AEROSPACE REPORT NO
`TOR-O059(~769-01)-2. VOL. I
`
`Final Report
`Hybrid Heat Engine / Electric Systems
`Volume l: Sections l through 13
`
`Study
`
`71 JUN ~t
`
`Prepared for DIVISION OF ADVANCED AUTOMOTIVE
`POWER SYSTEMS DEVELOPMENT
`U. S. ENVIRONMENTAL PROTECTION AGENCY
`Ann Arbor, Michigan
`
`Contract No. F04701-70-C-0059
`
`Office of Corporate Planning
`THE AEROSPACE CORPORATION
`El .Segundo, California
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`Report No.
`TOR-0059(6769-01)-2,
`Vol. I
`
`FINAL REPORT
`HYBRID HEAT ENGINE/ELECTRIC SYSTEMS STUDY
`
`Volume h Sections 1 through 13
`
`71 JUN ~1
`
`Office of Corporate Planning
`THE AEROSPACE CORPORATION
`El Segundo, California
`
`Prepared for
`
`Division of Advanced Automotive Power Systems Development
`U.S. ENVIRONMENTAL PROTECTION AGENCY
`Ann Arbor, Michigan
`
`Contract No. F04701-70-C-0059
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`
`FOREWORD
`
`Basic to analyzing the performance of the hybrid vehicle was the inlportancc
`of understanding the characteristics of each major component since each
`would be operating in a nonstandard mode required by the hybr id arrange-
`ment. In addition, the potential for improvement had to be understood to
`predict the performance of advanced designs. This report, therefore, con-
`tains two types of information: (a) hybrid system analysis and results; and
`’(b) major component state-of-the-art discussions, characteristics used in
`this study, and advanced technology assessments. Heat engine operating
`characteristics, mechanical parameters, and exhaust emissions are covered
`extensively because of both their primary importance and the difficulty
`involved in collecting a reliable comprehensive set of data; this should relieve
`future investigators making studies of nonconventional propulsion systems of
`the necessity of repeating the burdensome task of assembling a data bank.
`
`It should be recognized that calculated results are based on data compilc.d in
`this study. The magnitude and trends were established on the basis ~,l ~’,
`comprehensive survey and evaluation of the best data fronn both the open
`literature and cm’rent available unpublished data sources. 3’hese data are
`considered suitable for use in the feasibility study conducted under this c<,n-
`tract. However, for further detailed design a substantial refinement o1 the
`data base would be necessary.
`
`l&
`
`he report is organized to give a logical build-up of information starting with
`study specification, analytical techniques, and component characteristics and
`concluding with system performance results and recommendations for develop-
`ment. However, seIective reading of major systems performance results is
`possible and to assist those so interested, the following brief guide is pre-
`sented:
`
`Section i
`
`Sections 2, 3, I0, and II
`
`Sections 3 and 4
`
`Sections 6 through 9
`
`Section IZ
`
`Section 13
`
`Summary of study results and recom-
`mentations
`
`Presentation of study objectives,
`design specifications, and results
`
`Description of computational techniques
`and performance requirements
`
`Review of contemporary and projected
`technology of major components
`
`Cost estimates for high-volume pro-
`duction of hybrid cars
`
`Presentation of a technological plan for
`component and system development
`
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`This report is published in two volumes for convenience; however, separation
`of the material is made with due regard to organization. Volume 1 consists of
`Sections 1 through 13 and presents the essential study information, while
`Volume II consists of Appendices A through F and presents supplementary
`data.
`
`The period of performance for this study was June 1970 through June 1971.
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`AC KNOW LE DG MEN TS
`
`The extensive diversity in technological capabilities necessary for a thorough
`
`evaluation of the hybrid electric vehicle has required the reliance for support
`
`and expertise on select members of The Aerospace Corporation technical
`
`staff as well as members of the national technical comn~unity. Recognition
`
`of this effort is expressed herewith:
`
`The Aerospace Corporation
`
`Mr,
`Mr.
`Mr.
`
`Dan Bernstein
`Lester Forrest
`Gerald Harju
`
`Mr.
