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N. Brinkman,
GM Global Research & Development, Warren, MI, USA;
Dr. U. Eberle, Dr. V. Formanski,
Prof. Dr. U. D. Grebe, R. Matthé,
General Motors Europe, Rüsselsheim, Germany
Vehicle Electrification – Quo Vadis?
Fahrzeugelektrifizierung – Quo Vadis?
Fortschritt-Berichte VDI, Reihe 12 (Verkehrstechnik/Fahrzeugtechnik),
Nr. 749, vol. 1, p. 186–215, ISBN 978-3-18-374912-6
33. Internationales Wiener Motorensymposium 2012
N. Brinkman, GM Global Research & Development, Warren,Michigan, U.S.A.;
Dr. U. Eberle, Dr. V. Formanski, Prof. Dr. U.D. Grebe, R. Matthé, General Motors Europe,
Rüsselsheim, Germany
Fahrzeugelektrifizierung – Quo Vadis?
Vehicle Electrification – Quo Vadis?
Kurzfassung
Die Entwicklung der elektrischen Fahrzeugantriebe von der Erfindung des Kraftfahrzeugs
bis zur Gegenwart wird in dieser Veröffentlichung beschrieben und es wird ein Ausblick
auf den zu erwartenden Fortschritt gegeben. Unter Berücksichtigung der
Randbedingungen verschiedener Energieketten und technischer Grenzen aller
Systemkomponenten eines elektrischen Antriebsstrangs werden sinnvolle Einsatzfelder
elektrifizierter Fahrzeugantriebe aufgezeigt.
In Zukunft werden die Antriebstränge zunehmend elektrifiziert. In einigen Anwendungen
werden batterieelektrische Fahrzeuge wettbewerbsfähig, was besonders für den Einsatz
im städtischen Kurzstreckenverkehr gilt. Für solche Anwendungsfälle eignen sich
Fahrzeugkonzepte vom Kleinwagen bis zum Stadtbus. Elektrofahrzeuge mit
Reichweitenverlängerung erlauben weitere Fahrtstrecken und können somit vollwertige
Erstfahrzeuge darstellen. Dadurch wird das Elektrofahrzeug für größere Kundengruppen
einsetzbar. Wasserstoffbetriebene Brennstoffzellenfahrzeuge fahren jederzeit ohne lokale
Emissionen und lassen sich schnell betanken. Die Anwendung der
Brennstoffzellentechnologie ist für die meisten Fahrzeugsegmente sinnvoll und im
wesentlichen technisch nur durch die notwendigen Baugrößen der Antriebskühlung und
der Wasserstoffspeicher für besonders hohe Anforderungen begrenzt.
General Motors ist davon überzeugt, dass der Marktanteil der elektrischen Antriebe
signifikant zunehmen wird, geht aber auch davon aus, dass die konventionellen Antriebe
mit Verbrennungsmotoren noch eine lange Zukunft haben – wenn auch viele eine
Unterstützung durch Hybridisierung erhalten werden.
Abstract
This publication describes the development of electrified propulsion systems from the
invention of the automobile to the present and then provides an outlook on expected
technology progress. Vehicle application areas for the various systems are identified
based on a range of energy supply chains and the technological limits of electric
powertrain components.
GM anticipates that vehicle electrification will increase in the future. Battery-electric
vehicles will become competitive for some applications, especially intra-urban, short-
distance driving. Range-extended electric vehicles provide longer driving range and offer
full capability; with this technology, electric vehicles can serve as the prime vehicle for
many customers. Hydrogen-powered fuel cell-electric powertrains have potential for
application across most of the vehicle segments. They produce zero emissions during all
phases of operation, offer short refueling times, but have powertrain cooling and hydrogen
storage packaging constraints.
33. Internationales Wiener Motorensymposium 2012
While the market share of electrified vehicles is expected to increase significantly, GM
expects conventional powertrains with internal combustion engines to also have a long
future – however, a lot of them will be supported by various levels of electrification.
1. History of Vehicle Electrification
[1-6] In the early days of the automobile, various propulsion systems competed. The
internal combustion engine used by Carl Benz in his Tricycle vehicle (1885) continues to
dominate the market today, but the first vehicle to exceed 100 km/h was “La Jamais
Contente,” an electric vehicle driven by Camille Jenatzy, a Belgian race driver and vehicle
constructor.
Figure 1 – Early history of vehicle electrification, 1899-1973 [1-6].
Bild 1 – Frühgeschichte der Fahrzeugelektrifizierung, 1899-1973 [1-6].
