systems, must be considered. One
objective of system design would be to reduce vehicle weight and to minimize
influences such as drag, frontal area, acceleration, and peak cruise speed,
which would allow a reduction in battery energy usage.
The problem of adequate operating range for electric vehicles
will remain until low-cost, high-capacity batteries become available. In the
interim, other concepts have been examined in the search for a low-pollution
vehicle that could satisfy personal transportation needs. One such concept
that has received the attention of automobile designers in the last five years
is the hybrid vehicle--a vehicle combining various power delivery systems
in the powertrain to use each form of power most effectively. The most
common form of system operation that has been studied for hybrid heat
engine/battery and hybrid heat engine /flywheel vehicles relies on the heat
-41-
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engine just to supply energy for vehicle cruise and for recharging the battery
or flywheel. The additional power needed for vehicle acceleration is supplied
by the battery or flywheel. With this form of heat engine operation, the
hybrid concept offers the possibility of reduced mobile emissions. A shift of
exhaust emissions and energy source to stationary electric generating plants,
as in the case of electric vehicles, would be possible only if the energy for
recharging the battery or flywheel was available from an external stationary
power source, and the heat engine was then used only for supplying emergency
power or for extending vehicle range on an infrequent basis.
Hybrid vehicle powertrain concepts can be grouped into two
broad classes (Figure 11). The first class, the series configuration, is
characterized by the principle that all the energy flowing from the heat en-
gine to the vehicle's rear wheels first passes through an intermediate energy
conversion device or devices. The second class, the parallel configuration,
is characterized by the principle that some of the energy flowing from the
heat engine passes directly to the rear wheels, with the balance routed in a
parallel path through an energy conversion device or devices.
A status review has been made of automotive electric and
hybrid power systems in this country and, where information was available,
in foreign nations. A number of prototype vehicles have been built with pri-
vate capital, and, in some cases, Federal funding has been used to evaluate
and test these systems. In particular, the results derived from EPA-
funded programs were reviewed within the context of the design goals estab-
lished for its AAPS Program for personal passenger cars. The following
highlights present the essential elements of this review. In addition to the
technical problems noted, estimated high manufacturing costs will likely be
a factor inhibiting the widespread application of these systems.
Generator, motor, and battery in the electric system, or flywheel and
transmission in the inertial system.
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HEAT ENGINE/BATTERY HYBRID
HEAT ENGINE/FLYWHEEL HYBRID
0)
UJ
SERI
CONFIGURATION
HEAT
ENGINE
MOTOR
WHEELS
TRANS-
MISSION
WHEELS
BATTERIES
HEAT ENGINE/BATTERY HYBRID
HEAT ENGINE/FLYWHEEL HYBRID
Z
PARALLE
CONFIGURAT
HEAT
ENGINE
1
r
GENERATOR
— *•
BATTERIES
^*"
GEARING
1
I
MOTOR
WHEELS
TRANSMISSION
Figure 11. Simplified Schematics, Heat Engine Hybrid Vehicle
Powertrain Concepts
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Electric Vehicles
1. In general, the majority of electric vehicles do not perform up to
heat engine vehicle capabilities--particularly with respect to maxi-
mum acceleration, speed, range, and hill-climbing ability, as well
as to passenger space and accommodations such as air conditioning
and heating. The usual maximum speed is 30 to 50 miles per hour;
and range is usually limited to 50 miles under conditions of optimum
cruise speed.
2. An additional problem with the electric vehicle is the power and time
needed for recharge of the batteries. Vehicle usage will be limited
unless provisions are made for exchange of depleted batteries for
fresh batteries. The capability of residential electrical grids to sup-
ply large power levels during daytime for a large number of electric
vehicles may be also a problem.
3. In selecting batteries for electric vehicles, a dominant parameter has
been purchase cost. Consideration must be also given to battery re-
placement costs and operating costs. For this reason, lead-acid bat-
teries are almost universally used.
4. No one battery has been developed yet to satisfy the combined design
requirements for low cost, long lifetime, high energy density (for
vehicle range), high power density (for vehicle acceleration), and
ease of maintenance.
5. For near-term applications, nickel-zinc batteries offer higher energy
density possibilities, but cost and nickel availability are drawbacks
for supplanting lead-acid batteries (nickel-cadmium batteries are even
more expensive). For far-term applications, the zinc-chlorine and
alkali-metal/high temperature battery systems, with significant in-
creases in energy and power density capabilities, appear promising if
development goals are achieved.
6. Work on batteries for electric vehicles is accelerating abroad. The
major activities are in the Federal Republic of Germany, Japan, the
United Kingdom, and the U.S.S.R. In each case, the government is
either formally participating in or is influencing the direction of the
work.
1. Excluding the special-purpose applications of golf carts, electric fork
lifts, and delivery vans, no major production of electric passenger
vehicles is expected for the next ten years. This picture could change,
should there be a major gasoline shortage, a restriction on operating
conventional vehicles in some areas due to air quality constraints, or
a breakthrough in battery technology which would allow much improved
vehicle performance and range.
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Hybrid Heat Engine/Battery and Hybrid Heat Engine/Flywheel Vehicles
1. The range limitations of electric vehicles are not found in the hybrid
heat engine vehicle concept. The hybrid vehicle under discussion uses
a small heat engine to provide road cruising power, with acceleration
power requirements provided by a battery in the case of an electric
energy storage hybrid, and by a flywheel in the case of an inertial
energy storage hybrid. By so restricting the operation of the heat
engine, early studies anticipated significant reductions in exhaust
emissions without the need for complex, costly exhaust treatment
devices, but results to date have not verified this expected
performance.
2. EPA contracted with several companies in the 1970- 1972 period to
perform evaluations of hybrid battery and flywheel systems. This
effort encompassed the analysis and test of hybrid systems as well
as associated components.
