Future Light-Duty Vehicles:
Predicting their Fuel Consumption and Assessing their Potential
by
Felix F. AuYeung
B.S. Mechanical Engineering
University of California, Berkeley, 1998.
Submitted to the Department of Mechanical Engineering
in partial fulfillment of the requirements for the Degree of
MASTERS OF SCIENCE
at the
Massachusetts Institute of Technology
June 2000
©2000 Massachusetts Institute of Technology.
All rights reserved.
MASSACHUSETTS INSTITUTE
OF TECHNOLOGY
SEP 2 0 2000
LIBRARIES
Signature of Author: .............................................................
Departmen o'Meicanljal Engineering
May 22, 2000.
JohA B. Heywood
Certified by: ................................................................
Sun Jae Professor of Mechanical Engineering
Director of Sloan Automotive Laboratory
evisor
'uw
A ccepted by:
........................................................
.........-
.......---- --.......--
--
Ain A. Sonin
Professor of Mechanical Engineering
Chairman, Department Committee on Graduate Students
FUTURE LIGHT-DUTY VEHICLES:
Predicting their Fuel Consumption and Assessing their Potential
by
Felix F. AuYeung
Submitted to the Department of Mechanical Engineering on May 22, 2000,
in partial fulfillment of the requirements for the Degree of Masters of Science
ABSTRACT
The transportation sector in the United States is a major contributor to global energy
consumption and carbon dioxide emission. To assess the future potentials of different
technologies in addressing these two issues, we used a family of simulation programs to
predict fuel consumption for passenger cars in 2020. The selected technologies that have
good market potential and could be in mass production include: advanced gasoline and
diesel internal combustion engine vehicles with automatically-shifting clutched
transmissions, gasoline and diesel hybrid electric vehicles with continuously variable
transmissions, direct hydrogen, gasoline and methanol reformer fuel cell hybrid electric
vehicles with direct ratio drive, and battery electric vehicle with direct ratio drive.
Using a number of researched assumptions and input variables detailed in the report,
calculations were performed to estimate the energy consumption and carbon emission of
the different technologies. Comparing the results for the vehicle driving cycle only, an
evolutionary fuel consumption improvement of about 40 percent can be expected for the
baseline gasoline car, given only market pressures and gradual regulatory requirements.
With more research and investment in technology, an advanced gasoline car may further
reduce fuel consumption by 14 %, and a gasoline electric hybrid by 40 %, as compared to
the evolutionary car. Diesel versions of the advanced combustion and hybrid vehicles
may be 10-15 % better than their gasoline counterparts. Meanwhile, a direct hydrogen
fuel cell electric hybrid vehicle may have the greatest improvement over the baseline at
60 %, but the gasoline and methanol reformers fuel cell versions may be very expensive
and offer little benefit. Finally, aside from battery limitations, the electric vehicle is
difficat b
to other vehicles without taking into account the fuel cycle.
Thesis Supervisor: John B. Heywood
Title: Sun Jae Professor of Mechanical Engineering
AuYeung
2114
for my loving parents
I know there were a great many moments of concern
during my growth here, and I know you are wishing
for a Ph.D. instead, but thank you for your constant
concern, understanding, and support from the very
beginning of my life. My education will continue, and
in knowing, I must also continue to act. Perhapsyou
realize too that this purple sheep has embraced the
ideals of justice and compassion which you embody.
Acknowled2ment
I would like to thank the members of the Energy Lab research team for their insights,
encouragement, understanding, and patience: to Tobi Muster, who joined us mid-way
from Switzerland and reminds us that life has to be lived; to Darian Unger, who was our
wonderful, messy, barbecue-throwing office-mate and reminds me of the political reality
of the world; to Dr. Andreas Schafer, who juggles a dozen simultaneous assignments
with skill and was always constructively encouraging of my work; to Dr. Mal Weiss, who
keeps all of us on time (more or less) with grace and provided us with technical sanity
checks; to Dr. Lis Drake, who represents the social ramifications of our work and gladly
discussed social issues of interest to me; and of course, to my advisor Professor John
Heywood, who works harder than any man I know and has been most receptive and
supportive of all my work.
I would also like to thank others of the MIT community who made my experience here
for the past two years so enjoyable and worthwhile, including the members of: the SAVE
Environmental Club, the Solar Electric Vehicle Team, the Dr. Martin Luther King Jr.
Celebration Planning Committee and Design Seminar, the Environmental Programs Task
Force, and the Social Justice Cooperative. The many people whom I have met here and
grown to love give me strength and hope that the struggle for a more just and peaceful
world is one with many participants, rich with imagination, energy, and solidarity.
AuYeung
1/46
FUTURE LIGHT-DUTY VEHICLES:
Predicting their Fuel Consumption and Assessing their Potential
by Felix F. AuYeung
TABLE OF CONTENTS
1.0
2.0
Introduction
Road Transportation Technologies
2.1
PrecautionaryPointers
2.2
Approach, and Vehicle Concepts Examined
3.0
Simulation Model Structure
3.1
Driving Cycle
3.2
Vehicle Simulation Logic
4.0
Component Details
4.1
Vehicle Body
4.1.1 Variables and Assumptions
4.1.2 Compounding Effects in Mass Reduction
4.2
Gasoline/Diesel Combustion
4.2.1 Variables and Assumptions
4.2.2 CurrentAverage PassengerCar
4.3
Battery Electric
4.3.1 Variables and Assumptions
4.3.2 InteriorSpace and Energy Storage Capability
4.4
Gasoline/DieselElectric Hybrid
4.4.1 VariablesandAssumptions
4.4.2 Engine/BatterySize Matching
4.5
Fuel Cell Electric
4.5.1 Variablesand Assumptions
4.5.2 Reformer Properties
5.0
Vehicle Simulation Results
5.1
Vehicle System Comparison
5.2
Verification with Available Data
5.3
Battery Projection
5.4
Vehicle Load Sensitivity
5.5
EstimatedRetail Price
6.0
Vehicle Technology Conclusions
6.1
Study Intentions
6.2
Technology Highlights
6.3
Vehicle Cycle Summary
7.0
Societal Implications
7.1
Accompanying Penalties
7.2
Self-ConstructedProblem
7.3
Civil Response
Appendices and References
AuYeung
6
6
9
13
24
32
36
41
4/4'.6
TABLE OF FIGURES
Figure 1: Powerplant and fuel combinations examined
8
Figure 2: Federal Testing Procedure city and highway driving cycles
10
Figure 3: Calculation logic: mechanical drivetrain
11
Figure 4: Calculation logic: battery electric drivetrain
11
Figure 5: Calculation logic: ICE - battery electric parallel drivetrain
12
Figure 6: Calculation logic: fuel cell - battery electric drivetrain
12
Figure 7: Mass distribution by component for vehicles examined
14
Figure 8: Performance maps for current and 2020 gasoline and diesel engines
17
Figure 9: Torque and power characteristics for a 60 kW motor
19
Figure 10: Toyota Prius power curve
21
Figure 11: Hybrid power configuration comparison
22
Figure 12: Hydrogen fuel cell hybridization
23
Figure 13: Fuel cell efficiency for a 60 kW stack
24
Figure 14: Summary results for test vehicles
26
Figure 15: Brief comments on variables listed
27
Figure 16: Simulation verification with existing vehicles
28
Figure 17: Comparison of fuel economy results with existing data
29
Figure 18: Battery impact on vehicle mass and energy consumption
30
Figure 19: Consumption sensitivity to increased load
31
Figure 20: Price summary relative to carbon emission
31
Figure 21: Mass-specific costs of baseline vehicle and historical development
43
Figure 22: Retail price estimates of the ten examined vehicles
44
TABLE OF ABBREVIATIONS
brake mean effective pressure
BMEP
continuously variable transmission
CVT
electric vehicle
EV
fuel cell
FC
Federal Test Procedure
FTP
internal combustion engine
ICE
nickel metal hydride
NiMH
oxides of nitrogen
NOx
state of charge
SOC
* other abbreviations and symbols will be explained in text
AuYeung
5/4 6
FUTURE LIGHT-DUTY VEHICLES:
Predicting their Fuel Consumption and Assessing their Potential
Passenger Car Design, Performance, and Costs in 2020
1.0 Introduction
The transportation sector, especially in the industrialized world, is a major sink of energy
and a major source of anthropogenic carbon dioxide, a greenhouse gas associated with
global climate change. A disproportionate imbalance of resources and pollution can be
best demonstrated by the United States: with less than 5% of the world's total population,
it consumes 25% of the world's energy production] and generates 25% of the world's
carbon emissions. Within the U.S., where 25% of the world's cars and trucks reside and
operate, 25% of the national energy used goes to transportation.2
In an effort to conserve common depletable resources and to avoid adverse local and
global environmental changes, a research team in the Massachusetts Institute of
Technology Energy Laboratory has set out to assess the future of different types of
potential passenger vehicle technologies, to compare their relative well-to-wheels energy
consumption in a complete life-cycle analysis, and to identify possible barriers to
implementation. This paper details the component of the comprehensive report dealing
with the vehicle driving simulation and the vehicle-to-wheels fuel consumption results.
In this section of the report, we focus on the design criteria, vehicle performance, and
ownership costs of future light-duty passenger cars for the U.S. market. We will describe
the design choices for future vehicles, the rationale for projecting technological advances,
and the key assumptions for the calculations, then report on the results and analyses.
2.0 Road Transportation Technolo2ies
The current (1997) passenger vehicle fleet size in the United States is about 125 million
passenger cars and 201 million total vehicles with light trucks; the total fleet number has
increased over the past years, rising from 167 million in 1987 and 128 million in 1977,
with the light truck fleet size increasing steadily, and currently composing of almost 38 %
of the total passenger vehicles. The average vehicle miles traveled per year (1996) was
11,314 miles for cars, which has increased from 10,277 per year since 1990. This fleet of
light-duty passenger cars uses about 10% of the total energy consumed and releases about
11% of the total carbon dioxide emitted in the U.S. 3
Attempts to evaluate the potential of automobile fuel efficiency improvements started in
the early 1970s. Prompted by the two oil shocks, and, more recently, by environmental
and climate change concerns, these efforts contributed, step by step, to the growing field
of automotive technology assessment. We recognize some of the key lessons from prior
reports before beginning to report our results.
AuYeung
2.1 Precautionary Pointers
First, the intent to assess vehicle technology potentials and impacts is only possible by
taking into account both the fuel and vehicle cycles. For example, the hydrogen fuel cell
vehicle and the battery electric vehicle are both classified as zero-emission when only the
vehicle cycle is considered. However, the inclusion of the fuel cycle, i.e. how the
hydrogen and electricity are generated, reveals that although the technologies can still
potentially be clean, zero-emission becomes rather unlikely.
Second, in simulations to predict fuel consumption and carbon emission, there is an
obvious sensitivity in the calculation results to assumptions concerning the performance
characteristics of key vehicle and propulsion system components. The optimism of
technological progress must also be weighed against the cost of the new technology.
However, a range of varying assumptions will also show the great potential that exists for
reducing energy consumption in vehicles.
Finally, it is also useful to summarize three broad precautions: 4
(i) The steady improvement of the baseline or mainstream technology over time (e.g.
improved steels, better performing internal combustion engines) is usually
underestimated.
(ii)
The performance of new technology is usually overestimated, and an assessment
of the more pragmatic, often difficult to quantify but important attributes (e.g.
start-up time, refueling ease) is often omitted.
(iii)
Assessments of the time required to develop and design mass-production feasible
versions of new automotive technologies have consistently been too optimistic.
2.2 Approach and Vehicle Concepts Examined
We have examined several potentially promising future powerplants and vehicle
technology combinations using a propulsion system in a vehicle computer simulation.
This simulation "drives" the vehicle through a specified driving pattern or cycle, and
calculates the fuel consumed and thus the carbon dioxide emissions produced. Inputs for
the calculations are the vehicle driving resistance (mass or inertia, aerodynamic drag, and
tire rolling friction), and the operating characteristics of each of the major propulsion
system components (e.g. engine and transmission performance and efficiency for a
standard internal combustion engine). These vehicle fuel consumption predictions are
made for 2020, for technologies that could plausibly be in mass production at that time.
Their estimated performance characteristics relative to today's performance include
improvements that we judge could be implemented in production by 2020. However, the
more sophisticated of these concepts, which could provide substantially improved fuel
economy, are likely to be significantly more expensive.
The response of vehicle purchasers and users to these more fuel efficient but more
expensive vehicles is uncertain, and market acceptance (whether encouraged by
regulation or tax incentives or not) is essential for any large scale production. Thus, our
predictions indicate the fuel consumption and C0 2 -reducing potential of various future
AuYeung
7/4-6
propulsion systems and vehicle technologies, and do not express our judgments about
either the desirability or the likelihood of these various technologies being in large scale
production by 2020.
The vehicle and powerplant technologies we examine include the following.
Powerplants: improved gasoline and diesel internal combustion engines with mechanical
drivetrain; gasoline and diesel internal combustion engines in a parallel hybrida system
utilizing both mechanical and electric power plants; gasoline, methanol, and hydrogen
fueled fuel cell hybrid systems with electric drivetrain; and pure battery electric
drivetrain. Vehicle Technologies: various lighter-weight materials for chassis and body;
more efficient vehicle auxiliary systems; lower aerodynamic drag body shapes; lower
rolling resistance tires.
These technologies were chosen from a larger set of possible powertrain and vehicle
developments as having the highest potential for reaching production and the market.
Examples of technologies examined but then excluded from this study are natural gas
internal combustion engines, and series electric hybrids featuring turbine propulsion and
natural gas combustion engines, due to their more limited potential. Figure 1 categorizes
the combinations of propulsion system (power unit and transmission) and fuels examined
into three families: mechanical, hybrid, and electrical.
FAMILY
TRANSMISSION
POWER UNIT
FUEL
Mechanical
Auto-Clutch
Spark Ignition ICE
Gasoline
Compression Ignition ICE
Diesel
Dual
Continuously
Variable
ICE with Batteries and
Electric Motor
Gasoline, Diesel
Electrical
Single Ratio
Fuel Cell (with reformer
for gasoline, methanol)
Gasoline, Methanol,
Hydrogen
Battery
Electricity
Figure 1: Powerplant and fuel combinations examined
An important issue in this future passenger car technology assessment is the relevant
baseline. We have used as a baseline an evolutionary mid-size US passenger car: i.e., a
steadily improving gasoline-fueled spark-ignition engine, a more efficient conventional
technology transmission, and low cost vehicle weight and drag reductions. These baseline
technology improvements are based on historical and current technology trends, and are
projected to 2020. The baseline vehicle represents the likely average passenger car
In the parallel hybrid system examined here, both the engine and the battery, in parallel
via a mechanical
transmission and electric motor, respectively, can drive the wheels. See Section 4.4.
a
AuYeung
8/46
technology in 2020 that will not incur extra costs other than those necessary to keep up
with the market. Features of the baseline vehicle are distinguished from the advanced
vehicle in section 4.3.1.