`
`Mer r ill Hinton
`
`Dr. Toru lura
`
`Mr. Dennis Kelly
`
`Mr. Jack Kettler
`
`Mr. Harry Killian
`
`Mr. Robert La France
`
`Electrical System- Control System
`Heat Engines (Internal Combustion)
`Programming for Computations
`
`Vehicle Specifications/Conceptual Des ign
`and Sizing Studies
`
`Heat Engines (Internal Combustion’)
`Heat Engine Exhaust Emissions
`Vehicle Exhaust Emissions Test Progranl
`Electrical Systenn - Motor and (]enerator
`
`Electrical Systenl - Batteries
`Heat Engines (External Combustion)
`
`Computational Techniques
`Electrical System - Batteries
`Electrical System - Motor, Generator,
`Control Systems
`
`Mrs. Roberta Nichols
`
`Vehicle Exhaust Emission Test Program
`
`Mr. Wolfgang Roessler
`
`Dr. Henry Sampson
`
`Mr. Raymond Schult
`
`Heat Engine Exhaust Emissions
`Vehicle Exhaust Emission Test Program
`
`Vehicle Specifications
`Computational Techniques
`Vehicle Power Requirements
`Electrical System - Motor, Generator,
`Control Systems
`
`University of California, Berkeley
`
`Dr. Rober t Sawyer
`
`Heat Engine Exhaust Emissions
`
`University of California, Irvine
`
`Dr. Robert M. Saunders
`
`Electrical System -
`Control Systems
`
`Motor Generator,
`
`-V-
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`It is to be noted that considerable data of great value to this study were
`
`kindly provided by individuals in industry, universities, and government
`
`agencies. Acknowledgment of these data sources is given in Appendix F
`
`to this report.
`
`Donald E.
`Manager, Hybrid Veh
`
`.~ Progr am
`
`~rograms
`Office of Corporate Planning
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`CONTENTS
`
`The major sections and appendices of Volumes I and II are listed below. For
`detailed tables of contents and lists of illustrations see the individual sections
`
`and appendices.
`
`Section
`
`Volume I
`
`I.
`Z.
`3.
`4.
`5.
`6.
`
`.
`
`8.
`9.
`I0.
`Ii.
`12.
`13.
`
`Summary ............................
`Introduction .........................
`Vehicle Specifications and Study hIiethodology .........
`Computational Techniques ..................
`Vehicle Power Requirements ...............
`Electrical System- Motor, Generator, and Control
`Systems ............................
`Electrical System - Battery Characteristics and
`Oper at[on ............................
`Heat Engine Performance Characteristics and Operation.
`Heat Engine Exhaust Emissions ................
`Conceptual Design and Sizing Studies ............
`Summary of Results ......................
`Vehicle Production Cost Comparison .............
`Technology Development Program Plan ............
`
`Page
`
`1 - 1
`Z- 1
`3-1
`4- 1
`5-I
`
`6-1
`
`7-I
`8-1
`9-1
`I0-i
`ii-I
`12-I
`13-I
`
`Append ix
`
`Volume II
`
`A,
`
`B.
`C.
`D.
`E.
`F.
`
`Hybrid Vehicle Performance Evaluation Computer
`Program ............................
`Heat Engine Exhaust Emissions Collation and Analysis ....
`Vehicle Exhaust Emissions Test Program ...........
`Vehicle Characteristics Over Emission Driving Cycle ....
`Heat Engine Data Compilation .................
`Acknowledgments to Sources of Subsystems/Component
`Data ..............................
`
`A- 1
`B-I
`C-I
`D-I
`E-I
`
`F-I
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`SECTION 1
`
`SUMMARY
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`CONTENTS
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`la
`
`SUMMARY
`
`i.i
`
`1.2
`
`1.3
`
`1.4
`
`Introduction .......................
`Study Ground Rules and Procedures ...........
`
`Summary of Results ...................
`
`i. 3. 1 Family Car and Commuter Car .......
`i. 3. Z Buses and Vans .................
`Summary of Recommendations .............
`Phase I - Detailed Hybrid System Analysis
`1.4. 1
`and Expanded Data Base .......