Countless companies in the United States and Europe built electric vehicles, e.g., the
Detroit Electric Car Company, Oldsmobile, and Siemens. In the 1910s, electric cars were
popular in North America and owners included Thomas A. Edison and Clara Ford. They
were considered luxury vehicles because they were quiet and easy to operate. GMC also
produced electric trucks from 1911 to 1917.
In 1911, Charles F. Kettering [1] invented an all-electric starting system that was
introduced in the 1912 Cadillac. The electric self-starter made the internal-combustion-
engine car easier to operate since it no longer required a “chauffeur” to crank the engine
by hand. The electrification of the internal combustion engine helped to defeat the “electric
car” in the first decades of the 20th century. Its arrival signaled the rapid expansion of
combustion-engine-powered vehicles. In Kettering’s words, it was a perfect example of
“the right thing to do at the time it has to be done.”
The last electric vehicle companies went out of business in the 1930s and it was not until
the 1960s when General Motors began to develop electric vehicle studies based on the
rear-motor-driven Chevrolet Corvair. The Electrovair 1 (1964) and 2 (1966) were equipped
with silver-zinc batteries used in the aerospace programs of that era. Around the same
33. Internationales Wiener Motorensymposium 2012
time, GM also developed the Electrovan (1966), the first fuel cell vehicle to use hydrogen
and oxygen as fuel. It was powered by an alternating-current (AC) induction motor.
GM’s early electric vehicle research was motivated by (1) the search for clean automotive
propulsion to address air pollution and (2) technical progress on aerospace technology
gained from a number of GM divisions, including Delco Electronics, contracted to build the
“Lunar Rover,” the vehicle used by the Apollo astronauts to drive on the moon.
In 1973, the Electrovette, which was based on the Chevrolet Chevette and used nickel-
zinc batteries, was considered as an option to address increasing gasoline prices, but gas
prices did not exceed $2.50 per gallon (<$0.6 per liter), so the effort stalled.
Continued progress in electronics, electric motors, and solar cell technology in the 1980s,
along with GM’s investment in Hughes Electronics, led to the design in 1987 of the GM
Sunraycer, a vehicle with 6 m² of solar cells, lightweight structure, and aerodynamic
shape. This car won the first solar race across Australia running at an average speed of 67
km/h.
Figure 2 – Lunar Rover (1972) and GM Sunraycer (1987).
Bild 2 – Lunar Rover (1972) und GM Sunraycer (1987).
Encouraged by EV performance, GM engineers considered how to put this technology on
normal roads for the everyday driver. The result was the GM Impact concept car, unveiled
in 1990 with two AC induction motors totaling 85 kW and an aerodynamic drag coefficient
of 0.19. The Impact’s acceleration from 0-to-96 km/h in 8 seconds was impressive and
intended to remove any prejudice about slow-moving electric vehicles. The power inverter
contained 228 MosFET transistors, demonstrating progress in power electronics although
not quite ready for production.
The GM Impact was the forerunner of the GM EV1 electric vehicle, introduced in 1996 for
lease in California, Arizona, and New York. Through 2003, more than 1000 EV1 were
produced. The first generation was equipped with a lead-acid battery (312V and 18.7
kWh); beginning in 1999, the second-generation vehicle featured a nickel-metal hydride
battery (343V and 26.4 kWh). EV1’s propulsion system was a single 102-kW AC induction
motor with an Insulated-Gate Bipolar Transistor (IGBT)-based power inverter. The
vehicles, which qualified for Zero Emission Vehicle (ZEV) credits, were popular with many
drivers, who were impressed by the “EV” driving experience but unimpressed by the
limited driving range.
33. Internationales Wiener Motorensymposium 2012
Figure 3 – Modern era of vehicle electrification: From the GM Sunraycer to the Chevrolet
Volt and Opel Ampera [1-6].
Bild 3 – Fahrzeugelektrifizierung in der jüngeren Geschichte: Vom GM Sunraycer zum
Chevrolet Volt und Opel Ampera [1-6].
In Europe, Opel developed electric vehicles based on production vehicles. It tested the
Opel Impuls, based on the Kadett, in 1990. The first Impuls still had a four-speed manual
transmission with a 10-kW direct-current (DC) shunt electric motor powered by a thyristor
controller and a 12-kWh,120V nickel-cadmium battery. The vehicle’s top speed was 100
km/h and the maximum range was 80 km.
In 1991, the propulsion system of the GM Impact was integrated into the new Opel Astra
Wagon and the Impuls 2 was presented at the Frankfurt motor show (IAA). It features 32
lead-acid modules, which were integrated into four compartments not compromising the
usability of the car. The five-seat wagon with sporty performance received positive
feedback for its agility and required only 12 seconds for 0-to-100 km/h acceleration, which
was enabled by two AC induction-drive motors providing 85 kW total power. The top speed
was limited to 120 km/h and the range provided by the 13.2-kWh lead-acid battery
exceeded 80 km.