A second issue is the performance and operating characteristics of these various vehicle
and powerplant combinations. Ideally, each combination should provide the same (or
closely comparable) acceleration, driveability, driving range, refueling ease, interior
driver and passenger space, trunk storage space, and meet the applicable safety and air
pollutant emissions standards.
Only some of these attributes can be dealt with quantitatively now. All propulsion system
and vehicle combinations are adjusted to provide the same ratio of maximum power to
total vehicle mass, and provide at least 600 km driving range, except for the special case
of the pure electric vehicle, whose battery constraints will be discussed later. The vehicle
size (including vehicle frontal area for drag estimation) is roughly constant. Driveability
issues (e.g. ease of start up, driving smoothness, transient response for rapid
accelerations, hill climbing, and load carrying/pulling capacity) have not yet been
assessed quantitatively for several of these technologies, though we do evaluate some of
them in Section 6. The emission levels projected to 2020 with these various technologies
also have not yet been quantified. We assume that the strictest current emissions
standards (California LEV II, EPA Tier II) for 2004 to 2008 may be further reduced in
the following decade, but that these levels can potentially be met by improved exhaust
gas treatment technology for internal combustion engines, and are within expectations for
fuel-cell systems. This assumption is least certain for the diesel ICE. We return to this
question later in Section 6.
The next two sections address the simulation structure and logic as well as the
assumptions made about component performance.
3.0 Simulation Model Structure
To estimate fuel consumption to compare various vehicles with different propulsion
systems, a family of Matlab Simulink simulation programs was used. Originally
developed by Guzzella and Amstutz5 at the Eidgen6ssiche Technische Hochschule (ETH,
Zurich), these programs back-calculate the fuel consumed by the propulsion system by
driving the vehicle through a specified cycle. Such simulations require performance
models for each major propulsion system component as well as for each vehicle driving
resistance. The component simulations used, which are updated and expanded versions of
the Guzzella and Amstutz simulations, are best characterized as aggregate, quasi-steady,
engineering models which quantify component performance in sufficient detail to be
reasonably accurate, but avoid excessive detail which would be difficult to justify for
predictions relevant to 2020. Nonetheless, a substantial number of input variables must be
specified for each element or component of the overall model. It is not the intent of this
report to document all the details of this simulation here, but rather to provide a basic
functional description of the total model.
AuYeung
9/4.6
3.1 Driving Cycle
The first critical component of the simulation is the driving cycle on which all the vehicle
calculations are based. For this study, the Federal Test Procedure (FTP) urban (city) and
highway driving cycles are used, as shown in Figure 2. These cycles are the ones used by
the Environmental Protection Agency (EPA) to measure the emissions and fuel
consumption of vehicles sold in the U.S. The results from such tests are reported each
year in the EPA Fuel Economy Guide,6 after multiplying by an empirically determined
factor (0.90 for the city cycle and 0.78 for the highway cycle) to take into account
additional real-life driving factors. The results presented in this report have not been
multiplied by these empirical factors.
FTP City Driving Cycle
30
K-
OOM
20-
10
0.
-
U
0
1
-
1
l
i
1500
1000
500
i
.
2000
Time (s)
FTP Highway Driving Cycle
30
20
U)
0n
.......
...
....
...
........
..
...
10
0
200
0
600
400
800
1000
Time (s)
Figure 2: Federal Testing Procedure city and highway driving cycles
AuYeung
10/46
3.2 Vehicle Simulation Logic
Driving
Cycle
Vehicle
Resistance
Transmission
Combustion
Engine
Fuel
Consumption
Figure 3: Calculation logic: mechanical drivetrain
The base vehicle with an internal combustion engine coupled to a mechanical
transmission is related to the specified driving cycle as shown in Figure 3. The
calculation starts with the chosen driving cycle, specified as an array of vehicle velocity
with time (at intervals of one second). From these two inputs, the vehicle acceleration is
calculated. This information is used to calculate the instantaneous power needed to
operate the vehicle, by adding aerodynamic drag, tire rolling resistance, and inertial force
(vehicle mass times acceleration). The required total power is converted to the torque
needed to drive the tires, which through an automatic, manual, or continuously variable
transmission is converted to the torque needed at the engine output shaft.
In addition to the power required as engine output, all the engine losses (due to engine
cycle inefficiencies, engine friction, changes in rotational kinetic energy, and auxiliary
component power requirements) are summed together to obtain the total rate at which
fuel chemical energy is consumed. Using the lower heating value (the stored useable
chemical energy of a fuel), this "fuel power" is converted to the amount of fuel needed,
thus generating the desired result-energy consumption per unit distance traveled. This
logic diagram applies to the current, evolutionary gasoline, and the advancedb gasoline
and diesel vehicles presented in this study.
Driving
Cycle
Vehicle
Resistance
Electric
Motor
Battery
Status
Figure 4: Calculation logic: battery electric drivetrain
The electric vehicle with batteries driving an electric motor is modeled in a similar
manner, as shown in Figure 4. In many ways, this electric vehicle is simpler, having a
single gear transmission and predictable motor and battery characteristics. Again, the
model begins with the chosen driving cycle and takes into account vehicle resistances.
Then, the total required energy at the tires is converted to the torque needed at the output
of the electric motor. With the motor efficiency and the discharging efficiency of the
batteries, the desired energy consumption per unit distance traveled can be calculated.
With an electric drivetrain, regenerative braking- the conversion of vehicle kinetic
energy to stored energy in the batteries during vehicle braking, with losses due to
generator (motor) and recharging inefficiencies-is included here also.
b Here, "advanced" is used to denote components where plausibly practical new technologies which
improve performance have been incorporated.
AuYeung
1,1 46
This logic diagram applies only to the pure battery electric vehicle, a case presented in
this study primarily for reference. Limits in battery technology (low energy storage per
unit weight, limited life, and high cost) currently prevent such vehicles from being
commercially viable, except for special niche applications. Also note that the energy
consumption for the EV will be lower than that of an ICE vehicle, because the efficiency
of the motor and battery combined is substantially higher than that of any "engine".
However, this tank to wheels estimate does not take into account the efficiency of
electricity generation and transmission over the grid, or electricity generation at a local
recharging station, nor the losses during the battery recharging process.
Driving
Vehicle
Logic
Cycle
Resistance
Control
4O
Electric
MotorBattery
Fuel
Consumption
Combustion
Transmission
Engine
ME
Batr
Figure 5: Calculation logic: ICE - battery electric parallel drivetrain
The parallel hybrid simulation combines the logic of these two models and uses both the
combustion engine and the electric motor, as shown in Figure 5. The additional logic
control block determines the power flow required from the engine and the battery, based
on the amount of power required and the state of charge of the batteries. The objective
here is to operate the engine at higher loads where it is more efficient, switch the engine
off during idling and low power requirements, and use the battery and engine together at
peak power levels so both components can be kept as small and light as possible.
Fuel Cell
Driving
Cycle
Vehicle
Resistance
Electric
Motor
C
Fuel
Consumption
Logic
Control
n *~ [Battery
Figure 6: Calculation logic: fuel cell - battery electric drivetrain
The fuel cell hybrid vehicles combine a fuel cell system with a battery pack, for similar
reasons as that of the ICE parallel hybrids: to maintain fuel cell operation in its high
efficiency region (part load in this case) as much as possible, and benefit from
regenerative braking energy recovery. Its logic is shown in Figure 6. During idling and
low-power operation, the batteries supply the necessary power. Over a certain threshold,
the fuel cell turns on; extra power is used to recharge the batteries if they are below a set
AuYeung
12/4-16
state of charge. When the power required exceeds the maximum fuel cell stack
capabilities, the batteries again supplements peak loading. Since the fuel cell directly
converts chemical energy to electrical energy, a mechanical transmission is not required.
Also, the fuel cell requires energy during vehicle operations, even when it is not
supplying power directly; hence it creates an addition drain on the battery system.
Finally, if a liquid fuel (methanol or gasoline) is stored on the vehicle, then a fuel
reformer system which converts the liquid fuel to hydrogen is included on board.
4.0 Component Details
As explained in Section 2.2, the vehicles examined in this study are designed to be
functional equivalents of today's average passenger car': a mid-sized family sedan such
as the Toyota Camry. For the customer, this means the usable interior space capacity and
vehicle performance are maintained in future vehicles. A volumetric analysis should be
performed to ensure that the propulsion and fuel systems of the advanced vehicles do not
take up excessive space; we have not done this due to limited information on propulsion
system, component size, and layout. However, ICE hybrid systems, fuel-cell systems
(with reformers or with on-board hydrogen storage) are likely to be at a disadvantage
here. Also, to ensure equal performance, all vehicles are designed to have an equal peak
power to mass ratio of 75 W/kg, which is approximated to today's value. This ratio
roughly equalizes vehicle performances, as can be checked with acceleration calculations.
The components, and key model component inputs and details, that come together to
form the total vehicle system are described below. We first focus on the vehicle body
itself, then focus on each propulsion system technology and its specifications.
4.1 Vehicle Body
The baseline reference vehicle is projected to incorporate evolutionary changes necessary
to keep up in the automotive market, while all other vehicles studied in this report
undergo advanced body changes that would be more appropriately matched to the
advanced propulsion systems involved. The main difference between the evolutionary
and advanced passenger car vehicle body is the extent to which more radical and
expensive new technologies are used to reduce vehicle mass. Andreas Schafer of the
research team performed the analysis on vehicle mass projection and distribution, as
presented in Figure 7 and explained in Appendix A.
A separate compilation study of 1996 passenger cars was performed to determine the median vehicle and
average characteristics numbers for models sold in 1996. This MIT Energy Laboratory study has not yet
been published, but some results are discussed in section 4.2.2.
AuYeung
13/46
Figure 7: Mass Distribution by Component for the ten vehicles examined. Other body parts: hinges, locks, gauges, brackets, springs, etc.;
accessories: cooling, fuel pump, fuel system; interior (1): carpets, instrument panel, restraint system, int. panels; HVAC: heating and ventilation,
air conditioning; other electronics: windshield wipers, lights, electronics and cables, window regulators, radio; other fluids: washing liquid.
Body Structure
Other Body Parts
Glazing
Chassis
Suspension and
current
baseline
advanced
advanced
advanced
advanced
advanced
advanced
advanced
SI ICE
SI ICE
SI ICE
CI ICE
SI Hybrid
CI Hybrid
FC Hybrid
FC Hybrid
FC Hybrid
Electric
gasoline
auto
gasoline
auto-clutch
gasoline
auto-clutch
diesel
auto-clutch
gasoline
CVT
diesel
CVT
gasoline
direct
methanol
direct
hydrogen
direct
electricity
direct
350
33
35
273
115
298
28
33
232
98
228
21
33
216
98
228
21
33
222
98
228
21
33
229
98
228
21
33
238
98
228
21
33
286
98
228
21
33
267
98
228
21
33
248
98
228
21
33
246
98
22
63
45
28
19
54
20
26
392
19
54
20
26
16
261
247
19
54
20
26
6
299
19
54
20
26
13
323
19
54
20
26
22
360
19
54
20
26
70
562
19
54
20
26
51
490
19
54
20
26
32
418
19
54
20
26
30
411
164
103
94
148
68
108
20
20
75
304
70
249
66
209
65
77.5
53
19
56.0
52.6
49.2
325.7
advanced
Frame
Steering
Brakes
Wheels
Tires
Extra Support
Propulsion System
Engine
Electric Motor
Fuel Cell System
Reformer
Accessories
22
19
19
19
19
Battery
12
12
12
12
100
100
Electronics
2
2
2
2
2
2
38
32
32
32
32
32
90
11
40
13
50
7
23
13
50
7
19
13
50
6
17
13
50
5
14
13
50
5
12
13
20
7
23
20
10
36
20
70
3.5
20
188
80
76
32
199
80
67
32
20
6
38
2
5
25
1125
199
80
67
32
20
6
38
2
5
25
1019
199
80
67
32
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6
38
2
5
25
1076
199
80
67
32
20
6
38
2
5
25
1108
199
80
67
32
20
6
38
2
5
25
1154
179
80
67
32
179
80
67
32
179
80
67
32
179
80
67
32
6
38
2
5
25
1383
6
38
2
5
25
1292
6
38
2
5
25
1201
6
38
2
5
25
1192
Exhaust System and
Emission Control
Gear Box
Fuel Storage System
Fuel
Engine Oil, Cooling
Water, Gear
Oil
Interior
Interior (1)
Seats
HVAC
Sound Damping
Exterior
Other Electronics
Other Fluids
Paint
Crash Safety
TOTAL VEHICLE
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7
38
2
5
1322
1
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4.1.1 Variables and Assumptions
Based on Figure 7, the total vehicle mass is subdivided into four subsystems for
comparison: chassis and body, propulsion, battery, and fuel. The chassis and body system
mass include everything for an un-powered free-rolling vehicle, including the fuel system
without the fuel as well as all structural reinforcement for extra component masses on the
vehicle. The propulsion system mass include the engine, electric motor, fuel cell system
and reformer system, all scaled according to the desired power output, as well as the
transmission, allocated a fixed mass for each option of automatic manual, continuously
variable, and direct gear.
The battery and fuel mass are also separated for ease of reference. The battery pack size
is determined by the maximum power required by the electric motor in a particular
vehicle, resulting directly in a specific battery mass and volume. This sizing assumption
does not take into account the voltage and current balance that may affect the motor
selection and performance.
The amount of energy the battery pack can store is thus also constrained; this limit has
less impact for hybrid systems because the battery pack can be recharged while driving,
although care must be taken in the case of sustained peak power supplement to ensure
that safe passing and hill climbing are possible.
The pack size or volume occupied by the battery system is also of concern because of
space limitations on board the vehicle. A volumetric analysis should be performed to
determine if the battery pack will fit in the vehicle of a certain passenger and cargo
interior volume; and if not, the appropriate penalty in aerodynamic drag factor (CdA)
should be taken into account.
The fuel mass is the amount of fuel needed to achieve approximately a minimum range of
600 km in the combined cycle. Except for the pure electric vehicle, whose special case
will be discussed in section 4.3, all vehicles exceed the 600 km range criteria.
An occupant mass is added to the total raw vehicle mass. It is the estimated average load
for a vehicle, held constant for all vehicles in this study at 110 kg, the mass of 1.5 adults
at 70 kg per person, with 5 kg of cargo. Therefore, the total operating vehicle mass is the
summation of the chassis and body system mass, the propulsion system mass, the battery
mass, the fuel mass, and the occupant mass.
Other key simulation variables, with their assumptions and descriptions, are listed below.
Aerodynamic Drag Coefficient Cd:
Aerodynamic drag coefficient is a
dimensionless number describing the drag induced by a solid traveling in a fluid
at a known relative velocity. For this study, the current vehicle has an estimated
Cd of 0.33, improving to 0.27 in the evolutionary vehicle and 0 .2 2 d in the
advanced vehicle, both in 2020.
dFord 7 and
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GM 8 have already built family-size prototypes that achieve below 0.22 for the PNGV program.