`1.4. Z Phase II - Component Advanced Technology .
`Phase Ill - Test Bed and Prototype Vehicle
`1.4.3
`Development ...................
`i. 4.3. 1 Recommended System
`Deve lopment .............
`1.4.3. Z Recommended Hybrid Vehicle
`System Design ............
`1.4.3.3 Recommended Component
`Development .............
`
`FIGURES
`
`I-I.
`
`Vehicle Emission Comparison, Conventional
`Operation Versus Hybrid Operation .............
`
`Con~parative Emission Levels of the Family
`and Commuter Cars .............
`
`-’3,
`
`Installed Battery Requirements and Projected
`Battery Capabilities .....................
`
`l -4.
`
`Hybrid Electric Recommended Development Schedule
`
`1-1
`
`I-I
`l-I
`I-3
`i-4
`I-Ii
`1-12
`
`1-13
`1-16
`
`1-17
`
`1-18
`
`1-18
`
`1-19
`
`I-5
`
`I-6
`
`I-9
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`1-13
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`SECTION i
`
`SUMMARY
`
`l.l
`
`INTRODUCTION
`
`This report contains the results of a comprehensive study aimed at deter-
`
`mining the feasibility of using a hybrid heat engine/electric propulsion
`
`system as a means of reducing exhaust emissions from street-operated
`
`vehicles. In this hybrid concept, the source of power is a combination of
`
`heat engine and batteries (in essence, the heat engine supplies steady state
`
`power and the batteries supply transient power demands). The study
`
`examined -- for several classes of vehicles -- many types of heat engines,
`
`batteries, and other major components, as well as several design configura-
`
`tions. Following a review of the associated technologies, hybrid perfor-
`
`mance, exhaust emissions, and major component requirements were deter-
`
`mined. Based on these results, recommendations are formulated to ensure
`
`the development of critical powertrain components for an early demonstration
`
`of prototype vehicles.
`
`1.Z
`
`STUDY GROUND RULES AND PROCEDURES
`
`In the propulsion of the hybrid heat engine/electric vehicle, the ultimate
`
`source of all energy to be expended is the heat engine. The key to success
`
`in reducing exhaust emissions is good part-load and full load efficiency of
`
`powertrain components, and the ability to restrict operational requirements
`
`for the heat engine to those of supplying road load power and (in conjunction
`
`with a generator)recharging advanced high power/high energy density
`
`batteries that supply acceleration power. With this idea in mind, the study
`
`was tailored to examine six classes of vehicles: the 4000-1b family car,
`
`1700-1b commuter car, low- and high-speed postal/delivery van, and tow-
`
`and high-speed [ntracity bus. For each class of vehicle, five engines were
`
`included in the powertrain: spark ignition, compress ion ignition, gas turbine,
`
`Rankine cycle, and Stifling cycle. Lead-acid, nickel-cadmium, and
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`nickel-zinc batteries were studied for adequacy in supplying acceleration
`
`power to each vehicle. Also, a wide range of AC and DC motors, generators,
`
`and power conditioning and control systems were evaluated for performance,
`
`efficiency, weight, simplicity, and cost.
`
`Throughout the study, the following ground rules prevailed:
`
`.
`
`.
`
`o
`
`o
`
`Conventional automotive vehicles are to be matched in
`acceleration, speed, grad,ability, curb weight, range,
`and powertrain weight.
`
`The battery is not to require external recharge. Therefore,
`the range of the vehicle is not dependent on the installed
`battery capacity. This requirement was simulated in
`computations by requiring that the heat engine-driven
`generator recharge the battery to the original state-of-charge
`prior to the end of the emission driving cycle.
`
`The battery is to discharge only when the vehicle is undergoing
`acceleration, not on a smooth grade or at cruise conditions.
`
`The heat engine is to supply steady road load power and is
`not required to undergo rapid acceleration.
`
`Only design concepts compatiblewith near term (1972-1975)
`prototype vehicle development are to be considered.
`
`With the establishment of the ground rules, the study was executed in the
`
`following manner:
`
`1
`
`.
`
`.