For an electric vehicle field test on Ruegen Island in the Baltic Sea, Opel developed the
Impuls 3, equipped with nickel-cadmium batteries from DAUG-Hoppecke or “Zebra”
sodium-nickel chloride (NaNiCl) batteries from AEG Anglo Batteries. The station wagon
was propelled by a Siemens-produced AC induction motor with a reduction gearset. Ten
Opel Astra Impuls 3 vehicles participated in the field test and demonstrated versatility and
performance in everyday operation. Nine out of 10 users stated that they would buy the
vehicle for its very good driving performance and it would serve their needs. The Opel
Impuls with the Zebra battery could drive up to 180 km per charge, but the recharge time
at a 230V, 16 A outlet required up to 9 hours.
33. Internationales Wiener Motorensymposium 2012
For commercial applications, Opel developed an EV conversion of the Opel Corsa Combo
delivery van. One version used Zebra batteries and an on-board charger and a second
version used zinc-air batteries and required a battery exchange when depleted. The zinc-
air batteries provided energy for up to 300 km of range, but required mechanical and
chemical recharging. In addition, compressors and carbon-dioxide scrubbers were
required to provide CO
2
-free air.
To evaluate additional batteries, more battery technologies were integrated in Astra Impuls
vehicles, including nickel-metal hydride batteries from Varta and Ovonics (the same
module that was used in the EV1), sodium-sulfur batteries from Silent Power, and lead-
acid batteries from Delco Remy.
The positive feedback from test drivers of the Opel vehicles led to plans to manufacture
electric vehicles, but range, cycle life, and pricing continued to present challenges.
Batteries were developed that could provide the energy for a range greater than 100 km
and cycle capability greater than 1,000 – to enable more than 100,000 kilometers of
vehicle lifetime driving distance. However, the cost of the batteries hindered the vehicles
from market introduction.
The limitation of the battery technology sparked the development of electric vehicles with
on-board generation of electricity from alternative energy carriers. In the early 1990s,
General Motors began to develop hydrogen proton-exchange membrane, or polymer-
electrolyte membrane (PEM), fuel cells. Along with these technologies, reformers for
methanol and gasoline were developed. The first vehicle with a PEM fuel cell and
methanol reformer was demonstrated in the Opel Zafira in 1998. The first “HydroGen1”
was presented in May 2000 and was used as a lead vehicle for the Marathon race at the
Sydney Olympics in September 2000. The vehicle had a liquid-hydrogen storage system
and was equipped with a 7-kWh Zebra battery.
HydroGen3, a pure fuel cell vehicle also based on the Opel Zafira, was produced in small
volume and served as a development vehicle beginning in fall 2002. In two variants it used
either compressed or liquefied hydrogen storage systems and set several fuel cell vehicle
records.
Figure 4 – GM AUTOnomy (2002), GM Hy-wire (2003), and Chevrolet Sequel (2005) fuel
cell concepts.
Bild 4 – GM AUTOnomy (2002), GM Hy-wire (2003) und Chevrolet Sequel (2005)
Brennstoffzellen-Konzeptfahrzeuge.
The GM Autonomy show car, Hy-wire experimental car, and Chevrolet Sequel test vehicle
revealed a new design concept – a platform containing a fuel cell, wheel hub motors, 700-
33. Internationales Wiener Motorensymposium 2012
bar high-pressure hydrogen vessels, and by-wire technology. The Hy-wire and Sequel
were demonstrated around the world.
These were followed by the Chevrolet Equinox/Opel HydroGen4 fuel cell vehicles. These
vehicles use batteries to store energy during regenerative braking and to help manage
dynamic energy requirements during driving. Over 110 vehicles were built for GM’s Project
Driveway, which began in 2007. These vehicles have operated successfully in six
countries through five winters, accumulated over 3.8 million km with over 6,000 drivers,
logged over 25,000 hydrogen refueling events, consumed 53,000 kg of hydrogen, and
gathered real-world experience with retail and fleet customers.
At the North American International Auto Show in Detroit in 2007, GM presented the
Chevrolet Volt concept. Two propulsion systems sharing common electric drive and
architecture were unveiled. The extended-range electric vehicle (EREV) featured a 16-
kWh battery system and 110-kW electric drive, plus a 55-kW generator driven by an
internal combustion engine. The fuel cell propulsion system consisted of a 55-kW battery
and a 65-kW fuel cell system, providing propulsion power of 120 kW.