15/46
Cross-Sectional Area A,: Vehicle Cross-sectional area is the largest area in a
plane perpendicular to the direction of vehicle motion. When multiplied by Cd, air
density, and the square of the relative velocity, the product is the aerodynamic
drag force that must be overcome for the vehicle to move at that speed. Note that
in this study, it is assumed there is no wind and; the air is still.
Fdrag = 1/2PCdAxV 2
Rolling Resistance Coefficient Crr:
Rolling resistance coefficient is a
dimensionless number used to characterize the energy loss due to friction between
the road and the tires. It is multiplied by the total vehicle weight to obtain the tire
resistance force.
Fro,, = CrrMtotg
Transmission Efficiency U7trans: Transmissions are modeled with a constant
efficiency during all modes of operation, although in practice the efficiency varies
among gears. Idling in neutral or in drive (where friction is about double that in
neutral) is taken into account, but shifting losses are not. More details on
transmission performance could be added in the future; assuming an overall
constant efficiency adequately incorporates the losses at this stage.
Five different transmissions are used for this study. For today's vehicle, a 5-speed
manual at 90 % efficiency, and a 4-speed automatic at 70 % city and 80 %
highway are used to approximate the accuracy of the model. The future
evolutionary and radical gasoline and diesel vehicles use 5-speed automaticallyshifting clutched transmissions at 88 % efficiency, while future radical gasoline
and diesel hybrids use continuously variable transmissions also at 88 %9. The
benefit from the CVT is that it enables improved engine efficiency by selecting
the higher efficiency regions of the engine performance map. Finally, all the
electric-drive vehicles, the fuel cell and battery electric vehicles, operative on
single ratio direct drive at a speed and power dependent efficiency that averages
out to about 93% over the combined cycle.
Auxiliary Load Pau: Auxiliary load is assumed to be constant at 400 W during
all times of vehicle operation for all vehicles. While future vehicles may be more
efficient in power electronics, they may also have more on-board electronic
systems, possibly drawing even more power. Since the load is constant for all
vehicles and on-board systems apply to all vehicles, this study has not focused on
determining the auxiliary load more precisely.
4.1.2 Compounding Effects in Mass Reduction
Compounding effects play an important, self-reinforcing role in vehicle mass reduction.
By reducing body mass and lower vehicle resistances, a smaller and lighter power unit
can be chosen to meet the predetermined performance criteria, hence reducing the
structural mass and inertial and rolling resistances even further. All technologies benefit
from these compounding effects, some more than others.
AuYeung
4.2 Gasoline/Diesel Engines and Transmissions
The performance characteristics of both gasoline and diesel internal combustion engines
are well documented. Historical improvement trends, combined with an assessment of
likely practical technologies available over the next two decades, are used to predict the
performance of these two engines in year 2020. In the model, appropriate assumptions
obtained from this logic were used to create an engine performance map.
4.2.1 Variables and Assumptions
Engine Torque Curve: A typical maximum torque curve was constructed for a
1.6 L gasoline engine and a 1.7 L turbo diesel engine. These torque-rpm curves
can be scaled over a range of engine displacements, and define the performance of
actual engines today.
To project forward, historical trends correlating the ratio of gasoline engine power
to displaced volume against year10 show a nearly linear improvement of about
0.5% per year. Future technological improvements such as increasing use of
variable valve timing, direct injection, and reduced friction are expected to
continue this trend. Hence for 2020, the wide-open-throttle (WOT) torque for
these engines is increased by 10% overall.
Gasoline engines are expected to operate and generate peak power at a higher rpm
with these and similar advancements. Thus, an extra cumulative 1% increase was
added at each 500 rpm interval as engine speed increases for a 20 % increase at
maximum power, as shown in Figure 8.
Diesel BMEP Curve
Gasoline BMEP Curve
1600-
U1_
IL
to
1400.
IL
1400..
1200
1200.
1000*
a)
cc
C
cc
800-
le
cc
600:
400.
200
1600
-Current
(1995)
Future (2020)
-
D
10200
2000
3000
p
p
4000
5000
Engine Speed (rpm)
800
600
400-
-.
.
- Current (1995)
-0-Future (2020)
..........
..
........................
200-
-
0'
1000
A,
6000
0
1000
2000
3000
4000
5000
Engine Speed (rpm)
Figure 8: Performance maps for current and 2020 gasoline and diesel engines.
AuYeung
17/46
6000
Efficiency Map: Combustion engine efficiency maps were modeled using a
constant indicated energy conversion efficiency (fraction of fuel chemical energy
transferred to the engine's pistons as work) and a constant friction mean effective
pressure (total engine friction divided by displaced cylinder volume). This simple
method is correct in aggregate but does not take into account the effect of engine
speed on efficiency. However, over the normal engine speed range, this
assumption is adequate for predicting engine efficiency. The brake or useable
engine output is obtained from the relation:
bmep = imep - fmep
where bmep is the brake mean effective pressure (work produced per engine cycle
divided by displaced volume). The indicated mean effective pressure is obtained
from the indicated efficiency:
imep = li(mfQHV/Vd)
where the mf is the fuel mass per cycle, QHV is the lower heating value of the fuel,
and Vd is the total cylinder displaced volume.
Thus, the brake mean effective pressure used to determine engine torque (by
scaling with displaced volume) is obtained from the indicated performance, offset
by the friction of the engine. As a consequence, the brake efficiency of the engine
varies appropriately with engine load. Values of 'g =0.38 and fmep = 165 kPa
are used for current gasoline engines, and 7i = 0.48 and fmep = 180 kPa for
current diesels. Based on projected technological improvements, the indicated
efficiency is assumed to increase by 7.5% to ry = 0.41 for gasoline engines and
i = 0.52 for diesels for the year 2020. Meanwhile, engine friction is expected to
decrease by 25% to an fmep value of 124 kPa for gasoline engines and by 15% to
an fmep of 153 kPa for diesel engines.
4.2.2 Current Average Passenger Car
As noted in footnote c, a separate Energy Laboratory compilation study was performed
on 1996 passenger cars to determine the median vehicle based on price, mass, and fuel
consumption, and to calculate the average corresponding numbers for vehicle an fuel
consumption characteristics. The results show that the median vehicle is a mid-sized
passenger sedan with averages of: base price US$ 18,124, base mass 1333 kg, and fuel
consumption of 10.94 L/100km city and 7.90 L/100km highway. These characteristics
closely match the selected current vehicle used in this study.
4.3 Battery Electric
Adequate data are available to quantify the efficiency of pure electric vehicles, although
its history is brief and uneven, based on the extensive development but poor sales record
of recent pure electric vehicles produced. In the model, assumptions for motor and
battery improvements were made to estimate the performance of a future EV.
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18/4
4.3.1 Variables and Assumptions
Motor Torque Curve: Since electric motors have been in service for many
applications and have been tuned to optimize performance, a motor peak torque
and power curve based on today's electric motor can be used for the future as
well, as shown in Figure 9. For automotive purposes, the most popular choice is
an AC induction electric motor.
Characteristics for a 60 kW Electric Motor
240
80
200
?
160
-65
-50
4)120 0
-
-
-35
80 --
40
-2
-+-
-in-
0
Maximum Torque5
Maximum Power
2000
4000
6000
8000
10000
motor speed (rpm)
Figure 4.7: Torque and power characteristics for a 60 kW motor
A motor efficiency map (10x2 1 array) based on motor speed and torque output is
used to model motor efficiency, while the power inverter is assumed to have a
constant efficiency of 94%. Together with the modeled single gear ratio
transmission loss, the total electric motor system efficiency is about 80% over the
combined driving cycle. An additional 15% loss is added in turn-around operation
when the motor is used in regenerative braking to convert mechanical work to
electricity.
Battery Characteristic: Although other technologies are being developed, nickel
metal hydride (NiMH) batteries are the technology of choice for automotive
applications today: They have a specific energy of about 70 Wh/kg and a specific
power of about 150 W/kg"1 . For the year 2020, it is assumed that battery
performance will improve, especially the specific energy, and that battery
performance will be close to meeting the Advanced Battery Consortium's (ABC)
commercial goals of 150 Wh/kg and 300 W/kg1 . These commercial goals are
judged to be the battery performance required to produce acceptable EV
performance. Although NiMH cannot reach this potential, another technology
AuYeung
19/46
such as the lithium-ion battery, may; its specific energy is significantly higher
than that of the NiMH battery technology.
The specific energy assumption has a major impact on EV range and thus appeal,
as will be discussed later in section 5.3. Batteries are not designed to be fully
discharged, which would shortened their lifetime and decrease their capacity.
Also, tipping off the battery at high state of charge is not efficient given the
internal resistance of the batteries. Hence, cycled battery applications tend to
operate usually within the 20-80% SOC. This preferred range would further
decrease the EV range.
4.3.2 Interior Space and Energy Storage Capability
For the pure electric vehicle, battery performance density constraints are of great concern.
In addition to providing the power needed for peak motor power, extra batteries may be
added to increase the energy storage capacity and hence extend vehicle range. However,
extra batteries also add to the vehicle mass and thus require increased motor power,
additional structural support, and more batteries to maintain performance, generating an
undesirable compounding effect. Given this constraint, the battery pack is selected based
only on its power capacity. Also, as mentioned previously, the battery volume must also
be considered because of its possible intrusion into the interior space
4.4 Gasoline/Diesel Electric Hybrid
Data are becoming available for ICE-electric hybrid vehicles, especially for gasoline
hybrids with two limited production versions already in the market. With several
different types of feasible hybrid configurations, and different drivetrain arrangement
within each configuration, the Toyota Prius version of parallel, duel-mode, CVT
configuration was selected and slightly modified for the model.
4.4.1 Variables and Assumptions
Hybrid Configuration: Starting with the most basic distinguishing characteristic,
there are series and parallel hybrids. A series hybrid drives the wheels only
through the electric motor with the combustion engine generating electricity,
whereas a parallel hybrid system powers the wheels directly with both the
combustion engine and electric motor.
Within the parallel hybrid family, there is a further separation between dual-mode
and power-assist, and between road-coupled and wheel-coupled configurations. A
duel-mode drivetrain allows vehicle operation with just the engine, or just the
motor, or with both, whereas a power-assist drivetrain always draws primary
power out of the engine with the electric motor serving only to supplement high
loads. Meanwhile, a road-coupled drivetrain has the two power sources,
unconnected, driving different wheels, whereas a wheel-coupled drivetrain
combines the engine and motor before transferring power to the wheels.
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And within the parallel, dual-mode, wheel-coupled family, the electric motor can
contribute power before or after the geared transmission for the combustion
engine. The Toyota Prius uses a planetary gear setup to couple the engine and the
motor prior to the continuously variable transmission. In our study, the motor
power bypasses the combustion engine/CVT combination, and drives the wheels
directly through a single-speed gear ratio reduction for internal consistency with
the pure electric drive vehicles and for improved efficiency.
Power Logic Control: Controlling the power balance between the combustion
engine and electric motor is a complex task dependent on many factors, such as
driver requirements, power demand, vehicle speed, and battery state of charge.
Many options exist and could be very sophisticated. For the Prius, the power
availability is as shown in Figure 10. It is important to note the useful hybrid
advantage of higher torque at lower engine speeds for the same peak power.
Prius Power Curve Comparison
80
70
60
50
40
0
9. 30
20
-- o- Standard Gasoline
Gasoline Hybrid
-a-
10
-
-_
---
0
0
1000
2000
3000
4000
Engine Contribution
Motor Contribution
5000
6000
Engine Speed (rpm)
Figure 10: Toyota Prius power curve
For the simulation, a simplified control model is used. During low power
situations, only the electric motor is in operation, thus eliminating engine idling
and the less efficient and more polluting modes of operation for combustion
engines. Above a preset threshold, the vehicle will be driven only by the
combustion engine, except at the higher loads, such as during hard acceleration or
hill climbing, when the electric motor serves as a load-leveler and provides the
necessary additional power to add to the engine's maximum output.
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21/46
4.4.2 Engine/BatterySize Matching
For hybrid systems, it is the batteries specific power that is critical, since discharged
batteries can be recharged during ICE operation. The power density chosen for this report
seems feasible for 2020, given the available battery types today.
While all technologies are held to the same peak power to mass ratio, hybrid technologies
have the extra factor in balancing power contribution between the engine and the motor.
Having performed a series of varying power combinations, as shown in Figure 11, we
find a difference in energy consumption of less than 10 %, after taking into account the
battery state of charge and summing it with the fuel consumption to acquire an equivalent
total energy use, noting that the lighter the vehicle (i.e. more engine dependence), the less
energy consuming. However, arguments for more engine or more motor power must be
carefully weighed. On one hand, a larger engine means smaller battery/motor mass and
better highway operation, when the ICE is more efficient; on the other hand, a larger
motor means more effective regenerative braking energy capture and better dual-mode
operation, when the electric motor is preferred in a city setting. In the end, a 30kW motor
is chosen for the advanced ICE parallel hybrids.
2020
2020
2020
2020
2020
2020
baseline advanced advanced advanced advanced advanced
SI ICE
SI ICE
SI Hybrid SI Hybrid SI Hybrid SI Hybrid
gasoline gasoline gasoline gasoline gasoline gasoline
CVT
CVT
CVT
CVT
auto-clutch auto-clutch
Date
Technology
Propulsion System
Fuel
Transmission
VARIABLE
Body & Chassis Mass
Propulsion System Mass
Battery System Mass
Fuel Mass
Occupant Mass
Total Mass
units
kg
kg
kg
kg
kg
kg
864
226
12
23
110
1235
772
216
12
19
110
1129
804
206
182
14
110
1316
794
208
140
14.0
110
1266
783
209
97
14
110
1213
772
210
55
14
110
1161
Power:Weight Ratio
Engine Displacement
Max Engine Power
Max Motor Power
Hybrid Threshold
Wikg
cm3
kW
kW
kW
75.0
1790
92.7
75.0
1635
84.6
75.0
1000
44.2
54.5
4.0
75.0
1200
53.0
41.9
4.0
75.0
1400
61.8
29.2
3.5
75.0
1600
70.7
16.4
1.5
Fuel Energy Use
Battery Status
Combined Energy Use
Tank-to-Wheel Efficiency
MJ/km
MJ/km
MJ/km
%
1.794
1.575
1.794
18.8%
1.575
18.3%
1.028
0.017
1.101
30.1%
1.010
0.014
1.071
29.9%
0.987
0.008
1.022
30.3%
1.108
-0.031
0.970
30.7%
Fuel Energy Use
Battery Status
sp Combined Energy Use
Tank-to-Wheel Efficiency
MJ/km
MJ/km
MJ/km
%
1.339
1.126
1.339
21.1%
1.126
20.0%
0.789
0.038
0.957
25.7%
0.795
0.033
0.939
25.6%
0.818
0.026
0.930
25.2%
0.921
0.003
0.933
24.6%
1,589
4.93
47.7
31.1
1.373
4.26
55.2
26.9
1.036
3.22
73.1
21.2
1.012
3.14
74.9
20.7
0.980
3.04
77.3
20.1
0.954
C
1
RESULTS
)
MJ/km
EquIVflntEngy U.