`
`Formulate quantitative specifications based on current
`conventional vehicle performance and design data. These
`values were coordinated with the Air Pollution Control Office
`(APCO), Environmental Protection Agency (EPA). ~’"
`
`Review contemporary and projected technology for power,rain
`components and determine performance, design, and cost
`characteristics.
`
`Evaluate conceptual designs and select a series and a parallel
`powertrain configuration for further analysis. The series
`
`Reference is made throughout this report to the DHEW (Department of
`Health, Education and Welfare) Driving Cycle, The sponsoring research
`and development office was formerly the Air Pollution Control Office and
`a part of the DHEW.
`
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`configuration is characterized by the principle that all power is
`transmitted to the rear wheels by an electric drive motor.
`The parallel configuration is characterized by the principle
`that the heat engine is mechanically linked to the drive wheels
`to supply a portion of the power required, while the electrical
`system supplies the remainder.
`
`Calculate component and vehicle power and energy require-
`ments for acceleration and steady road load.
`
`Determine battery power density and energy density require-
`ments based on realistic component weights and powertrain
`weight allocations.
`
`Calculate vehicle fuel consumption and exhaust emissions,
`based on the energy expended by the heat engine for the vehicle
`operating over the emissions driving cycle. For the family
`and commuter car, the 197Z DHEW emission driving cycle
`was used.
`
`Determine the trade-off between vehicle exhaust emissions
`and such factors as engine and battery type, battery recharge
`efficiency, electric motor efficiency, regenerative braking
`efficiency, vehicle weight, and parallel and series powertrain
`configurations.
`
`Recommend viable configurations for further study and propose
`a program designed to ensure component development for early
`demonstration of a hybrid heat engine/electric vehicle; in this
`regard, estimate both development and high rate production
`costs.
`
`.
`
`.
`
`.
`
`.
`
`.
`
`1.3
`
`SUMMARY OF RESULTS
`
`So many different types of vehicle/configuration/heat engine combinatio~s
`
`were studied that it is difficult to highlight every result shown in the body
`
`of the report; therefore, only the most important are enumerated in the
`
`following pa rag raphs.
`
`It should be recognized that the calculated vehicle exhaust emission results
`
`are based on measured engine exhaust emission data compiled during the
`
`course of this study. Engine exhaust emission magnitudes and trends were
`
`established on the basis of a comprehensive survey and evaluation of the
`
`best data from both the open literature and current available unpublished
`
`engine data sources. However, it was found that very little emission data
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`were available for the hybrid type of operation and especially for part-load
`
`engine operating conditions and for the cold start requirement consistent
`
`with the I 972 Federal Test Procedure. The resulting data are considered
`
`suitable for use in an initial feasibility study as conducted under this
`
`contract. However, in further detailed design studies, a substantial
`
`increase in the data base will be necessary for powertrain optimization.
`
`The current study data base is fully discussed in Appendix B.
`
`In addition to reflecting the engine emissions data base, the study results
`
`also reflect the use of selected battery models. The charge-discharge
`
`characteristics for lead-acid, nickel-cadmium, and nickel-zinc batteries
`
`were based on available data but modified on the basis of projections for
`
`future near-term capability. These battery models are discussed in
`
`Section 7. 3 of the report.
`
`I. 3. I
`
`Family Car and Commuter Car
`
`The following observations can be made about these classesof vehicles:
`
`.
`
`For the available powertrain weight and volume and vehicle
`performance specified for this study, only the spark ignition
`internal combustion engine {both reciprocating and rotary)
`and the gas turbine engines can be practically packaged into
`the hybrid heat engine/electric vehicle. These engines
`impose realistically achievable goals on the battery
`specifications for power and energy density.
`
`All hybrids examined showed marked calculated emission
`reductions over current conventional vehicles. This is
`i11ustrated by the results shown in Figure I-I. In this figure,
`measured cold start emission data available for a 1 970
`conventional spark ignition engine automobile is compared
`with calculated hot start emission levels for several develop-
`ment stages of a spark ignition engine in a hybrid powertrain
`automobile. In the first emissions comparison, a small
`conventional engine is used in the hybrid vehicle; the second
`comparison is for the same engine but operating over the
`restricted air/fuel ratio range noted and with exhaust
`recirculation; the third comparison is for an advanced
`technology engine operating at very high air/fuel ratio with
`exhaust gas recirculation and incorporating catalytic converters.