Figure 5 – In 2011, the Opel Meriva-based “MeRegioMobil” vehicle [7], left, was the first
BEV to demonstrate vehicle-to-grid energy exchange. GM has also announced that
Chevrolet will produce an all-electric version of its Spark mini car, right, in 2013 for
selected U.S. and global markets, including California.
Bild 5 – 2011 demonstrierte das MeRegioMobil-Fahrzeug [7], basierend auf dem Opel
Meriva, links, als erstes BEV das Rückspeisen von Strom vom Fahrzeug ins Netz. GM hat
den Produktionsstart des batterieelektrischen Chevrolet Spark, rechts, für 2013 in
ausgewählten U.S. und globalen Märkten angekündigt. Das schließt insbesondere
Kalifornien mit ein.
The EREV concept initiated a product development program leading to the Chevrolet Volt,
introduced to the market in North America in November 2010, and the Opel Ampera,
introduced in Europe in December 2011. The Voltec propulsion system used in these
vehicles delivers 111 kW, primarily supplied by a 288-cell, 16-kWh lithium-ion battery
system. At low state-of-charge, a 55-kW generator powered by a 1.4-liter four-cylinder
internal combustion engine delivers energy to keep the state-of-charge constant. The
battery also provides power for acceleration and recovers energy during braking. Thus, the
vehicle can travel 40-80 km on stored battery energy and, in combination with the 35- liter
gasoline tank, up to 500 km in total. As will be discussed later, customers drive about two-
thirds of the time in electric vehicle mode and one-third in extended-range mode. Thus, the
EREV can be used as an owner’s primary vehicle due to its long range and simple
33. Internationales Wiener Motorensymposium 2012
refueling, but is also a very effective instrument for the substitution of oil-based energy for
other fuels, preferably renewable energy sources.
Today, battery-electric vehicles are starting to become an integral part of personal mobility
solutions (Figure 5).
2. Motivation for Vehicle Electrification – Past, Present, and Future
[1-6] The motivation for electrification has changed over time, as shown in Table 1. From
1890 to 1920, its benefits included ease of use and control, comfort, and lack of a gasoline
infrastructure. The efforts in the 1970s were driven by the oil embargo and price volatility.
In the 1980s, the key influence was reducing emissions to fight air pollution. Today, the
rapid increase in the number and usage of vehicles worldwide demands a greater diversity
in energy sources for the automobile. At the same time, the march toward zero tailpipe
emissions continues, further driving electrification. Hybrid-electric vehicles help to reduce
the consumption of petroleum. Fuel cell-electric, battery-electric, and extended-range
electric vehicles promise to be an effective measure to ultimately reduce dependence on
petroleum.
Era
Motivation
Before
1900
Power of the electric motor
1900
-
1915
Comfort: easy to start and control
1960s
The drive, as President John F. Kennedy defined it, to “land a man on
the moon and return him safely to the earth”
1970s
Oil embargo and emissions regulation
1980s
Exploration of technology synergies; idea of “sustainable transportation”
1990s
Reduction in local emissions, e.g., California ZEV mandate.
The logical progression to more stringent emission regulations (BEV,
FCEV). Reduce energy and resource consumption (Hybrid HEV).
2000s
Energy diversity (electricity, hydrogen, renewable sources).
Efficiency improvements through hybridization. Advances in motors and
electronics enable design of new vehicle and propulsion architectures
(e.g., GM Autonomy, HyWire, and Chevrolet Sequel).
2010s
CO
2
and CAFE regulations: Improve efficiency and use less carbon-
based energy sources. Long-term petroleum price uncertainty drives
energy diversity.
2020s and
beyond
Individual mobility in a highly populated world with limited resources.
New technologies enable innovative, connected vehicle concepts.
Table 1 – Motivation for vehicle electrification in the various eras, pre-1900 to today and
beyond.
Tabelle 1 – Motivation für die Fahrzeugelektrifizierung zu verschiedenen Zeiten, vom
Ausgang des 19. Jahrhunderts bis heute und in der Zukunft.
Technology is an enabler to make the electrified vehicle attractive to the consumer. In the
early 1900s, electric propulsion outperformed internal combustion engines, but the electric
starter, ignition systems, and readily available gasoline with its high energy density
available from a growing distribution infrastructure, gave internal engines an advantage. In
the 1960s, electric vehicles got another boost with the advance of aerospace technology
and President John F. Kennedy’s goal to “land a man on the moon and return him safely to
earth” within the decade.