Gasoline Eq. Consumption L/100km
mpg
Gasoline Eq. Economy
g C/km
Cycle Carbon Emission
2.96
79.4
19.6
Figure 11: Hybrid power configuration comparison
AuYeung
22/46
It is also important to note that the power-assist variant, with the large engine and small
motor, is noticeably more efficient than its advanced ICE counterpart, despite nearly
identical mass and engine specifications. This difference can be attributed to both the
hybrid configuration and the continuously variable transmission. Because of the hybrid
mode, the combustion engine does not idle or operate below 1.5 kW. In addition, the
motor allows for modest regenerative braking, recovering some of the energy that would
otherwise be lost to heat. The CVT also improves the operating conditions by using highefficiency regions of the engine, thus reducing energy consumption. This variant, similar
to the Honda Insight 3 , is the cheapest, lightest, and easiest to manufacture of the hybrids.
4.5 Fuel Cell Electric Hybrid
Data exist only for prototype fuel cell vehicles, and many details about component
performance are unavailable. Also, significant fuel cell system technology improvements
are occurring in stack size and weight for a given power, fuel storage methods, reformer
performance, and cost. Modeling future production fuel cell systems that currently exist
only in prototype form is speculative and uncertain, although overall system component
efficiency numbers can be plausibly estimated.
4.5.1 Variables and Assumptions
Date
Technology
Propulsion System
Fuel
Transmission
battery
VARABE
VARIABLE
Body &Chassis Mass
Propulsion System Mass
Battery System Mass
Fuel Mass
Occupant Mass
Total Mass
2020
2020_
advanced advanced
FC Hybrid Fuel Cell
hydrogen hydrogen
direct
direct
none
opnsc
units
kg
kg
kg
kg
kg
kg
784
365
49
3.5
110
1312
783
411
0
4.0
110
1308
W/kg
kW
kW
75.0
98.4
83.6
75.0
98.1
98.1
RESULTS
Fuel Energy Use
Battery Status
Combined Energy Use
Range (fuel only)
Tank-to-Wheel Efficiency
MJ/km
MJ/km
MJ/km
km
%
0.740
-0.009
0.725
569
45.1%
0.929
Fuel Energy Use
Battery Status
Combined Energy Use
t Range (fuel only)
Tank-to-Wheel Efficiency
MJ/km
MJ/km
MJ/km
km
%
0.589
0.012
0.608
715
40.3%
Power:Weight Ratio
Max Motor Power
a- Peak Stack Power
0
MJ/km
Equivalent Energy Use
Gasoline Eq. Consumption L/100km
E Gasoline Eq. Economy
mpg
0
g C/km
Cycle Carbon Emission
0.673
2.09
112.6
0.0
0.929
518
35.2%
0.648
0.648
742
37.7%
0.02
2.49
94.4
0.0
Figure 12: Hydrogen fuel cell hybridization
AuYeung
Hybrid Configuration: In contrast to the
combustion engine hybrid, the fuel cell
battery hybrid operate on a pure electric
drivetrain, with the fuel cell generating
electricity that powers the electric motor and
accessories, recharges the batteries, or both.
A study at U.C. Davis14 demonstrates that
hybridization of fuel cell vehicles helps
conserve fuel, a savings of 16 % from the
calculations using the model in this study, as
shown in Figure 12. Hybridization is also
preferred and may be necessary for reformer
fuel cell systems to eliminate the lag time of
reformer warm-up and response to driver
demand. The power logic control operates in
a similar manner to that of the combustion
hybrid.
Fuel Cell Power Curve: The fuel cell
system efficiency is based on modeling by
Directed Technologies14. First, the power to
efficiency curve is scaled to the stack size
and to yield the gross power output. Then,
15% of the generated power is diverted to
run the needed fuel cell systems, as shown in
Figure 13 for a 60 kW stack,.
23/46
An additional fuel cell system loss is taken into account for reformer vehicles,
where reduced hydrogen flow concentration results in poorer stack performance
and compromised hydrogen utilization. According to Thomas et al1, the methanol
reformer generates a stream with 75% hydrogen, with a 10% reduction in fuel cell
power; meanwhile, the gasoline reformer generates a stream with 40% hydrogen,
with a 21.5% reduction in fuel cell power. Because of the open flow of the input
stream, both fuel cells have a hydrogen utilization rate of 85%. All numbers from
Directed Technologies are taken as an average of their best and probable cases.
Efficiency for a 60 kW Fuel Cell Stack
70%
7_
50%
40%
0
10
40
30
20
Stack Net Power Output (kW)
50
60
Figure 13: Fuel cell efficiency for a 60 kW stack
4.5.2 Reformer Properties
On-board reformer technologies are not well-developed and are the center of much
research attention, making predictions twenty years ahead difficult. For the simulation, a
15
lumped reformer efficiency is used based on the results from Directed Technologies's
Again, the average of the best and probable cases is used: 82.25% for the methanol steam
reformer and 72.5% for the gasoline partial oxidation reformer. It is assumed that the
batteries or a hydrogen reservoir will compensate for the lag time in power response.
5.0 Vehicle Simulation Results
Based on the above component details and assumptions, the vehicle simulations were
performed, with the results reported in this section. First, we show a direct comparison of
the vehicle-cycle fuel consumption and carbon emission among advanced technologies
selected. Then, we step back to simulations used to verify the validity of the calculations
by simulating existing vehicles to see how our results compare with available data.
AuYeung
24/46
Sensitivity analyses on battery performance and vehicle loading were also completed to
demonstrate what effect more conservative batteries and greater passenger/cargo load
would have on vehicle fuel consumption. Finally, price table comparing the different
technologies is presented.
5.1 Vehicle System Comparison
Figure 14 summarizes the major component input variables, and component and vehicle
results from the vehicle simulation calculations. The US FTP urban (city) and highway
driving cycles were used; ten different vehicle and propulsion systems were examined.
The first column (on the left) in Table 4.3 is a current (1996) average passenger car (note
again that the EPA empirical factor of 0.90 for city and 0.78 for highway are not used for
the results); the second column is the evolving baseline average car projected out to 2020.
The advanced technology vehicles (in 2020) are then arranged in four groups: internal
combustion engine vehicles, internal combustion engine/battery hybrids, fuel cell
hybrids, and electric vehicle. (Note that outlet charging is not included for the battery
electric vehicle total energy consumption.) All these advanced technology vehicles have
reduced vehicle resistances (mass, aerodynamics drag, tire resistance) compared with the
2020 baseline vehicle. Figure 15 lists the descriptions and assumptions that go with each
line item in the summary table.
The results at the bottom of Figure 14 show energy use, fuel consumption/economy,
range, overall vehicle energy efficiency (tank to wheel) for the urban and highway
driving cycles, and for the standard 55% urban 45% highway combined energy/fuel
consumption average, and CO 2 emissions on grams Carbon per average vehicle km
traveled. Combined fuel economy and consumption are expressed in gasoline equivalent
of the energy used. The calculated ranges of each of these vehicles are closely
comparable (above 600 km) except for the EV, which depends strongly on the assumed
battery characteristics. Vehicle performance is held approximately constant with a
maximum power:weight ratio of 75 W/kg.
Note that the numerical values in the summary table, which are given to several
significant figures to match with the assumptions made and input variables chosen, do not
have that level of precision. However, predictions for 20 years into the future obviously
depend strongly on the assumptions and input variables and are unlikely to be better than
± 10-15% in a relative technology to technology comparison sense. Note that all columns
show a substantial reduction in energy consumption and CO 2 emissions as compared to
the baseline vehicle, because of the compounding effects of reducing vehicle resistances
and the corresponding maximum propulsion system power, and of improving the
propulsion system efficiency (both power unit and transmission).
AuYeung
25/46
2020
2020
2020
2020
2020
2020
2020
2020
2020
1996
baseline advanced advanced advanced advanced advanced advanced advanced advanced
current
SI Hybrid Cl Hybrid FC Hybrid FC Hybrid FC Hybrid Electric
Cl ICE
SI ICE
SI ICE
SI ICE
gasoline methanol hydrogen electricity
diesel
gasoline
diesel
gasoline
gasoline gasoline
direct
direct
direct
direct
CVT
CVT
auto-dutch auto-dutch auto-clutch
auto
Date
Technology
Propulsion System
Fuel
Transmission
;
VARIABLE
Body & Chassis Mass
Propulsion System Mass
Battery Mass
Fuel Mass
Occupant Mass
Total Mass
units
kg
kg
kg
kg
kg
kg
Rolling Resistance Coeff.
Drag Coefficient
Frontal Area
Auxiliary Power
Power:Weight Ratio
--
---
m2
W
W/kg
Engine Displacement
Transmission Efficiency
Indicated Efficiency
Frictional MEPressure
Max Engine Power
cm3
---
Hybrid Threshold
0 Gear Efficiency
Z
Electric Motor Efficiency
Max Motor Power
kW
H2 Flow Concentration
o Fuel Cell System Efficiency
& Reformer &Utilization Eff.
u- Peak Stack Power
%
C
U
---
kPa
kW
930
340
12
40
110
1432
864
226
12
23
110
1235
772
216
12
19
110
1129
778
269
12
17
110
1186
785
209
100
14
110
1218
794
248
100
12
110
1264
822
483
56
23
110
1494
803
401
53
36
110
1403
784
365
49
3.5
110
1312
782
85
326
0
110
1303
0.009
0.33
2.0
400
76.6
0.008
0.27
1.8
400
75.0
0.006
0.22
1.8
400
75.0
0.006
0.22
1.8
400
75.0
0.006
0.22
1.8
400
75.0
0.006
0.22
1.8
400
75.0
0.006
0.22
1.8
400
75.0
0.006
0.22
1.8
400
75.0
0.006
0.22
1.8
400
75.0
0.0060
0.22
1.8
400
75.0
2500
0.7-0.8
0.38
165
109.7
1790
0.88
0.41
124
1635
0.88
0.41
124
92.7
84.6
1922
0.88
0.51
154
88.9
1390
0.88
0.41
124
61.4
1396
0.88
0.51
153
64.8
3.5
0.80
0.80
30.0
4.0
0.79
0.80
30.0
5.0
0.93
0.80
112.0
5.0
0.93
0.80
105.2
5.0
0.93
0.80
98.4
0.95
0.82
97.7
40%
0.42
0.62
95.2
75%
0.48
0.70
89.4
100%
0.53
---
kW
---
--kW
Lower Heating Value
u. Fuel Density
MJ/kg
kg/L
? Battery Discharge Efficiency
: Specific Energy
w Specific Power
Wh/kg
W/kg
43.7
0.737
43.7
0.737
43.7
0.737
41.7
0.856
---
83.6
43.7
0.737
41.7
0.856
43.7
0.737
20.1
0.792
120.2
0.95
150
300
0.95
150
300
0.95
150
300
0.95
150
300
0.95
150
300
0.95
150
300
0.989
0.008
1.024
3.07
76.6
619
30.3%
0.848
0.003
0.857
2.38
99.0
590
37.4%
1.733
-0.016
1.677
5.38
43.7
580
21.9%
1.268
-0.009
1.235
7.97
29.5
571
28.1%
0.740
-0.009
0.725
0.396
0.396
569
45.1%
445
89.4%
0.710
0.022
0.792
1.99
118.2
705
30.3%
1.345
0.003
1.355
4.18
56.3
747
19.5%
0.994
0.007
1.017
6.24
37.7
728
25.0%
0.589
0.012
0.608
0.320
0.320
715
40.3%
550
77.1%
0.828
2.57
91.5
17.3
1.532
4.76
49.4
30.0
1.137
3.53
66.6
21.2
0.673
2.09
112.6
0.0
0.362
RESULTS
:
MJ/km
MJ/km
MJ/km
Fuel Energy Use
Battery Status
Combined Energy Use
Fuel Consumption
Fuel Economy
Range (fuel only)
Tank-to-Wheel Efficiency
U/100km
Fuel Energy Use
Battery Status
Combined Energy Use
Fuel Consumption
Fuel Economy
Range (fuel only)
Tank-to-Wheel Efficiency
MJ/km
MJ/km
MJ/km
L/100km
mpg
km
%
Equivalent Energy Use
Gasoline Eq. Consumption
Gasoline Eq. Economy
Cycle Carbon Emission
MJ/km
LJ100km
mpg
gC/km
mpg
km
%
3.071
1.794
1.575
1.413
3.071
9.53
24.7
569
13.5%
1.794
5.57
42.2
560
18.8%
1.575
4.89
48.1
527
18.3%
1.413
3.96
59.4
502
21.2%
2.083
1.339
1.126
0.979
2.083
6.47
36.4
839
17.6%
1.339
4.16
56.6
751
21.1%
1.126
3.50
67.3
738
20.0%
0.979
2.74
85.8
724
23.6%
0.818
0.026
0.930
2.54
92.6
748
25.3%
2.626
1.589
4.93
47.7
31.1
1373
4.26
55.2
26.9
1.218
3.78
62.2
25.4
0.982
3.05
77.2
19.2
8.15
28.8
51.4
Figure 14: Summary results for test vehicles
AuYeung
26/46
VARIABLE
Body & Chassis Mass
Propulsion System Mass
Battery Mass
Fuel Mass
Occupant Mass
Total Mass
units
kg
kg
kg
kg
kg
kg
see vehicle mass distribution
Rolling Resistance Coeff.
Drag Coefficient
Frontal Area
> Auxiliary Power
Power:Weight Ratio
.--
assumed constant, = 0.009 for current 0.008 for evolutionary, 0.006 for advanced.
assumed constant, = 0.33 for current, 0.27 for evolutionary, 0.22 for advanced.
assumed constant, =2.0 for current, 1.8 for future.
assumed constant, = 400 W during vehicle operation.
maximum totl power available / total mass, held constant at 0.75 W/kg.
see vehicle mass distribution
see vehicle mass distribution
except for electric vehicle, fuel is scaled for -6001n range.
assumed 1.5 occupants with cargo =110 kg.
sum of all masses on board
---
m2
W
W/kg
Engine Displacement
Transmission Efficiency
Indicated Efficiency
W Frictional MEPressure
Max Engine Power
cm3
kPa
kW
chosen according to engine power desired.
assumed constant, = 0.7 for current city automatic, 0.8 for current highway automatic, 0.88 for automatics clutch and continuously variable.
assumed constant, = 0.38 for current gasoline, 0.41 for future gasoline, and 0.51 for future diesel.
assumed constant, =165 kPa for current gasoline, = 124 kPa for future gasoline, and 153 kPa for future diesel.
maximum power from combustion engine.