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`50
`
`40
`
`E
`
`= 30
`
`W
`
`W
`....J
`
`(.f)
`oo
`
`20
`
`I0
`
`0
`
`CONVENTIONAL
`S.l. ENGINE
`,,(VARIABLE AIF),
`8
`
`CONVENTIONAL
`ADVANCED
`S.l. ENGINE
`(A/F = 15-16) + RECIRC., TECHNOLOGY
`PLUS
`o ,J A/F = 22 + CAT. + RECIRC. ,,
`
`z
`
`-I- (.-.) z
`
`CONVENTIONAL
`VEHICLE
`(COLD START)
`
`HYBRID VEHICLE
`(4000-1b FAMILY CAR)
`(HOT START)
`
`Figure I-I. Vehicle Emission Comparison, Conventional Operation
`Versus Hybrid Operation (Spark-Ignition Engine,
`DHEW Driving Cycle)
`
`.
`
`.
`
`1
`
`Based on analysis, if currently available engine technology
`is used, no version of the family car could meet 1975/76
`emission standards. No catalytic converters or thermal
`reactors were added to the powertrain for this case.
`
`Calculations based on hot start with advanced engine technology
`indicates that all versions could meet 1 975/76 standards except
`for the NO2 excess for the spark ignition family car version
`(discussed in item 6) and the NO2 excess for the diesel.
`Potential diesel engine improvements that might reduce the
`NO2 emission level are discussed in Appendix B.
`
`Commuter car emissions are less than one-half of those for
`the family car and with advanced technology easily meet the
`1975/76 standards as shown in Figure 1-2. (The commuter car
`weighs only 1 700 lb and has reduced acceleration and maximum
`cruise speed capabilities.)
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`120
`
`I
`
`I00’
`
`80~
`"I-
`
`U3
`
`Z
`I---
`
`urb
`p,-
`O~
`
`6O
`
`o
`l,--
`¯ 40m
`Z
`~.~
`
`f~
`
`20--
`
`o
`Z
`
`n 2
`V
`
`I
`I
`I
`t
`
`/
`/
`/
`/
`/
`/
`
`E
`
`I975/1976 STANDARDS
`
`T
`z
`
`1975/1976 STANDARDS
`H C - 0.46 gm/mi
`I CO 4.7 grn/rni
`
`NOz-0.4 gm/mi
`ADVANCED TECHNOLOGY
`PARALLEL CONFIGURATION --
`HOT START ON DHEW DRIVING
`CYCLE
`
`I’?]c~ 8-
`-
`
`_
`
`0
`
`~. S. L . ,GAS T, URBINEj
`FAMILY CAR
`
`S.I. GAS TURBINE,,
`COMMU’IZER CAR
`
`Figure 1-2. Comparative Emission Levels of the
`Family and Commuter Cars
`
`,
`
`Calculated hot start emission results for family and commuter
`cars using spark ignition and gas turbine engines are summarized
`in Figure I-2 and compared to the 1 975/76 standards. The
`values shown are for vehicles incorporating advanced technology
`components and using the parallel powertrain configuration.
`All values meet the numerical values of the 1 975/76 standards
`(cold start), except for NO2 in the spark ignition family car,
`and even this value is very close. This standard could be
`met if vehicle specifications were revised to permit a slight
`reduction in vehicle performance and approximately a
`l 0 percent reduction in family car weight specifications.
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`10.
`
`ll.
`
`12.
`
`Emissions are sensitive to: (a) heat engine class and assunlcd
`engine emission part-load characteristics; (b) driving cycle
`characteristics selected for evaluation; (c) the engine operating
`mode used over the cycle; (d) the battery discharge and charge
`characteristics assumed for the analysis; and (e) electric drive
`motor efficiency and part load characteristics.