33. Internationales Wiener Motorensymposium 2012
In the 1990s, power electronics and high power density electric motors made the
performance of new electric vehicles competitive with ICE vehicles again. In the 2000s, a
range of new vehicle, electronics, computer, and communications technologies enabled
new propulsion and vehicle design and architecture concepts. In the future, the growth of
renewable energy sources will drive an enhanced smart energy network encompassing
electricity and hydrogen technology.
However, further development of range-extender and fuel cell technology is necessary in
parallel with improvement of batteries because the energy capacity of the battery and,
therefore, the vehicle range remain limiting factors to pure battery-electric vehicles. When
we take the different vehicle system efficiencies into account, driving a distance of 500 km
requires 33 kg of diesel fuel (43 kg on a system basis, including the tank) compared to a
lithium-ion battery at 540 kg for the cells (830 kg for the system). (See Figure 6.) Thus, for
equal range, the mass of a lithium-ion battery is about 20 times that of a diesel fuel
system. Refueling of a diesel tank also takes only two-to-three minutes, while today’s fast
charging still requires 30 minutes to deliver 13 kWh using a 40-kW, high-power electric
charger, although this reduces battery life. In addition, charging at 40 kW could have a
significant impact on the grid. Hydrogen fuel cell storage systems have a mass of about
125 kg and can be refilled within three-to-five minutes, providing another EV option if quick
refueling and longer driving range are required.
Figure 6 – Weight and volume of energy storage systems for a 500-km vehicle range.
Bild 6 – Gewicht und Volumen des Energiespeichersystems für eine Reichweite von
500 km.
33. Internationales Wiener Motorensymposium 2012
3. Technology Roadmap for Batteries, Electric Motors, Power
Electronics, Fuel Cell Systems, and Hydrogen Storage
3.1 Batteries
[4-6] The long-used lead-acid (PbPbO2) batteries have been optimized (e.g.
maintenance-free or advanced glass matt for Stop-Start applications). They keep their
strong market position as the SLI (Starter-Lighting-Ignition) 12V battery, due to low-cost,
high-volume production, and established recycling processes.
Nickel-metal hydride (NiMH) batteries are used in hybrid-electric vehicle applications.
When operated with only small state-of-charge swings, they offer good durability.
However, the 1.2V cell voltage requires a high cell count to drive higher-voltage systems.
The market is dominated by only a few suppliers and specific cost for the high-power
battery (600 W/kg, 30 Wh/kg) is rather high. The systems also require tight tolerances, as
charge equalization, or balancing, is normally not part of the system design.
High-temperature systems such as sodium-sulfur (NaS) and sodium-nickel chloride
(NaNiCl) offer good specific energy (90 Wh/kg), but due to high internal resistance do not
provide sufficient power for modern automotive requirements. The drawback is energy
consumption to keep the temperature high during longer parking periods; this requires
plugging in when the vehicle is parked longer than 24 hours.
Invented in the 1970s and 1980s, lithium-ion (Li-Ion) batteries first were applied to
consumer applications e.g., mobile phones, laptop computers, and power tools. Many
manufacturers optimized the production process. For automotive applications, longer
battery calendar life and more charge/discharge cycles are required.
Figure 7 – The power density of HEV and EREV batteries increased significantly
compared to EV batteries in the 1990s.
Bild 7 – Die Leistungsdichte von HEV- und EREV-Batterien hat seit 2000 signifikant
zugenommen.
33. Internationales Wiener Motorensymposium 2012
Figure 8 – Specific Energy and Specific Power of GM EV, HEV, and EREV battery
systems used from 1990 to 2012.
Bild 8 – Spezifische Energie und spezifische Leistung von GM EV-, HEV- und EREV-
Batteriesystemen zwischen 1990 und 2012.
Several cathode and anode chemistries have been developed and many developers and
manufacturers have created various solutions. Small cells are offered in cylindrical and
pouch (rectangular) format, large cells (>10 Ah) are mainly made in a prismatic pouch or
metal-can form. The cell voltage is dependent on the chosen cathode and anode material
and typical nominal voltages range from 3.6-3.8V, with an operation range from 4.2V (high
state-of-charge) down to 3V (low state-of-charge). This enables the design of battery
systems with higher voltage and a smaller number of cells.
Mass and Cost Contribution
of Lithium-Ion Cells
Cathode and Anode
Material Effect
Cathode material
Cell Voltage
Anode material Specific energy (Wh/kg)
Electrolyte Energy density (Wh/liter)
Separator Cycle and calendar life
Current collector Abuse tolerance
Cell housing
Cost
Both cell design and the electrolyte impact specific power (W/kg) and cost.