Hybrid Threshold
Gear Efficiency
Electric Motor Efficiency
Max Motor Power
kW
kW
--kW
power below which hybrids are only driven with batteries.
modeling result, dependent on load and speed.
modeling result, dependent on load and speed.
maximum power from electric motor.
H2 Flow Concentration
%
0 Fuel Cell System Efficiency
Reformer & Utilization Eff.
IL Peak Stack Power
---
---
hydrogen concentration available to fuel call; affects stack efficiency.
modeling result based on energy produced by fuel call for road use / energy in hydrogen into fuel cell.
---
energy in hydrogen consumable by fuel cell / energy stored in fuel for conversion.
maximum power from fuel cell stack, contributing 85% of fuel cell hybrid available power.
---
kW
Lower Heating Value
u. Fuel Density
MJ/kg constants; usual to define ICE efficiency with lower heating value.
kq/L constants.
Z Battery Discharge Efficiency
Sp
2 Specific Energy
Specific Power
Wh/kg
W/kg
RESULTS
Fuel Energy Use
Battery Status
Combined Energy Use
Fuel Consumption
Fuel Economy
Range (fuel only)
Tank-to-Wheel Efficiency
MJ/km
MJ/km
MJ/km
LU100km
mpg
km
%
modeling result
modeling result.
MJ/km
MJ/km
modeling result.
modeling result.
Fuel Energy Use
Battery Status
Combined Energy Use
Fuel Consumption
Fuel Economy
Range (fuel only)
Tank-to-Wheel Efficiency
Equivalent Energy Use
---
assumed constant, = 95%.
US Advance Battery Consortium commercial goal =150 Wh/kg.
US Advance Battery Consortium commercial goal = 300 W/kg.
vehicle energy use, specific to city driving cycle; for hybrids, battery use is adjusted by a factor to take into account final battery SOC.
consumption of fuel only.
equivalent economy of fuel only.
driving range of vehicle based on fuel on board and the city driving cycle, (excludes battery charge depletion at low speeds).
energy supplied to wheels / total energy use: note regenerated energy not included.
MJ/km vehicle energy use, specific to highway driving cycle; for hybrids, battery use is adjusted by a factor to take into account final battery SOc.
L/100km
mpg
km
%
MJ/km
consumption of fuel only.
equivalent economy of fuel only.
driving range of vehicle based on fuel on board and the highway driving cycle, (excludes battery charge depletion at low speeds).
energy supplied to wheels / total energy use; not regenerated energy not included.
combined vehicle cycle energy use, with 55% city and 45% highway operation.
Gasoline Eq. Consumption
L100km total energy use converted to equilvalent gasoline fuel consumption.
Gasoline Eq. Economy
Cycle Carbon Emission
total energy use converted to equilvalent gasoline fuel economy.
mpg
q C /km carbon emitted during combined vehicle cycle.
Figure 15: Brief comments on variables listed
5.2 Verification with Available Data
Validation studies of the simulation were tested on current production and prototype
vehicles, including the 1996 Toyota Camry (4-cylinder manual and auto, and 6-cylinder
automatic) 16, the 1990 Audi 100 turbo diesel (5-cylinder manual)' 7 , the Toyota Prius (4cylinder CVT hybrid)18 , the Ford P2000 prototype hydrogen fuel cell vehicle' 9 , and the
GM EVI (NiMH batteries) limited production electric vehicle 20 , as shown in Figure 16.
AuYeung
27/4.6
VARIABLE
kg
kg
kg
kg
kg
Total Mass
kg
Rolling Resistance Coeff.
Drag Coefficient
Frontal Area
> Auxiliary Power
Power:Weight Ratio
M
units
Body &Chassis Mass
Propulsion System Mass
Battery Mass
Fuel Mass
Occupant Mass
---
m2
W
W/kg
cm3
Hybrid Threshold
Gear Efficiency
Electric Motor Efficiency
Max Motor Power
kW
kW
H2 Flow Concentration
IR Reformer &Utilization Eff.
LL Peak Stack Power
vehicle mass distribution
vehicle mass distribution
see vehicle mass distribution
except for electric vehicle, fuel is scaled for -OOkmi
assumed 1.5 occupants with cargo =110 kg.
sum of all messes on board
see
---
Engine Displacement
Transmission Efficiency
Indicated Efficiency
Frictional MEPressure
Max Engine Power
0 Fuel Cell System Efficiency
see
range.
assumed constant, = 0.009 for current 0.008 for evolutionary, 0.006 for advanced.
assumed constant, = 0.33 for current, 0.27 for evolutionary, 0.22 for advanced.
assumed constant, = 2.0 for current, 1.8 for future.
assumed constant, = 400 W during vehicle operation.
maximum total power available / total mass, held constant at 0.75 W/kg.
chosen according to engine power desired.
assumed constant, = 0.7 for current city automatic, 0.8 for current highway automatic, 0.88 for automatice clutch and continuously variable.
assumed constant = 0.38 for current gasoline, 0.41 for future gasoline, and 0.51 for future diesel.
assumed constant, = 165 kP for current gasoline, = 124 kPa for future gasoline, and 153 kPa for future diesel.
maximum power from combustion engine.
---
.-.
kPa
kW
power below which hybrids are only driven with batteries.
modeling result, dependent on load and speed.
modeling result, dependent on loed and speed.
maximum power from electric motor.
---
kW
hydrogen concentration available to fuel cell; affects stack efficiency.
modeling result based on energy produced by fuel cell for road use / energy in hydrogen into fuel cell.
energy inhydrogen consumable by fuel cell / energy stored in fuel for conversion.
maximum power from fuel cell stack contributing 85% of fuel cell hybrid avallable power.
%
-----
kW
-6 Lower Heating Value
U Fuel Density
MJ/kg
kq/L
t Battery Discharge Efficiency
Specific Energy
Specific Power
Wh/kg US Advance Battery Consortium commercial goal = 160 Wh/kg.
W/kg US Advance Battery Consortium commercial goal = 300 W/kg.
RESULTS
Fuel Energy Use
Battery Status
Combined Energy Use
Fuel Consumption
Fuel Economy
Range (fuel only)
Tank-to-Wheel Efficiency
---
constants; usual to define ICE efficiency with lower heating value.
constants.
assumed constant, = 95%.
MJ/km
MJ/km
MJ/km
modeling result.
modeling result.
vehicle energy use, specific to city driving cycle; for hybrids, battery use is adjusted by a factor to take into account final battery SOC.
L/100km consumption of fuel only.
mpg equivalent economy of fuel only.
km
driving range of vehicle based on fuel on board and the city driving cycle, (excludes battery charge depletion at low speeds).
%
energy supplied to wheels / total energy use: note regenerated energy not included.
Fuel Energy Use
MJ/km
modeling result.
Battery Status
MJ/km
modeling result.
MJ/km
vehicle energy use, specific to highway driving cycle; for hybrids, battery use is adjusted by a factor to take into account final battery SOC.
Combined Energy Use
Fuel Consumption
F Fuel Economy
Range (fuel only)
Tank-to-Wheel Efficiency
Equivalent Energy Use
Gasoline Eq. Consumption
LU100km consumption of fuel only.
equivalent economy of fuel only.
driving range of vehicle based on fuel on board and the highway driving cycle, (excludes battery charge depletion at low speeds).
energy supplied to wheels / total energy use; not regenerated energy not included.
mpg
km
%
MJ/km
combined vehicle cycle energy use, with 55% city and 45% highway operation.
1/100km total energy use converted to equilvalent gasoline fuel consumption.
total energy use converted to equilvalent gasoline fuel economy.
Gasoline Eq. Economy
mpg
Cycle Carbon Emission
q C /km
carbon emitted during combined vehicle cycle.
Figure 15: Brief comments on variables listed
5.2 Verification with Available Data
Validation studies of the simulation were tested on current production and prototype
vehicles, including the 1996 Toyota Camry (4-cylinder manual and auto, and 6-cylinder
automatic) 16, the 1990 Audi 100 turbo diesel (5-cylinder manual)' 7 , the Toyota Prius (4cylinder CVT hybrid) 8 , the Ford P2000 prototype hydrogen fuel cell vehicle' 9 , and the
GM EVI (NiMH batteries) limited production electric vehicle2 0 , as shown in Figure 16.
AuYeung
27/46
consumption depends heavily on environmental temperature, accessory loading, and
possibly charging efficiency. The Partnership for a New Generation of Vehicles (PNGV)
has also produced promising prototypes that include diesel hybrids and fuel cell vehicles
that have achieved dramatically low energy consumption.
numbers in mpg gasoline equivalent Published/Reported Unadjusted/Actual
Simulation Result
MODEL
power unit
trans.
City
Highway
City
Highway
City
Highway
Toyota Camry 4-cyl gas
manual
23
31
25
39
30.1
40.8
Toyota Camry 4-cyl gas
auto
21
27
23
35
25.3
37.3
Toyota Camry 6-cyl gas
auto
20
29
23
37
23.7
33.5
Audi 100
5-cyl dies
manual
33.1
41-56
37
40.0
55.1
Toyota Prius gas hybrid
CVT
lower 50's lower 40's
45.1
46.3
Ford P2000 hyd fuel cell
direct
56
80
57.9
72.1
GM EV1
battery elec
direct 1
99.6
112.9
166.0
200.1
Percent Difference
City
Highway
20%
5%
10%
7%
3%
-9%
9%
<10%
<15%
<5%
3%
-10%
67%
77%
Figure 17: Comparison of fuel economy results with existing data
5.3 Battery Projection
Battery technology is a potential barrier to the hybrids' success at reducing their energy
consumption and will also determine the fate of the pure battery electric vehicle.
Realizing the USABC commercial goal of 150 Wh/kg and 300 W/kg will enable the
energy reductions as listed in Figure 14. However, if this goal is not reached, then the
vehicles relying on electric drive may be affected.
To compare our results with calculations using a more conservative battery technology,
we chose the USABC short-term desired goal of 100 Wh/kg and 200 W/kg, which some
marketable Lithium ion batteries are rapidly approaching today. This more conservative
battery performance is then used on the vehicles with the highest carbon reduction
potential, the diesel hybrid and the hydrogen fuel cell hybrid, which increased their
overall mass because a heavier battery pack, stronger motor, and greater structural
support (with compounding effects) are needed to maintain the constant power-to-mass
ratio. The subsequent increase in energy consumption of 4 % for the diesel and 3 % for
the hydrogen fuel cell, as shown in Table 18, reflect their respective hybridized
dependence on the batteries, with the ICE hybrid relying more on battery power than the
FC hybrid. Surprisingly, the difference in performance is not catastrophic.
However, for the battery electric vehicle, the effects are more noticeable. Already
deficient in range because of the low energy density of batteries, a simple swap to the
more conservative batteries without changing the mass created a significant drop in
power and range, also shown in Figure 18. And by reestablishing the power-to-mass
ratio, the vehicle increase in mass by 34 % and in fuel consumption by 26.5 %, making
the EV even less attractive.
AuYeung
29/416
2020
Date
battery
VARIABLE
Body & Chassis Mass
2020
2020
2020
2020
2020
2020
2020
2020
baseline advanced advanced advanced advanced advanced advanced advanced advanced
Electric
Electric
Cl Hybrid Cl Hybrid FC Hybrid FC Hybrid Electric
SI ICE
Si ICE
diesel
hydrogen hydrogen electricity electricity electricity
diesel
gasoline gasoline
direct
direct
direct
direct
CVT
direct
CVT
auto-clutch auto-clutch
Technology
Propulsion System
Fuel
Transmission
nra
opfimisti
convennal
optinstk
conventonal
optimi&
repiscement convenonal
units
kg
864
772
794
810
784
798
782
782
874
kg
kg
kg
kg
kg
226
12
23
110
1235
216
12
19
110
1129
248
100
12
110
1264
258
150
13
110
1341
365
49
3.5
110
1312
389
78
4.0
110
1379
85
326
0
110
1303
85
326
0
110
1303
107
655
0
110
1746
Power:Weight Ratio
Engine Displacement
Max Engine Power
a- Max Motor Power
W/kg
cm3
kW
kW
75.0
1790
92.7
75,0
1635
84.6
75.0
1396
64.8
30.0
75.0
1522
70.6
30.0
75.0
75.0
75.0
50.0
75.0
97.7
97.7
131.0
Peak Stack Power
kW
Propulsion System Mass
Battery System Mass
Fuel Mass
Occupant Mass
Total Mass
x
Battery Discharge Efficiency
Specific Energy
' Specific Power
RESULTS
Fuel Energy Use
Battery Status
Combined Energy
Fuel Consumption
Fuel Economy
103.4
87.9
Wh/kg
0.95
150
0.95
100
0.95
150
0.95
100
0.95
150
0.95
100
0.95
100
W/kg
300
200
300
200
300
200
200
1.575
0.848
0.891
0.740
0.772
1.794
1.575
0.003
0.857
0.002
0.898
-0.009
0.725
-0.016
0.746
0.396
0.396
0.396
0.396
0.513
0.513
5.57
42.2
4,89
48.1
2.38
99.0
2.50
94.3
-.-
MJ/km
Use
98.4
83.6
1.794
MJ/km
MJ/km
U100km
mpg
Range (fuel only)
km
560
527
590
609
569
623
445
297
460
Tank-to-Wheel Efficiency
%
18.8%
18.3%
37.4%
38.0%
45.1%
45.8%
89.4%
89.4%
89.5%
Fuel Energy Use
MJ/km
1.339
1.126
0.710
0.733
0.589
0.618
Battery Status
Combined Energy Use
MJ/km
MJ/km
1.339
1.126
0.022
0.792
0.023
0.821
0.012
0.608
0.004
0.625
0.320
0.320
0.320
0.320
0.392
0.392
4.16
56.6
751
21.1%
3.50
67.3
1.99
118.2
2.05
114.5
738
20.0%
705
740
715
778
550
366
601
30.3%
30.5%
40.3%
40.3%
77.1%
77.1%
75.4%
1.589
4.93
47.7
31.1
1.373
4.26
55.2
26.9
0.828
2.57
91.5
17.3
0.863
2.68
87.8
18.0
0.673
2.09
112.6
0.0
0.692
2.15
109.5
0.0
0.362
0.362
0.458
Fuel Consumption
3Fuel Economy
U1100km
mpg
Range (fuel only)
km
Tank-to-Wheel Efficiency
%
MJ/km
Equivalent Energy Use
Gasoline Eq. Consumption U100km
mpg
Gasoline Eq. Economy
g C /km
Cycle Carbon Emission
Figure 18: Battery impact on vehicle mass and energy consumption
5.4 Vehicle Load Sensitivity
Analyses for all technologies were performed with a passenger/cargo load of 110 kg; and
to determine the consumption sensitivity to increased load, the vehicles were tested again,
this time with 4 adults at 70 kg each and 15 kg of cargo, totaling 295 kg, as documented
in Figure 19. The advanced vehicles have less mass compared to the conventional or
evolutionary cars, hence a heavier passenger/cargo load would represent a larger fraction
of the total moving mass, affecting the power availability and fuel consumption.