`
`Only spark ignition and gas turbine engine versions warrant
`intensive near term effort when availability, weight, emissions,
`and cost are considered.
`
`Emissions are approximately 1 0 and 1 5 percent lower for the
`parallel powertrain configuration as compared to the series
`configuration in the family and commuter cars, respectively.
`However, the parallel powertrain is more complex.
`Descriptions of the powertrains analyzed can be found in
`Section 1 0. 1.
`
`As noted earlier, study results are based primarily on hot
`start data. Incorporation of cold start effects, based on the
`limited amount of cold start data available, would still allow
`the advanced technology engine (very lean with exhaust treatment)
`versions of the hybrid vehicle to meet 1975 HC and CO standards.
`The NO2 emission values are reduced when cold start effects
`are incorporated. Cold start effects are discussed in Section 9.
`
`An improved lead-acid battery is needed which provides
`increased power density capabilities under shallow discharge
`operation to be used in near term hybrid applications. The
`near term application will not quite meet vehicle specifications
`for vehicle performance due to an exceeding of the powertrain
`weight allocation or due to insufficient battery lifetime. In
`order to meet all specifications, the nickel-zinc battery looks
`promising for the post-1975 period. Production costs for both
`types of batteries must be carefully considered in selection of a
`suitable battery design.
`
`Based on the powertrain and battery models assumed and the
`two driving cycles used in analysis of the family car
`(Section 3. 3), lead-acid battery development goals were generated.
`The analysis results in the goal of a 38 amp-hr battery which
`operates at less than 4 percent depth-of-discharge. Normal
`vehicle operation over the DHEW Driving Cycle requires up to
`260 peak amperes for acceleration with an average discharge
`current of about 50 amperes and a maximum energy drain of
`0.3 kw-hr (which is replenished by the generator before the end
`of the cycle). During occasional maximum vehicle acceleration
`to 80 mph, about 460 peak amperes and 0. 5 kw-hr are withdrawn
`from the battery. For a design life of 5000 hr of operation or
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`13.
`
`14.
`
`15.
`
`16.
`
`17.
`
`18.
`
`about I00,000 vehicle miles of city driving, between 900,000
`and I, 000,000 charge/discharge cycles occur (Section 7. 6).
`
`In Figure 1-3, battery power density and energy density
`capabilities are compared with installed battery requirements
`for a spark ignition, series powertrain version of a family car.
`The installed requirements for energy density are based on the
`battery charge/discharge characteristics assumed for this study
`and may vary somewhat depending on actual test data from a
`particular advanced battery design. The intersection of the
`battery capability and vehicle-required installed densities gives
`the power and energy density compatible with vehicle weight
`(and battery weight) allocation. For the lead-acid case shown,
`the maximum power density requirement ranges from 118 to
`1 50 watt/lb and the installed energy density ranges from 11 to
`14 watt-hr/lb. The vehicle weight ranges from 4200 to 4400 lb,
`which represents 600 to 800 lb of batteries; this vehicle would
`have reduced road performance. With the nickel-zinc battery,
`a 4000-1b car could be built which meets the performance
`specifications of this study. Nickel-zinc power density and
`energy density values would be approximately 230 and Z0,
`re spe ctively.
`
`Battery charge acceptance characteristics play an extremely
`important role in determining resultant vehicle exhaust
`emissions (Section 7).
`
`Regenerative braking has essentially no effect on emissions for
`the hybrid heat engine/electric vehicle due to battery charge
`acceptance limitations that preclude the ability to store the
`braking energy. Hence, the expected advantage in reduced
`generator output for recharging batteries (and therefore
`reduced engine power and emissions) did not materialize.
`
`Charge acceptance improvement goals should be at least 40
`amperes at over 95 percent state-of-charge without
`regenerative braking and as high as 400 amperes at over
`95 percent state-of-charge with regenerative braking to
`minimize emissions.
`
`Battery lifetime and charge acceptance are important areas
`for battery improvements.
`
`Vehicle weight increases of several hundred pounds to
`accommodate additional battery or engine weight have a
`minor effect on exhaust emissions, but the heavier vehicles
`would have reduced road performance.