33. Internationales Wiener Motorensymposium 2012
Cathode
Material
Acronym
Cathode
Material full
Application Pro Con
LCO Lithium Cobalt
Oxide
Notebook,
Phone
Power Cost of cobalt
(high content),
abuse tolerance
LNMC Lithium Nickel
Manganese
Cobalt
EREV, EV Life Nickel and cobalt
cost
LMO Lithium
Manganes Oxide
EREV, EV Low material
cost,
Safety
Life at temp
>40°C
NCA Lithium Nickel
Cobalt
Aluminium
HEV,
Notebook,
Phone,
Power,
cycle life,
calender life
Cost of nickel
and cobalt (high
content), limited
abuse tolerance
LFP Lithium Iron
Phosphate,
"Olivine"
Power tools,
EV
Low material
cost,
Safety
Lower energy
density
Table 2 – Commercially used cathode materials.
Tabelle 2 – Kommerziell angewandte Kathodenmaterialien.
The future will see the continued evolution of lithium-ion battery cell cost due to better
manufacturing processes, which will lead to higher yields resulting from better process
control. Improvement of known “lower-cost” cathode materials and methods such as
particle coating will also facilitate lower cost and longer cell life.
The future for battery systems will also see cost reductions due to higher production
volumes, reduced part count, optimized cell controllers, and application of the learnings
from production of the first-generation units.
Figure 9 – Battery progress, past and future.
Bild 9 – Fortschritte in der Batterietechnologie.
33. Internationales Wiener Motorensymposium 2012
Concepts that promise significantly higher energy density – such as silicon anodes,
lithium-sulfur cells or lithium-air batteries – have just entered the research stage; it will take
many years before they are qualified for use in a vehicle program.
Nevertheless, the further development of the battery technology will result in less
expensive batteries with higher energy density and greater durability. For the simultaneous
improvement in cost and energy density, a factor of one-point-five to two seems
reasonable in the future. Whether this is biased toward vehicle cost or vehicle range
depends on the chosen vehicle architecture.
3.2 Motors
Direct-current (DC) motors, which were used up to the early 1990s, were replaced by
alternating-current (AC) induction motors and soon by permanent-magnet (PM), excited
synchronous motors. Development of rare-earth magnets in the 1980s, led by GM’s
Magnequench, enabled compact motors with high torque and efficiency. In recent years,
prices for raw materials such as neodymium have been very volatile due to increasing
demand and a limited production base, which is concentrated in China. Future optimization
thus must balance cost, mass, volume, and efficiency. This makes motor concepts such as
the separately excited synchronous motor or the AC induction machine very attractive.
In addition, the permanent-magnet synchronous motor has a future at reduced cost as
production volumes grow and competing manufacturers enter the business. Designs will
also be optimized for manufacturing, since PM synchronous motors allow torque-rich,
compact designs and integration of small motors into transmissions. Examples include
GM’s e-Assist™ light electrification system or the motors in its extended-range electric
vehicles and hybrid-electric vehicles.
Large motors for electric vehicles could also be designed as AC induction motor and
synchronous motor.
Figure 10 – Electric motor and power electronics progress, past and future.
Bild 10 – Fortschritte bei Elektromotoren und Leistungselektronik.
Going forward, the focus for the electric motor is on cost reductions while keeping
efficiency high and further reducing mass.
33. Internationales Wiener Motorensymposium 2012
3.3 Power Electronics
The thyristor had been the semiconductor used to control the rotor current in DC
machines, using a transistor for the small rotor current.
Three-phase AC motors require six “switches,” which should operate with low conduction
losses and high frequencies.
The first MosFETs allowed efficient control of AC machines, but required a high number of
components, leading to reduced reliability. The development of the insulated-gate bipolar
transistor (IGBT) in the 1990s allowed high switching frequencies for low noise and high
propulsion efficiency. Integrated modules contain 6 IGBTs and diodes in one component.
Inverters today are also smaller, lighter, and cheaper. The cost will be further reduced by
higher production volumes, improved IGBT modules, and optimized inverter design.
Longer-term improvements will be based on new semiconductor materials. Power inverter
efficiency, size, and mass have progressed greatly in the last two decades and will further
improve slightly in the future.
3.4 Fuel Cell Systems
In the late 1990s, the polymer-electrolyte membrane (PEM) fuel cell had been developed
with higher power density to power electric drives in light-duty vehicles. The cost for fuel
cell stacks was reduced significantly due to improved materials and designs. With specific
power [kW/kg] and power density [kW/l] increases, fuel cell propulsion systems became
more cost-competitive. The durability of the fuel cell systems has also been increased
substantially.