The ICE vehicles show themselves to be more robust with various loading, with a larger
percent mass increase (12.9-16.4 %) but a smaller percent energy consumption increase
(4.4-5.5 %). Meanwhile, the electric drive vehicles, including all the FC models and the
EV, had greater percent consumption increase (7.5-9.0 %) with smaller percent mass
increase (12.4-14.2 %). This trend can be attributed to the nonlinear efficiency of the
AuYeung
30/4-6
ICE, which can generate more power with less additional fuel use, whereas the electric
motor and corresponding power units have more constant power delivery efficiencies.
2020
2020
2020
2020
2020
2020
2020
2020
1996
2020
baseline advanced advanced advanced advanced advanced advanced advanced advanced
current
SI Hybrid Cl Hybrid FC Hybrid FC Hybrid FC Hybrid Electric
Cl ICE
SI ICE
SI ICE
SI ICE
gasoline methanol hydrogen electricity
diesel
gasoline
diesel
gasoline
gasoline
gasoline
direct
direct
direct
direct
CVT
CVT
auto
auto-clutch auto-clutch auto-clutch
Date
Technology
Propulsion System
Fuel
Transmission
VARIABLE
Vehicle Mass
Occupant Mass
Total Mass
units
kg
kg
kg
Power:Welght Ratio
Max Engine Power
Max Motor Power
Peak Stack Power
1322
295
1617
1125
295
1420
1019
295
1314
1076
295
1371
1108
295
1403
1154
295
1449
1384
295
1679
1293
295
1588
1202
295
1497
1193
295
1488
W/kg
kW
kW
kW
67.8
109.7
65.3
92.7
64.4
84.6
65.1
89.2
65.2
61.5
30.0
65.8
65.3
30.0
66.7
66.2
65.8
65.7
112.0
95.2
105.2
89.4
98.4
83.6
97.7
RESULTS
Fuel Energy Use
Battery Status
Combined Energy Use
Fuel Consumption
Fuel Economy
Range (fuel only)
Tank-to-Wheel Efficiency
MJ/km
MJ/km
MJ/km
L100km
mpg
km
%
3.218
1.893
1.669
1.497
3.218
9.99
23.5
543
14.2%
1.893
5.88
40.0
531
20.1%
1.669
5.18
45.4
497
19.6%
1.497
4.19
56.1
474
22.7%
1.122
-0.009
1.081
3.48
67.5
545
32.5%
0.960
-0.016
0.897
2.69
87.5
521
40.2%
1.949
-0.035
1.828
6.05
38.9
516
22.3%
1.415
-0.022
1.339
8.89
26.5
511
28.9%
0.840
-0.026
0.799
0.433
0.433
501
46.0%
406
91.8%
Fuel Energy Use
Battery Status
Combined Energy Use
Fuel Consumption
! Fuel Economy
Range (fuel only)
Tank-to-Wheel Efficiency
MJ/km
MJ/km
MJ/km
LJ100km
mpg
km
%
2.161
1.391
1.178
1.017
2.161
6.71
35.1
809
18.1%
1.391
4.32
54.4
722
21.9%
1.178
3.66
64.3
705
20.8%
1.017
2.85
82.6
697
24.7%
0.880
0.021
0.974
2.73
86.1
696
26.2%
0.758
0.018
0.827
2.12
110.8
660
31.4%
1.449
-0.002
1.441
4.50
52.3
694
19.7%
1.073
0.002
1.078
6.74
34.9
674
25.4%
0.649
0.002
0.653
0.338
0.338
40.5%
520
79.0%
2.742
4.4%
12.9%
8.51
27.6
53.7
1.667
4.9%
15.0%
5.18
45.4
32.6
1.448
5.5%
16.4%
4.50
52.3
28.3
1.281
1.032
0.866
1.854
1.221
0.733
0.391
5.2%
15.6%
3.98
59.1
26.7
5.2%
15.2%
3.21
73.4
20.2
4.5%
14.6%
2.69
87.5
18.1
8.0%
7.5%
13.2%
3.79
62.0
22.8
9.0%
14.1%
2.28
103.4
0.0
7.9%
14.2%
2020
2020
2020
Equivalent Energy Use
% Consumption increase
%Mass Increase
Gasoline Eq. Consumption
Gasoline Eq. Economy
Cycle Carbon Emission
MJ/km
%
%
l/100km
mpg
g C /km
12.4%
5.14
45.8
32.4
648
Figure 19: Consumption sensitivity to increased load
1996
Date
current
SI ICE
gasoline
Technology
Propulsion System
Fuel
auto
Transmission
Gasoline Eq. Consumption
L/100km
normalized over evolutionary
%
Vehicle Cycle C Emission
g C /km
normalized over evolutionary
Vehicle Price
Operating Cost
normalized over evolutionary
8.15
51.4
%
2020
2020
2020
2020
2020
2020
advanced advanced advanced advanced advanced advanced advanced advanced
Cl ICE
SI Hybrid Cl Hybrid FC Hybrid FC Hybrid FC Hybrid Electric
SI ICE
gasoline methanol hydrogen electricity
diesel
gasoline
diesel
gasoline
direct
direct
direct
direct
CVT
CVT
auto-clutch auto-clutch auto-clutch
baseline
SI ICE
gasoline
4.93
4.26
3.78
3.05
2.57
4.76
3.53
2.09
0.00
100%
86%
77%
62%
52%
96%
72%
42%
0%
31.1
26.9
25.4
19.2
17.3
30.0
21.2
0.0
0.0
100%
86%
82%
62%
56%
96%
68%
0%
0%
1997 US$
17200
18000
19400
20500
23300
24300
28200
27500
25500
26100
US$/km
%
0.306
0.304
100%
0.320
108%
0.329
114%
0.363
129%
0.373
135%
0.430
157%
0.417
153%
0.394
142%
0.394
145%
Figure 20: Price summary relative to carbon emission
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5.5 Estimated Retail Price
A detailed vehicle price study was completed by Dr. Andreas Schafer, as documented in
Appendix B, with a summary table relative to the vehicle cycle only gasoline-equivalent
energy consumption and carbon emission, as presented in Figure 20. From the vehicle
cycle, the hydrogen fuel cell and the electric vehicles offer zero-emission options at a
cost, with the next best options being the diesel and gasoline ICE hybrids. These results
suggest that the methanol and gasoline reformer fuel cells, aside from research value,
offer little carbon benefits at a high cost.
6.0 Vehicle Technology Conclusions
The vehicle simulation results presented in Section 5.1 suggest that impressive fuel
economy and CO 2 emissions benefits may be realizable, with the potential range
dependent upon the assumptions made about the component performance characteristics
and their subsequent compounding effect with each other. Before a summary comparing
the numerical results, it is appropriate to restate the intent of these calculations, and to
highlight the key factors of the technologies discussed.
6.1 Study Intentions
The assumptions and results are projections of what potentially practicable vehicle and
propulsion system improvements might produce in terms of reduced average passenger
car energy consumption and CO 2 emissions by about 2020, with other vehicle
performance attributes roughly held at today's levels. Driveability issues such as ease of
start up, driving smoothness, and operation temperature range are assumed to be solvable
for each technology. Transient response for rapid accelerations is expected to be
addressed by sophisticated power control electronics for hybrids and short-term reserve
storage for fuel cell vehicles. Power-related issues such as hill climbing, and load
carrying/pulling capacity are assumed to be satisfactory given the more than adequate
preset power-to-weight ratio for all technologies.
For them to be feasible, the combinations of technologies would need to be in mass
production and so have gone through extensive engineering development prior to 2020,
and would need to have sufficient market appeal to reach the a moderate production
level. The energy consumption numbers calculated in this study represent our estimates
of what could happen to passenger car fuel consumption over the next 20 years, and not
necessarily what we judge will or ought to happen. Barriers and enablers for these
different technologies regarding the potential in the marketplace are discussed in the
larger Energy Laboratory report.
Also, the calculations involve many numerical inputs, resulting in a certain degree of
uncertainty. We have attempted to be as internally consistent with these inputs as is
feasible, but of course, there are still error margins in many of these numbers. The
uncertainties are significantly less where we are extrapolating from the performance of
well established technologies (such as steel chassis and body components, and sparkignition engines). The uncertainties in performance, weight and cost, increase for
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technologies that have come into production relatively recently, but whose ultimate
potential is still being explored (e.g. extensive use of aluminum, small low-emissions
diesel engines, continuously variable transmissions). And the uncertainties become much
greater for new technologies such fuel cells and high performance batteries, where the
performance and cost of current versions of these technologies fall far short of what
would be required for market feasibility. Here we have used literature assessments of the
future development potential, tempered by our own judgments of plausible long-term
technology improvements.
6.2 Technology Highlights
The advanced vehicle bodies with reduced mass raises several safety and handling issues;
safety performance in required government tests must be maintained or surpassed,
possibly by adding extra features to compensate for reduced energy absorption as the
body is crushed. Innovations regarding safety may require extra cost and mass that we
may have not included here.
The internal combustion engine has made a place for itself in history, and will likely stay
for decades to come as the most economic choice for power units. The gasoline engine
remains the most used, most robust, and most well-researched of the ICE's, with the
potential for further improvement in both fuel economy and pollutant reduction.
Meanwhile, the diesel engine is more efficient and is thus more popular for long range
transportation trucks. However, its pollutant emission, especially NOx and small
particulates, may hurt its future given stricter regulations. Innovations in diesel exhaust
treatment, even at the expense of sacrificing efficiency, will prove to be very important,
particularly in Europe, where diesels are used much more extensively. Finally,
compressed natural gas engines are also an area of interest for urban use because of its
cleaner properties. We hope to include CNG and CNG hybrids in upcoming reports.
Hybrid technology holds much promise as the next logical step to maximize the inherent
advantages of the ICE, at higher loads in selective ranges of operation. New production
models are now being tested on market, with many more companies following suit. Their
power control methods and technologies are much more complex than the one simulated
here, which is either-or, or both depending on power requirement. However, much more
can be accomplished with more sophisticated controls, not just increasing mileage, but
also lowering emissions and improving performance. Electromotive, Inc. proposes an
electric assist system that dramatically reduces transient emissions while decreasing fuel
consumption . Different approaches to the hybrid concept will likely be explored by
researchers and competing companies, designs that will take into account the potential
danger of a sustained peak power load discharging the batteries, such as during hill
climbing or prolonged acceleration or top speed
Fuel cell technology is still relatively new to the automotive application, and will require
much research and developing time and money. From our study here, it seems that
reformer technologies are not optimistic in terms of reducing carbon output, while the
direct hydrogen fuel cell, without the reformer losses and weight, seems to be a run-away
winner. However, the lack of a hydrogen infrastructure and the safety issues around
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hydrogen may prove to be substantial barriers to market entry. Furthermore, while mass
was estimated in this study, the propulsion system volume and its direct impact on the
vehicle were not. The extra space that may be needed could translate into a larger or
differently shaped vehicle and increase resistances, indicating that our results are likely
an upper bound for its potential performance. One of the most critical space and mass
issue for the hydrogen fuel cell is the hydrogen storage, with current options being a
standard compressed gas tank and a chemical hydride storage, both of which cannot store
hydrogen more than 5 % of the storage unit mass.
All vehicles with electric drive including the ICE and FC hybrids, and particularly the
electric vehicle, are directly effected by improvements in electrical components such as
more efficient motors, inverters, power electronics, and especially batteries. While we
have chosen the USABC commercial goal to be a feasible target by 2020, we have also
pointed out the battery assumption has drastic effects on vehicle specifications and
performance. Ultra-capacitors are an alternative to electrical energy storage, but its
development is slow and uncertain at this point.
Finally, it is worth mentioning that the EV has the potential to be a total zero-emission
vehicle, if green electricity is used to recharge the batteries. All vehicles with batteries
can charge from a standard outlet, which can be environmentally beneficial if the
electricity source is renewable. They can also bypass the grid and charge directly from
solar arrays, either mounted permanently on the vehicle, unveiled only during parked
situations, or at specially designed parking spaces, thus making the electric drive even
more attractive in terms of consuming sustainable, non-polluting energy, in addition to
less tailpipe emissions in urban areas.
6.3 Vehicle Cycle Summary
In assessing the potential of these different technology combinations, we have ensured
comparability among the vehicles by setting the power-to-mass ratio, travel range, and
general size to a general standard. However, as researchers at Carnegie Mellon argue,
consumers may perceive attribute "bundles" to be more flexible, that is, they may be
value one feature over another for particular applications 23. For example, a consumer may
prefer a small EV with limited range for her daily commute instead of a mid-sized EV
loaded with batteries for increased range she does not need. In reviewing the results of
this study, one has to remember the initial assumptions that derived the conclusions.
Numerically, the results have mathematical uncertainties in addition to real life driving
uncertainties, and should be read with a certain margin of error. Perhaps more effective is
comparing these different vehicle and propulsion system combinations in terms of their
percentage reduction in fuel consumption relative to the evolving baseline vehicle level in
2020, utilizing the internal consistencies in assumptions and calculation methods. It is
also important that the total impact of these various technologies be assessed in the
context of the total fuel supply, vehicle production and recycling, and vehicle use cycle,
summed together to compare the total energy consumption and carbon emission.
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Finally, as explained previously, prior technology assessment literature have usually
underestimated the steady improvement of the baseline or mainstream technology with
time, and overestimated the performance of new technology, often not considering the
more pragmatic, often difficult to quantify, but important attributes (such as start-up time
and refueling ease) crucial to vehicle users. Also, the time required to develop new
automotive technologies to the point where they have market potential, and to design
mass-production feasible versions of these technologies, has consistently been too
optimistic. Our own studies reported here, despite efforts to develop a more balanced
approach, may have these deficiencies too. Our specific summary conclusions on relative
vehicle technology performance and price follows; comparisons of energy consumption
or fuel economy refer to fuel loaded on board the vehicle and not to the total well-towheels cycle:
1.
The projected evolving baseline passenger car improvements, which are likely to
be driven by market pressures and some tightening of regulations, are significant:
15% reduction in vehicle mass, nearly 40% reduction in fuel consumption, and
about 5% price increase, as compared to today's (1996) average car.
2. The more advanced vehicle technology car, with the same improved baseline
gasoline engine and improved transmission, and with further reductions in mass
and resistances, decreases the mass by almost 10 % and fuel consumption by a
further 14 %, relative to the 2020 evolving baseline car, at an additional 8 % price
increase.
3. The gasoline CVT hybrid shows an further reduction of about 30 % compared to
the advanced gasoline ICE vehicle, and about 40 %compared to the evolving car,
but at a price increase of 20 % and 30 % relative to the advanced and evolving
vehicles respectively. Note also that the hybrid has a significant advantage during
the city cycle.
4. The diesel engine provides extra energy advantages at an increased initial cost and
with possible emissions compliance issues. The advanced diesel ICE vehicle is
about 10 % less energy consuming but more than 5 % more expensive than the
gasoline version, while the diesel hybrid is roughly 15 % less energy consuming
and less than 5 % more expensive than the gasoline hybrid.