`
`Realistically varying the battery recharge efficiency (to
`account for resistive losses and incomplete chemical
`reactions) has little effect on emissions.
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`320
`
`280
`
`240
`
`m
`¯ 200
`
`Z
`W
`"’ 160
`
`o
`0-
`
`t
`
`:::) 120
`X
`
`I I
`
`LEAD
`ACID BATTERY
`
`VEHICLE
`WEIGHT : 4000 Ib
`
`\
`\
`\
`
`NICKEL ZINC
`BATTERY
`
`INSTALLED
`BATTERY REQUIREMENTS-
`
`4 200 Ib
`
`4400 Ib
`
`4600 Ib
`B0--
`
`40
`
`FAMILY CAR
`S.I. ENGINE
`SERIES CONFIGURATION
`
`0
`0
`
`I I I 1
`I0
`20
`30
`40
`MAXIMUM INSTALLED ENERGY DENSITY, W-hr/Ib
`
`50
`
`Figure I-3. Installed Battery Requirements and
`Projected Battery Capabilitie s
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`19. Fuel consumption values for the spark ignition engine are
`summarized in the following table for all vehicles operating
`over their emission driving cycles (the 1972 DHEW Driving
`Cycle for the commuter car and the family car). The levels
`shown for the family and commuter cars are competitive with
`equivalent 1 970 conventional vehicles.
`
`Vehicle
`
`Series Configuration
`(mi/gal)
`
`Parallel Configuration
`(mi/gal)
`
`Commuter Car
`Family Car
`
`Low-speed Van
`High-speed Van
`
`Low- speed Bus
`High-speed Bus
`
`26
`II
`
`3.75
`4
`
`1.25
`1.5
`
`30. 5
`IZ. 5
`
`5
`
`Z
`
`These results were developed using specific fuel consumption
`characteristics based on the minimum SFC/rated horsepower
`correlation presented in Section 8. The data here are
`representative of current carbureted spark ignition engines
`operating at air/fuel ratios of from 14 to 16. No adjustment
`in SFC was made for the lean air/fuel ratio regimes adopted
`for hybrid operation because there is every reason to expect
`that appropriate modifications in the design of advanced engine
`systems (viz. stratified charge) will permit operation at high
`air/fuel ratios without serious degradation in fuel consumption.
`If no improvement were made, the miles per gallon at the
`very lean air/fuel ratios would be approximately 20 percent
`lower than those shown.
`
`Estimates of consumer costs for the major subsyster~is of
`an advanced hybrid vehicle in large volume production were
`prepared by judging system complexity and performance
`requirements using current hardware cost data wherever
`available. The powertrain and vehicle component cost
`estimates were then used to construct a total-vehicle-cost
`comparison between hybrid system designs for the family car
`and current (I 970) conventional family cars. As shown in
`the following table, the hybrid costs range from I. 4 to Z. Z5
`times higher than conventional cars. However, it is expected
`that the conventional car meeting the 1975 emission standards
`will be more expensive than today’s version. It should also
`be noted that the hybrid using the Diesel, Rankine, and
`Stirling engines would not meet the powertrain weight
`allocations or the performance specifications.
`
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`The tabulation results should be approached with caution, giving
`due regard to the preciseness of the assumptions made in the
`cost analysis. The hazard of assigning significance to the
`relative magnitudes of the cost ratio is apparent when it is
`recognized that to arrive at production costs it has been
`necessary to estimate figures for a number of critical com-
`ponents which at present may be barely classified as being in
`a conceptual design phase. The basis of these estimates arc
`presented in Section I 2.
`
`Vehicle
`
`Relative Costs
`
`Current Conventional Car
`
`Hybrid Car
`
`Spark Ignition
`
`Diesel
`
`Gas Turbine
`
`Rankine
`
`Sti rling
`
`1.4-1.6
`
`1.5-:.7
`
`1.6
`2+
`
`2.25+
`
`1. 3.2
`
`Busses and Vans
`
`Extensive investigation was also conducted on busses and vans ill this st,,dy.