The next-generations fuel cell systems will require reduced catalyst loading, lower-cost
membranes, and improved manufacturing processes. Scaling up production will enable
significant cost reduction.
Figure 11 – Evolution of the fuel cell system.
Bild 11 – Evolution der Brennstoffzellensysteme.
33. Internationales Wiener Motorensymposium 2012
3.5 Hydrogen Storage Systems
Currently, high-pressure hydrogen storage systems show better performance than liquid
hydrogen storage and hydride storage. Today’s systems are 70 MPa (700-bar) pressure
vessels designed using carbon fiber and a plastic or aluminum liner. Since an automotive
system must be able to store at least 4 kg of hydrogen to achieve customer-acceptable
range in a compact car, the cost of the hydrogen storage system is driven by material
(carbon fiber) and processing. Higher-volume production and improved manufacturing
processes will decrease cost significantly and refined designs will slightly reduce the mass
of the system.
The progress that has been made over the last 15 years in terms of the cost, mass,
reliability, and durability of electric-drive systems has been tremendous. It has enabled
market introduction of a range of electrified systems, from e-Assist™ mild hybrids to
extended-range electric vehicles and full battery-electric vehicles. EREVs, a category of
vehicle that GM created, set the standard for today’s electric vehicle technology because
they are the first electric vehicles where customers do not have to worry about being
stranded by a depleted battery. Once the all-electric driving range is exhausted, a
gasoline-powered generator can power the electric motor for hundreds of additional
kilometers of highway driving. The trend to lower cost will continue and in future years we
will see increased market share of partly to highly electrified propulsion systems and even
fuel cell-electric vehicles across all vehicle classes.
4. Energy Sources and Supply Chain for Mobility
The global transport sector uses a staggering 2.1 billion tonnes of oil every year (45 million
barrels per day) [15], more than half of total oil use. Maintaining the oil supply chain and
creating new transport fuel supply chains are enormous tasks. We will: (1) review history
and projections of transport energy sources, (2) assess grid stability and its potential
impact on automotive fuels, and (3) evaluate the fuel lifecycle from resource to vehicle
usage.
4.1 Liquid Fuel History and Projections
The transport sector in general, and light-duty transportation specifically, have developed
almost exclusively around the use of gasoline and diesel produced from crude oil
(conventional and unconventional) and natural gas liquids. The IEA [15] historical data and
projections of total world liquids fuel supply is shown in Figure 12. From 1990 until today,
world liquids demand increased at a rate of about 1% annually. Although the growth in
total liquids supply slows to a rate of about 0.6% annually, transportation liquids demand is
expected to continue increasing at about 1% per year, driven largely by increased
transportation in the developing world.
Figure 12 shows that the growth in liquid fuels will be provided by biofuels, unconventional
oil, and natural gas liquids, as crude oil supplies remain flat. However, flat supply of crude
oil does not mean continuing only to produce from currently producing fields. Supply from
currently producing fields will decline roughly 70% by 2035, leaving a gap (shown within
the dotted red line) to be filled by fields yet to be developed and fields yet to be found.
33. Internationales Wiener Motorensymposium 2012
Figure 12 – World liquid fuels supply showing investment required to maintain crude oil
production; source: [15].
Bild 12 – Weltweite Versorgung mit flüssigen Energieträgern verdeutlicht den
Investitionsbedarf um die Produktion zu sichern; Quelle: [15].
Most experts do not anticipate the world running out of oil (estimated 5,500 billion barrels
of recoverable resources). However, the amount of capital required, timing of investment
of that capital, and carbon footprint of unconventional sources could be issues. The inset
in Figure 12 projects that $10 trillion of cumulative investment will be required to maintain
conventional oil supply and increase unconventional oil supply from 2011 through 2035.
Nearly $9 trillion of that investment is required for exploration, well development, and
equipment for transport of oil from wells to refineries. If future oil demand and supply were
entirely predictable and there was no time lag between investment and production, timely
investments would be expected to match supply with demand.
4.2 Electricity and Hydrogen
Electricity is produced from a diverse set of resources throughout the world. The mix of
resources varies regionally, as shown in Figure 13. Electricity from coal comprises about
20%, 50% and 80% of electricity in the EU, U.S., and China, respectively.
Figure 13 – Current mix of resources for electricity production [13,14,15].
Bild 13 – Aktueller Energiemix bei der Stromerzeugung [13,14,15].
Non-fossil resources, including nuclear, hydro, and renewables, have the greatest share in
the EU and smallest share in China. Shares of non-fossil resources are expected to
increase. In its New Policies Scenario, IEA [15] projects world annual generation increases
of 7% for biomass, 9% for wind, 6% for geothermal, and 15% for solar. Shares of non-
hydro renewables in 2035 are projected to be 15% globally and over 30% in the EU.