5. The best-performing vehicle of the group is the direct hydrogen fuel cell vehicle,
with nearly 60 % lower energy consumption than the evolving ICE vehicle, at
about a 40 % price increase. However, this number only accounts for the vehicle
cycle, which does not include the manufacturing and distribution of hydrogen.
6. The reformer fuel cell vehicles, which uses liquid fuels to process for hydrogen on
board, perform significantly worse than the hydrogen fuel cell and have the
highest prices of the group studied, with the gasoline reformer consuming more
fuel, emitting more carbon, and having a higher cost than the methanol version.
Overall, the gasoline and methanol reformer FC vehicles uses 130 % and 70 %
more energy than the hydrogen FC vehicle, and about 4 % and 30 % less energy
respectively than the evolving gasoline ICE vehicle. At a cost over 55% and 50 %
more expensive than the evolving baseline for the gasoline and methanol reformer
FC vehicles, these technologies appear rather unfeasible for 2020.
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7. While the battery electric propulsion system require the lowest energy input (as
electricity) to the vehicle, with either the optimistic or conservative assumptions
about future battery technology, when allowance is made for the efficiency of
electricity production, distribution, and actual battery recharging, the total energy
consumed is dramatically higher. Hence, it is not appropriate to compare the EV
to other technologies based only on the vehicle cycle. Also, given the battery
technology considered, the EV is about 45 %higher in price than the baseline.
To compare these technologies more comprehensively, a larger report including the fuel,
manufacturing, and vehicle cycles will be available from the MIT Energy Laboratory.
7.0 Societal Implications
The automobile revolution has exploded over its short existence of a century. From a few
daring prototypes running on unpaved roads, it has grown in the United States to include
two of the most powerful global industries in petroleum and automobiles, multiple cars
per household with about three passenger vehicles for every four Americans 24 , and
highways and urban roads over the entire country. But this industrial phenomenon has a
price that we have been passively paying in the past, now, and for a long time to come.
Virtually all personal transportation and recreational vehicles in the United States are
powered by petroleum, from the family car to the lawnmower, from the weekend boat to
the snowmobile. While serving transportation demands of people, the combustion of
fossil fuels for energy is also a destructive burden on the environment in which all living
beings dwell, and the dependence on fossil fuels for our perceived daily needs is a barrier
to world peace for which we all aspire.
In the next three subsections, I will put this thesis in a context of society by explaining
first how our oil dependence creates what may seem to be external or institutionalized
problems, then why individuals in industrialized countries share the responsibilities of
these problems, and finally how people could strive toward a better civil society simply
with their daily decisions and actions.
7.1 Accompanying Penalties
Many problems associated with oil and cars may be attributed to a few individuals at the
top having too much power to protect their self-interest. Starting at the beginning of the
process, the extraction of fossil fuel, there is already destruction. The most contemporary
example is Occidental Petroleum: to satisfy world demand and to make a profit, the
company has been trying to drill in Colombia for the past eight years and coming in
direct confrontation with the indigenous U'wa people who are trying to protect their
homes and ancestral lands. The Colombian military and para-military, with funds coming
from U.S. taxpayers channeled through the U.S. government, including the most recent
attempt of US$ 1.7 billion military aid package, was used to forcibly remove people from
the proposed drill site. Currently, a court injunction by the Colombian courts preventing
Occidental from drilling has just been overturned, and the battle between a multi-billion
transnational corporation and three thousand marginalized indigenous people continues.
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The Gulf War, originally presented to the public as the defense of a small country
invaded by an aggressor a decade ago, is now generally accepted as a war for oil.
Publicly disclosed documents make it general knowledge that the industrialized powers
provided Iraq with all of its war-making capabilities, including chemical and biological
weapons of mass destruction, prior to 1990. Furthermore, the contradiction to other
similar, contemporary, global problems is clear: in regions with little U.S. interest, there
was no intervention despite worse atrocities and human rights violations. The current and
continuing intervention in the region is to defend the same interest, oil. For years, Turkey
was the biggest recipient of U.S. military aid, and now is a NATO member and provides
the bases for U.S. military action in the region. And over the past decade, after being
"bombed back to the stone ages" according to President Bush, Iraq continues to suffer
under a comprehensive sanctions that has directly resulted in 1.7 million deaths by U.N.
estimates, leading to condemnations by numerous countries, human rights groups, and
private citizens, as well as the resignations of three high-ranking officials in the U.N.
The power game for oil extends from its worst consequences, the oppression of weaker
peoples, to more long-term effects, namely the environment and its subsequent health
impacts. Eco-system stability, viability, and diversity, including natural habitats and
wildlife refuges, are constantly under attack from companies eager to find new drill sites,
causing many citizen groups to expend precious time and energy to fend their attempts
off. Meanwhile, current drilling stations, tanker ships, and local refueling stations leak
and spill toxic materials into the ocean, earth, and groundwater, but with the damages
shared unfairly among the affected people, and the altered eco-system, and sometimes,
the responsible party.
While most of the suffering are out of sight and out of mind, the affluent population of
the world do notice local air quality, directly affected by the pollutants that come out of
the tailpipes of their vehicles. Over the history of emissions control, the pollutants
released from vehicles have been dramatically reduced. But despite the past success and
proven health effects, the industries continue to drag the change process. Fuel economy
and emissions regulations continue to be a struggle. Gas-guzzler taxes and CAFE
requirements, already filled with loopholes such as their special status for passenger
vehicles listed as light-duty trucks and the consecutive years of violation prior to penalty,
have been on a standstill for almost a decade, despite inflation, better technology, and a
sustained economic boom driving more people to buy more powerful, less fuel economic
vehicles. The recent Tier 2 regulations, slow to be enforced eight years from now for the
most polluting types of vehicles, was also fought against by the oil industry for the
difficulty in transition to low sulfur content gasoline, despite already being in production
(at 30 ppm Sulfur or lower) elsewhere in the world. And perhaps the grossest example of
corporate interests over people welfare is the case of lead in gasoline. Although the health
dangers were clearly understood and alternatives were available, lead, foreign to
petroleum, was purposely added to gasoline to produce better combustion properties. The
resulting health impact was so grave and so easily preventable that it was finally phased
out of gasoline ten years ago, but only in countries with a strong consumer base. The oil
industry continues to export leaded gasoline to developing countries.
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Disregard for responsibility is also evident in the case of global climate change, the topic
of numerous international conferences, negotiations, and treaties. While predicting the
exact changes is debatable, it is clear that the uncontrolled, geometrically-increasing
anthropological carbon input into the atmosphere will result in regional and global
climate change. The problem is so vast that even if the world succeeds in capping carbon
emission to the levels of 1990, there will still be a net increase, just one that is more
steady and predictable. Nowhere else in the world is the science questionable except in
the U.S., where the Big Three automakers, Ford, Chrysler, and lastly General Motors,
took on positions contrary to their own European and Asian operations, before finally
withdrawing from the Global Climate Coalition within the last year because of civic
pressures. Even though they made up the backbone of support for the cover propaganda
group denying the legitimacy of global climate change, their names do not appear on the
materials during their time of support. Hiding behind a few unknown scientists and using
a nonprofit front to lobby their corporate agendas, this powerful industry put up an active
obstruction to societal interests and stall changes intended to avoid common aversions.
But while corporate and governmental forces seem to generate and perpetuate many
problems in providing energy and transportation needs, the link between individuals and
institutions cannot be decoupled.
7.2 Self-Constructed Problem
Intended to address the climate change issue, but inescapably bound to this context of
destructive societal implications, this study was performed to assess the potentials of
technology in alleviating the carbon emission problem. If the frame of reference is a car,
then certainly, a less energy consuming car is desired. However, for an intellectual
institution set in a society of abundance, we are obligated to look at and act within the
bigger picture. Part of that picture includes the abuse of power by corporations, but the
other part is the people who, with our lifestyles and self-interest, often unknowingly and
unintentionally supply the power that sustains the institutions.
The fascination and dependence on automobiles are created by people. Our automotive
culture has chosen a lifestyle of more cars, bigger cars, and more miles traveled, a
lifestyle that takes 86 % of trips and travels 91 % of the miles in private passenger
vehicles , a lifestyle that spends 63.6 - 81.3 minutes (female - male) per day inside a
vehicle and occupied with 1.59 people on average2 5 . This attitude is exemplified during a
Univision Town Hall meeting this February, a Los Angeles resident that takes two buses
to get to work every day asked Texas Governor and Presidential Candidate George W.
Bush how the Los Angeles public transportation system could be improved. Bush
responded, "My hope is that you will be able to find good enough work, so youll be able
to afford a car." 2 6
The sacrifices for fossil fueled automobiles are accepted by people. Our automotive
society has gradually become content with highways over community space, aiding the
segregation communities so people can bypass undesirable areas on their way elsewhere;
with wider streets over play space, where a few speed bumps are supposed to reclaim the
loss of neighborly interactions and children's play area; and with parking lots over green
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space, where the typical parking space, idle during the day and empty at night, is bigger
than a worker's office space. In addition, storm water runoff washes all the pollutants and
toxic fluids from automobiles directly into bodies of water, contaminating swimming and
drinking water in communities everywhere.
The policies to secure fossil fuels are rationalized by people. Our automotive mentality
has decided on a set of rationales that gasoline tax increase will always be opposed,
despite the fact that gasoline prices in the U.S. is cheaper than anywhere else in the
developed world by two to five-fold; that the oil and auto industries will be granted
corporate privileges and lobbying dominance so that they can manipulate regulations
designed to protect civilians, including safety requirements such as the automatic
shoulder belt option instead of a driver-side airbag in the early 1990's; and that political,
economic, and military actions elsewhere in the world is an acceptable means to secure
resources, even if it means repressing other peoples and creating greater inequity. It is
incredibly ironic and intolerable that we have come to accept today suffering and death,
in addition to environmental destruction, to obtain a product derived from death millions
of years ago.
With concerns for our immediate self-interest, we are neglecting our mutual self-interest,
one not just applicable to one person at one instant, but to all beings over a sustained
frame of time.
7.3 Civil Response
The energy reduction projections of 40 % for the evolutionary vehicle and 75 % for the
highest potential advanced vehicle, as compared to today's average passenger car, would
be offset by the increasing number of vehicle miles traveled, as well as the increasing
number of automobiles in the world, especially with the global automakers targeting new
markets in developing countries, in particular China. Meanwhile, even if some vehicles
are completely non-carbon emitting, they are still not enough to balance the fleet, and net
anthropogenic carbon will continue to build up in the atmosphere, just from the
transportation sector. Given the severity and persistence of the global climate change, and
given its root causes associated with other societal and environmental injustice,
technology alone is simply insufficient in dealing with the problem.
Instead, a civil response is required to begin to take the first step to contain the adverse
effects of our own creation that spans from climate change to global justice. While
transportation may be a necessity, and while it would be impossible to phase out the
fossil fuel automobile overnight, we as citizens still have many options in our daily lives
to make change. Our everyday decisions and action, when thought out not just with selfinterest, but also with inclusion of all, not only has more effect than technological
upgrades, but ultimately will be the foundation of building the more ideal human
community and civilization.
We can decrease dependence by considering alternatives. First, when, or rather if,
choosing an automobile, we can use one that fits the purpose. There are many options
with desirable features, such as high space utilization or good performance, and also have
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high efficiency technologies or alternative and cleaner fuels. Second, communities can
imagine and explore innovative ideas such as car-sharing (operating in some cities in
Europe) or inexpensive, short-term rentals. Third, we can move further away from the
automobile by considering alternatives in our modal choices, such as walking, rollerskating, and biking for short distances, and mass public transportation, such as buses,
boats, and trains, for longer distances. Increase uses of these modes would result in a
greater demand and better supporting infrastructure. Finally, even before the modal
choice, we can evaluate the task and analyze whether the intended purpose requires the
distance or the trip itself.
We can weigh more carefully the tradeoffs in planning for cities. Competent urban street
and road planning could alleviate traffic jams and establish pedestrian zones without
sacrificing mobility. One poor example is the Big Dig project in Boston, which despite
putting layers of roads underneath the ground, has no bike lanes planned for the surface.
Commuter hubs could aid commuters and concentrate parking, saving valuable space in
urban areas for other uses. Public transportation, in general, requires citizen support and
continued or increased funding to provide route expansions and improved services.
Workplace incentives could also encourage alternative modes of travel and alleviate high
traffic areas which are major sources of wasted energy and urban pollution.
We can advocate for corporate accountability and sustainability research. Support for
civic watchdog organizations for corporations could help disseminate pertinent
information for intelligent decision making, and to provide a forum for citizen dissent and
input. As a participatory democratic society, we could also work toward more effective
accountability for governmental regulatory agencies. Internalizing the real cost of
"externalities" with pricing, taxing, or fining policies could help repair the damages
caused and fund public research, for example for renewable energy. A great deal of
cleaner and sustainable energies and technologies are already available, but cannot
survive on market because the dirty technologies are not paying their full costs.
Above all, first and foremost, we have to support human welfare. We have to put priority
on safety technologies and policies in cars design and road planning. We have to give
priority to health improvements, particularly preventable illnesses and injuries. We have
to effectively oppose corporate exploitation of people or the environment, regardless of
how immediate they are to our own lives; we cannot allow blood for oil foreign policies
that twists our personal self-interest into aggressive national interest.
From the highway fatalities that started the national Emergency Medical Services to the
court conviction of corporate collusion to undermine urban public transportation, our
automotive culture has been both a blessing and a curse. Faced with well-understood
environmental and social problems resulting from our dependence on automobiles and
petroleum, we have an opportunity to exercise our choices and to use our daily lives to
resolve these issues. Our wishes for more comfort in transportation and energy and our
wishes for happiness in our lives are not mutually exclusive but intricately connected. In
working for all people so that everyone will have basic needs, choices, and dignity in
their daily experience, we will create a world with justice and equity, one that will be
more enjoyable for all.
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Appendix A: Vehicle Mass Projection and Distribution
Table 4.1 reports our projections of vehicle mass by component for all vehicles
examined. The estimated mass distribution of the 1996 baseline vehicle is based on the
mass distribution of a 1990 Ford Taurus (OTA, 1995) and a study by the Ultra-light Steel
Autobody (ULSAB) Consortium that especially examined the mass of vehicle
components for a range of recent passenger cars (ULSAB-AVC Consortium, 1999).
Based on the vehicle mass distribution of the 1996 baseline vehicle, the distribution of all
other vehicles was projected, using the following simple approach. The 2020 baseline
vehicle distribution was derived by multiplying the mass of the body structure, other
body parts, and steering and brakes by 0.85 to reflect the approximately 15% mass
reduction potential of high-strength steel compared to mild steel. For all advanced
vehicles, the 1996 baseline vehicle mass of these same components was multiplied by
0.65 to simulate the 35% mass reduction due to aluminum substitution. The mass change
of the propulsion system resulted largely through the vehicle propulsion system modeling
described in this section and exogenously specific power-to-mass ratios of the major
components, determined at 0.9 kW/kg for an advanced gasoline engine, 0.6 kW/kg for an
advanced diesel engine, 1.5 kW/kg for an electric motor, and 0.47 kW/kg for a fuel cell
stack.