`
`This included analysis of component requirements, vehicle performance
`
`and exhaust emission levels. The information generated on busses and vans
`
`can be found throughout this report.
`
`The following limited observations can be made about these classes of
`
`vehicles:
`
`.
`
`?.
`
`1
`
`Relative evaluations were not possible since emission
`standards, vehicle emissions test data, and realistic driving
`cycle data were not available.
`
`Emission data to be used in future hybrid evaluations were
`generated over a representative driving cycle.
`
`For the bus, battery power density and energy density
`requirements are such that batteries could be readily made
`with current technology.
`
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`1.4
`
`SUMMARY OF RECOMMENDATIONS
`
`The intent of the recommended programs presented in this report is to
`
`provide the EPA with a planning document for ensuring the early availability
`
`of a low emission, viable alternative to the conventional automotive passenger
`
`car. In this regard, a development effort has been formulated in three
`
`phases. In brief, the first phase should be aimed at a finer definition of
`
`important hybrid parameters through both expanded analysis and data
`
`collection. A study should be performed to define in greater detail the
`
`hybrid vehicle production and operating costs since costs are an important
`
`parameter in determining if the hybrid is a viable competitor to the con-
`
`ventionally powered automobile. In addition to the cost analysis, a
`
`performance analysis should be performed to a level of depth greater than
`
`was performed in this feasibility study. Acquisition of component test data
`
`is needed to support this analysis. A very important area for expanded
`
`data collection is in the engine emission area. Here, data on engines
`
`operating in the hybrid mode are needed to strengthen the data base used
`
`for analysis. Comparative analysis between cars using hybrid heat
`
`engine-electric powertrains and those using advanced engines should be
`
`made to determine the advantages or disadvantages of the hybrid concept
`
`as .Tt means of reducing auto pollution. Recommendations for additional
`
`work effort in Phases II and Ill are of course highly dependent on the
`
`results of studies conducted in Phase I.
`
`The second phase should consist of an intensive effort to develop critical
`
`powertrain components destined for a prototype vehicle. This would
`
`incI,:de advanced technology work on engines, batteries, motors/generators
`
`~d control systems designed to operate in the hybrid mode.
`
`The third phase encompasses the hardware definition and development
`
`necessary for an early test bed vehicle as well as for a later prototype
`
`vehicle. The details of each phase of the recommended work effort are
`
`summarized in the subsequent discussion.
`
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`Figure 1-4 shows a schedule of activity for the three phases of recommended
`
`hybrid heat engine]electric system efforts. More information on these
`
`recommendations can be found in Section 13 and also in Sections 6 through 9
`
`for individual components
`
`PHASE I -ANALYSIS & DATA
`ACQUISITION
`PERFORMANCE ANALYSIS
`DATA ACQUISITION
`COST ANALYSIS
`POWERTRAIN COMPARISONS
`DECISION WHETHER TO
`PROCEED WITH TEST BED
`PHASE Ill - ADVANCED TECHNOLOGY
`RESEARCH
`DEVELOPMENT
`PHASE m-SYSTEM HARDWARE
`TEST BED
`PROTOTYPE
`
`:-r~l
`
`r--1
`Z
`
`"_---__L__
`
`YEARS
`3
`
`I
`
`I
`
`I
`I I I
`
`!
`
`Figure 1-4. Hybrid Electric Recommended Development
`Schedule
`
`1.4.1
`
`Phase I - Detailed Hybrid System Analysis and
`Expanded Data Base
`
`A logical progression from the current feasibility study would be a study
`
`directed at an in-depth analysis of the hybrid vehicle powertrain in a
`
`passenger car application. Thus, in a study narrowed in scope, the more
`
`intricate details of component operation and installation in the vehicle can
`
`be examined. The analysis is fundamental to establishing a firmer basis
`
`for objective evaluation of the hybrid electric vehicle in terms of exhaust
`
`emissions and costs when compared to present and projected versions of
`
`the engine-driven passenger car.
`
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`A major effort in the study program should be the establishment of an
`
`expanded data base for the powertrain components. This could be
`
`accomplished in two ways: (I) through planning and conducting of tests on
`
`specifi