3 Elements of the TRW electromechanical transmission (heat engine/
battery hybrid) were assembled into a breadboard prototype unit and
tested as a complete integrated system. Powertrain efficiency -was
found to be below predicted values (though possibly correctable
through redesign), and exhaust emissions were reduced to or below
the level of the original 1976 Federal exhaust emission standards only
by the use of an exhaust emission control system consisting of ex-
haust gas recirculation, tricomponent catalysts, etc.
4. The Minicar, Inc. , hybrid heat engine/battery-powered car was defi-
cient in meeting performance goals, and exhaust emissions were not
reduced to acceptable levels.
5. Petro-Electric Motors has an operable hybrid heat engine/battery-
powered automobile which is undergoing test and evaluation at EPA
laboratories under the Federal Clean Car Incentive Program.
6. The Aerospace Corporation analytical study of hybrid heat engine/
battery-powered vehicles showed that, with a spark ignition engine,
exhaust emissions could meet the original 1976 Federal exhaust emis-
sion standards only by the use of aftertreatment devices in the exhaust,
along with engine modifications. In comparison to the conventional
automobile, no improvements in fuel economy were found. Similar
conclusions were arrived at by Lockheed in its analysis of a hybrid
heat engine/flywheel system.
7. The General Motors Stir-Lee I automobile (hybrid heat engine/battery)
achieved very good fuel economy, but proved to be very limited in
acceleration level and peak speed. Exhaust emissions (except for oxides
of nitrogen) were reduced, but not enough to meet original 1976 Federal
standards.
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8. Tyco concluded that a commercial state-of-the-art SLI (starting-
lighting-ignition) lead-acid battery was unsuited for hybrid vehicle
use because of life limitations, although required power levels were
achieved. Research tests with a revised design showed improvements
in meeting required EPA lifetime.
9. TRW/Gould also demonstrated that while a commercial state-of-the-
art SLI lead-acid battery approached required EPA design power levels,
it lacked the required lifetime. In a research battery design, TRW/
Gould achieved the required power density, but lifetime goals were
still not met.
10. Lockheed concluded that 4340-grade steel was the most cost-effective
material for a flywheel in a disc configuration. E-glass and S-glass
materials were found to be best suited for bar-type flywheel geome-
tries. In tests to failure, the steel wheel exceeded specified peak
speeds, while the glass materials fell short of design goals.
11. The Johns Hopkins University Applied Physics Laboratory tested ad-
vanced flywheels in filamentary and composite rod/bar configurations
with mixed results. Single-strand boron filaments, small graphite/
epoxy composite rods, and small R-glass/polyester composite rods
exceeded energy storage design goals, but the larger one-pound
S-glass/epoxy and graphite/epoxy composite bars failed to achieve
design goals; this was attributed to inadequate material processing
techniques.
12. Sundstrand determined that a combination of mechanical, hydromechan-
ical, and hydrostatic transmissions is a practical means of providing
power for the flywheel, heat engine, and drive wheel links in a hybrid
heat engine/flywheel-powered car. Computer simulation of vehicles
driven over the Federal Emissions Test Driving Cycle showed no fuel
economy advantage for the hybrid-powered automobile when compared
with a conventionally powered automobile. Mechanical Technology, Inc.,
in its transmission study, arrived at conclusions similar to Sundstrand.
13. Although not all of the goals were met, the EPA-funded programs re-
sulted in some technology advancements, a much clearer definition of
critical problem areas, and the establishment of preferable system
operating modes. While the hybrid vehicle has proven to be techni
cally feasible, it is a complex costly system when configured to
match the performance of conventional internal combustion engine-
powered vehicles.
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.REPORT NO. "
EPA-460/3-74-013-a
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
2.
3. RECIPIENT'S ACCESSION-NO.
. TITLE AND SUBTITLE
Current Status of Alternative Automotive Power
Systems and Fuels
Volume I - Executive Summary
5. REPORT DATE
July 1974
\6. PERFORMING ORGANIZATION CODE
VUT
S)
D. E. Lapedes, M. G. Hinton, J. Meltzer, T. lura
8. PERFORMING ORGANIZATION REPORT NO.
ATR-74(7325)-l, Vol. I
9. PERFORMING ORGANIZATION NAME AND ADDRESS
The Environmental Programs Group
Environment and Urban Division
The Aerospace Corporation
El Segundo, California 90245
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-01-0417
12. SPONSORING AGENCY NAME AND ADDRESS
EPA , Office of Air and Wa.ste Management
Office of Mobile Source Air .Pollution Control
Alternative Automotive Power Systems Division
Ann Arbor, Michigan 48105
13. TYPE OF. REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT '. : "~~
A summarization has been made of the available nonproprietary information on
the technological status of automotive power systems which are alternatives to the
conventional internal combustion engine, and the technological status of non-
petroleum-based fuels derived from domestic sources which may have application
to future automotive vehicles. The material presented is based principally upon
the results of research and technology activities sponsored under the Alternative
Automotive Power Systems Program which was originated in 1970. Supplementary
data are included from programs sponsored by other government agencies and by
private industry. The results of the study are presented in four volumes; this
volume presents a concise view of important findings and conclusions for three
topical areas: Alternative Automotive Heat Engines, Alternative Nonpetroleum-
Based Automotive Fuels, Electric and Hybrid Power Systems.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
Automotive Heat Engines
Automotive Nonpetroleum-Based Fuels
Electric Cars
Hybrid Heat Engine/Battery Cars
Hybrid Heat Engine/Flywheel Cars
Characterization
Exhaust Emissions
Fuel Economy
Technology Status
3. DISTRIBUTION STATEMEN1
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
>1. NO. OF PAGES
51
20. SECURITY CLASS '(Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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