The mass of suspension and frame of any 2020 vehicle was estimated by multiplying the
chassis mass of the 1996 baseline vehicle with the ratio of the projected mass of vehicle
body, propulsion system, and interior of the 2020 vehicle and the mass of these
components of the 1996 baseline vehicle. This simple approach ensures that suspension
and frame of all projected 2020 vehicles is sufficiently strong to carry the mass of the
projected body, propulsion system, and interior through eventually adding mass to the
chassis (row: Extra Support). The maximum extra support mass is 70 kg for the hydrogen
fuel cell vehicle, where propulsion system mass increases by 43% compared to the 1996
baseline vehicle.
Other notable changes in component mass form the 1996 baseline vehicle include the
transition from automatic transmission to auto-clutch and continuous variable
transmission, and a reduction in wheel and seat mass due to a larger use of magnesium. In
accordance to (ULSAB-AVC Consortium, 1999), we added 25 kg of mass to all 2020
vehicles to ensure the satisfaction of 2004 crashworthiness standards.
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1/4-6
Appendix B: Estimated Vehicle System Retail Prices
Given the lack of a cost model and detailed input data that would allow a estimate of the
manufacturing costs of more fuel-efficient vehicle technology, our retail price estimates
are based on the following approach. The price increments of the technologies examined
are derived from a literature review and in most cases were discussed with
representatives from the automobile industry (Dietrich et al., updated paper in
preparation).
Technology improvements and changes that enable higher vehicle fuel efficiency do not
necessarily increase the retail price. For example, today's automobile tires have 30%
lower rolling resistance compared to those in the mid-1980s, 25% increase in lifetime,
15% reduction in noise, and 7% improved wet-road braking, but identical costs (Birch,
1996). Based on that experience, we expect that if new tire technology is introduced
gradually into the automotive market, future (2020) tire technology will continue to
provide lower rolling resistance at the same price through improving understanding of the
problems and opportunities, and market mechanisms. As a consequence of assuming that
some technology based improvements do not increase cost, our integrated retail price
estimates may be towards the lower end of expected price changes.
The starting point for our estimates is the price of the 1996 baseline vehicle of US$(1997)
17,200. The retail price of all other vehicles is obtained by adding or subtracting the price
of vehicle components that are added to or removed from the configuration of a particular
vehicle, to or from the price of the baseline vehicle. The resulting retail price estimates
are presented in Table 4.10 for all ten vehicles (see table notes for assumptions).
The retail price of the evolving baseline vehicle increases by 5% from about US$ 17,200
to 18,000; a rise in mass-specific costs from US$ 13/kg to 16. This increase is broadly in
the range of historical cost developments (see Figure 4.9). (The slightly lower retail price
of the 1996 baseline vehicle results from it being the base vehicle price, the only price
information we could get for all vehicles sold in the U.S. in a given year). An additional
factor for the higher historical numbers is the inclusion of minivans and sport-utility
vehicles in the data set; these vehicles are typically more expensive than sedans.
The retail price of all other eight projected vehicles in 2020 ranges from US$ 19,400
(gasoline-fueled advanced mechanical drivetrain vehicle) to nearly US$ 28,200 (gasolinefueled fuel-cell automobile), an increase by 8 to 57% over the evolving baseline vehicle
in 2020. Each propulsion system/vehicle combination covers a specific portion of this
price range. (Note all vehicles except the baseline are "advanced vehicles": i.e.,
incorporate substantial new technology to reduce driving resistances.) While advanced
vehicles with a mechanical drive train are at the lower end of this price range, i.e.,
between US$ 19,400 and 20,500, hybrid vehicles have a retail price between US$ 23,200
and US$ 24,300. At the high price end are fuel cell vehicles and the battery electric
vehicle with retail prices of US$ 25,500 (hydrogen-fueled) to 28,200 (gasoline-fueled).
Table 4-6 reports the cost estimates in more detail.
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25
20 -
Baseline vehicle in 2020
60
153000
0
Baseline vehicle in 1996
co0) 10 -
0
White data points: historical development of
U.S. light duty vehicles (domestically produced and imported between 1976 and 1997)
5-
0 1
1970
1975
1980
1985
1990
1995 2000
Year
2005
2010
2015
2020
2025
Figure 21: Mass-specific costs of the baseline vehicle in 1996 and 2020 (black
rectangles) and the historical development of the new U.S. automobile fleet between
1976 and 1997 (white rectangles). The retail price of the baseline vehicle is slightly
below the historical level, since (1) it reflects the base vehicle price, i.e., without any
extras, and (2) the historical numbers likely include minivans and sport-utility vehicles
that are typically more expensive than sedans.
Among the projected vehicle retail prices, the major uncertainty is associated with that of
fuel cell vehicles. We have estimated the price of a fuel cell system to be US$ 60/kW,
which is close to the lower end (of US$ 50-100/kW) that can be found in the literature
(see, e.g., Ogden et al., 1999). In order to be cost-competitive with ICE powered hybrid
drive train vehicles, the fuel cell system price would need to be considerably reduced
from US$ 60/kW to about US$ 20/kW, all other factors being equal. However, if using
instead of the more conservative estimate of the electric motor price of some US$ 42/kW,
a more optimistic number of US$ 20/kW (which is within the range given by Ogden et
al., 1998), the fuel cell price to achieve cost-competitiveness to a ICE hybrid vehicle
would need to be US$ 40-45/kW, a more feasible ICE.
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Table 22: Retail price estimates of the ten examined vehicles.
Baseline Vehicle
Engine
Credit for Downsizing
GDI
VVLT
Hybrid/Fuel Cell Systems
Fuel Cell
Reformer (incl. exhaust gas cleaning)
Fuel Tank
Electric Motor (incl. power el.)
Single Stage Reduction Transmission
Battery
current
SI ICE
baseline
SI ICE
advanced
SI ICE
advanced
CI ICE
advanced
SI
Hybrid
advanced
CI
Hybrid
advanced
FC
Hybrid
advanced
FC
Hybrid
advanced
FC
Hybrid
advanced
Electric
gasoline
gasoline
gasoline
diesel
gasoline
diesel
gasoline
methanol
hydrogen
electricity
direct
17187
direct
17187
direct
17187
direct
17187
-4048
-4048
-4048
-4048
5712
1904
5365
1904
5018
4652
159
1285
4393
155
1216
650
4133
151
1125
-100
4107
151
7482
-430
-430
-430
-430
auto-clutch auto-clutch auto-clutch
auto
17187
17187
17187
17187
1500
-360
-360
-240
375
500
225
300
CVT
17187
-360
375
225
CVT
17187
1500
-360
1525
109
2295
1525
109
2295
Exhaust Gas Cleaning
300
Tier 2
225
400
163
293
1600
150
1600
150
1600
150
1600
150
1600
150
1600
150
1600
150
1600
150
20500
19.0
23300
21.0
24300
20.9
28200
20.4
27500
21.3
25500
21.3
26100
21.9
Vehicle
Weight Reduction
Aerodynamics
TOTAL
Total Vehicle Price
$ per kg Vehicle Weight
I
17200
13.0
18000
16.0
19400
19.0
Table Notes: The credit for engine downsizing is assumed to be US$ 120 per cylinder. The retail price increment (RPI) of GDI and VVLT are assumed to be
of
US$ 500 and 300, respectively for a 4-cylinder engine; we assumed that these figures scale as the number of cylinders (Dietrich et al., 1998). The RPI
In
estimate.
EEA
the
than
lower
but
136
US$
of
estimate
EPA
than
higher
is
engine
4-cylinder
satisfying the Tier 2 emission requirements of US$ 300 for a
emission
of
RPI
the
that
assume
we
Again,
1997).
(EEA,
73%
EEA's
the
and
26%
EPA's
the
of
instead
100%
of
(RPE)
addition, we use a retail price equivalent
control technology scales as the number of cylinders. We assumed the corresponding RPI of diesel exhaust gas catalyst to be one-third higher compared to the
one for gasoline engines, because it represents a completely new system and satisfies two functions, reduction of gaseous emissions and particulates. The RPI of
rear
US$ 1,600 for vehicle weight reduction results from the extra investments for an aluminum-body and closures and the aerodynamics for panels to cover the
cylinder
a
four
above
1500
US$
is
engine
diesel
turbo-charged
injection,
wheels and the vehicle's underbody (see Dietrich et al., 1998). The RPI of the direct
gasoline engine. The RPI of asynchronous motors, converters, and power electronics is based on the equation RPI (US$(1990)) = 310 + 31 - kW(peak) (OTA,
revised
1995) and that of a single stage reduction transmission RPI (US$(1990)) = 90 + 0.62 - kW(peak) (Dietrich et al., 1998). The battery retail price reflects
in the
i.e.,
20/kW,
is
US$
reformers
fuel
of
RPI
The
1999).
(Davis,
3.75/kWh
of
US$(1996)
target
Consortium
Battery
Advanced
U.S.
the
of
the upper level
430
is
US$
middle of the range assumed by Ogden et al. (1998). The credit of a three way catalyst, applicable to all fuel cell and the battery electric vehicle
a
30/kW,
US$
to
amount
(DeLucchi, 1989); these vehicles also experience of credit for the drop of internal combustion engine and transmission, assumed to
60/kW.
US$
to
be
typical number of the automobile industry. The RPI of fuel cells was assumed
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44/1"46
REFERENCES:
1.
"World Total Energy Consumption," United States Department of Energy,
<www.eia.doe.gov/oiaf/ieo95/tbls.html>.
2. Ward's Automotive Yearbook 1997, 591h Edition, Ward's Communications, 1997.
3. Motor Vehicle Facts & Figures 1998, American Automobile Manufacturers
Association, 1998.
4. Office of Technology Assessment. Advanced Automotive Technologies: Visions of a
Super-Efficient Family Car, OTA-ETI-638, Washington D.C., 1995.
5. L. Guzzella, A. Amstutz. "Quasi-Stationaren-Simulations," Matlab programs and text
Benutzeranleitung, Laboratorium fur Motorsysteme, Institut fUr Energietechnik,
ETH-Zurich, 1998.
6. EPA annual Fuel Economy Guide. <www.epa.gov/omswww/mpg.htm>, 2000.
7. "New Ford Hybrid Electric Car Tops 70 mpg," Ford Motor Company: Better Ideas:
Environment, <www.ford.com>, 2000.
8. "Detroit Auto Show: GM Rolls out Fuel Cell "Precept" Concept, Claims 500 Mile
Range," The Hydrogen & Fuel Cell Letter, ISSN 1080-8019, 2000.
9. Michael Kluger and Denis Long. "An Overview of Current Automatic, Manual and
Continuously Variable Transmission Efficiencies and their Projected Future
Improvements," SAE Paper 1999-01-1259, 1999.
10. Dale Chon and John Heywood. "Performance Scaling of Spark-Ignition Engines:
Correlation and Historical Analysis of Production Engine Data," SAE Paper 2000-010565, 2000.
11. "Hybrid Electric Vehicle Component Information" Department of Energy,
<http://www.hev.doe.gov/components/batteries.html>, August, 1999.
12. United States Advanced Battery Consortium Battery Criteria: Commercialization,
<www.USCAR.org>, May, 2000.
13. Honda Insight, <www.honda.com>, 2000.
14. David J. Friedman. "Maximizing Direct-Hydrogen PEM Fuel Cell Vehicle Efficiency
- Is Hybridization Necessary?" Society of Automotive Engineers, 1999-01-0539,
1999.
15. C.E. Thomas, et al. "Societal Impacts of Fuel Options for Fuel Cell Vehicles,"
Society of Automotive Engineers, 982496, 1998.
16. see reference 2.
17. Dieter Stock and Richard Bauder. "The New Audi 5-Cylinder Turbo Diesel Engine:
The First Passenger Car Diesel Engine with Second Generation Direct Injection,"
Society of Automotive Engineers, 900648, 1990.
AuYeung
45/461
18. Toyota- Prius- Specifications. <toyota.com>, May, 2000.
19. James Adams, et al. "The Development of Ford's P2000 Fuel Cell Vehicle," Society
of Automotive Engineers, 2000-01-1061, 2000.
20. GM EV1- Specifications. <www.gm.com>, 2000.
21. "Fuel Squeeze Drives Interest in Concept Cars," Environmental News Service, 2000.
22. "Electric Assist," Electomotive, Inc., 9131 Centreville Road, Manassas, VA 02110.
23. H.L. MacLean, L.B. Lave. "Addressing Vehicle Equivalency to Facilitate Meaningful
Automobile Comparisons," Society of Automotive Engineers, 1998.
24. U.S. population figures in 1997, <www.census.gov>.
25. Nationwide Personal Transportation Survey 1995, U.S. Department of
Transportation.
26. quote from <newscom.com>, Feb.28, 2000.
Other Sources:
" A.F. Burke. "Hybrid/Electric Vehicle Design Options and Evaluations," Society of
Automotive Engineers, 920447, 1992.
-
Bosch Automotive Handbook, 4th Edition, Robert Bosch GmbH, 1996.
-
"Detroit Auto Show: Ballard Announces Production-Ready Fuel Cell Module, Hints
at Factory Plans," The Hydrogen & Fuel Cell Letter, ISSN 1080-8019, 2000.
-
Greg Ayres. "Consumer Incentives to Reduce Greenhouse Gas Emissions from
Personal Automobiles," Society of Automotive Engineers, 1999-01-1307, 1999.
-
Hartmut LUders, Peter Stommel, Sam Geckler. "Diesel Exhaust Treatment- New
Approaches to Ultra Low Emission Diesel Vehicles," Society of Automotive
Engineers, Society of Automotive Engineers, 1999-01-0108, 1999.
-
"Issues in Midterm Analysis and Forecasting 1999," Energy Information
Administration, Department of Energy, 1999.
m
John B. Heywood. Internal Combustion Engine Fundamentals, McGraw-Hill, Inc.,
1998.
-
"NAIAS Highlights: Concepts," Automotive Engineering International, March 2000.
-
P.J. Shayler, J.P. Chick, D. Eade. "A Method of Predicting Brake Specific Fuel
Consumption Maps," Society of Automotive Engineers, 1999-01-0556, 1999.
-
Richard K. Stobart. "Fuel Cell Power for Passenger Cars- What Barriers Remain?,"
Society of Automotive Engineers, 1999-01-0321, 1999.
-
William L. Mitchell, M. Hagan, S.K. Parbhu. "Gasoline Fuel Cell Power Systems for
Transportation Applications: A Bridge to the Future of Energy," Society of
Automotive Engineers, 1999-01-0535, 1999.
AuYeung