US China
EU
33. Internationales Wiener Motorensymposium 2012
Infrastructure to generate and distribute electricity is well-developed in most regions.
Addition of vehicle charging is not expected to substantially impact generation or
transmission of electricity in the near future, because transportation demand is expected
[15] to be a small share of total generation. Impact of vehicle charging on the distribution
requires more study. What is required at the point of charging is a compatible plug socket
and an electric vehicle supply equipment (EVSE) interface to the vehicle. Charging
interfaces have been established [16] for Level 1 (120V/1.4 kW), Level 2 (240V/3-19kW),
and are being developed for DC “fast” charging. The high electrical-power demand of fast
charging might drive significant additional investment.
Although technology for hydrogen production is well known, infrastructure for distribution
and vehicle refueling is small, consistent with the small number of hydrogen-fueled
demonstration vehicles available. Hydrogen can be produced from electricity by
electrolysis or by catalytic reforming of natural gas, other fossil fuels, and biomass. Large-
scale production of hydrogen from natural gas by catalytic reforming uses well-developed
technology and is employed by petroleum refineries. Electrolysis of hydrogen is also well-
developed, but used at moderate scale. Vehicle refueling stations could produce hydrogen
onsite by electrolysis or small-scale reformers, or hydrogen could be distributed from large
plants to refueling stations by pipeline or truck. When available and used at large scale,
hydrogen costs are expected to be competitive with petroleum fuels. What is expected to
be a challenge, however, is the transition between essentially zero hydrogen refueling
stations to a density sufficient to meet the expectations of customers of hydrogen-fueled
vehicles. Most favor addressing the transition issue by regional introduction of vehicles
and fuel. Examples of cities with hydrogen refueling stations and plans for more are Los
Angeles, San Francisco, New York City, Tokyo, Seoul, Shanghai, Hamburg, Frankfurt,
Stuttgart, and Berlin.
4.3 Grid Stability, Large-Scale Renewable Energy Storage, and the Automobile
In this section, the challenges in Europe arising from the integration of renewable energy
sources like wind and solar power into the overall energy system and the corresponding
importance and usage of green energy carriers for automotive applications are discussed.
The challenge of utmost importance for any country in the industrialized world is to ensure
a safe and reliable power supply. Germany is used as a specific example since it is the
biggest economy of the European Union and since it has committed to the most
aggressive targets for the replacement of fossil and nuclear technologies.
To maintain a stable, high-quality electric grid (but also for battery technology reasons), EV
charging times of at least one to several hours or even longer periods and the utilization of
a sophisticated smart-charging communication protocol (or even a bi-directional energy
flow, such as what was pioneered using an Opel Meriva BEV within the MeRegioMobil
project [7]) will eventually be required to avoid large load swings due to vehicle charging.
One million EVs charging (from a total German car park of 40 million vehicles) at a single
point in time in the early morning or the evening would cause a power demand of 3.5 GW
when using standard German home sockets and installations. To put this into perspective,
a single large-scale baseload power station (nuclear or coal-fired) provides typically only
about 1 GW to the grid. Since it will take some time to build up to one million EVs,
however, grid operators will be able to react to automotive market sales trends and, in the
meantime, establish smart-charging protocols to manage these growing loads.
33. Internationales Wiener Motorensymposium 2012
Nevertheless, for plug-in vehicles, there exists a strong interdependency between two
normally distinct activities, namely “parking” and “refueling.” This interdependency is not
the case for FCEVs, where a typical refueling process takes only 3-5 minutes. Additionally,
hydrogen offers a different and very important advantage over stored electricity because of
hydrogen’s higher energy density (see Figure 6). Hydrogen, methane, or other “designer
chemical energy carriers” could serve as the ideal partner for the intermediate storage of
fluctuating, renewable energies. In doing so, excess amounts of sustainable energy
sources, such as solar and wind power, can be made available not only for stationary but
also for automotive applications.
Let us consider, for example, the North German electric power grid, the so-called ‘‘TenneT
Regelzone’’. In October 2008, the power fed into the grid by wind turbines fluctuated –
sometimes within a few hours, sometimes within days – between a maximum of
approximately 8000 MW and virtually zero (see Figure 14).
Figure 14 – Fluctuating wind energy in October 2008 in the grid operated by TenneT
compared to biggest German pumped hydro storage Goldisthal (a Vattenfall installation
in the state of Thuringia) [10].
Bild 14 – Schwankung der Windenergie im Oktober 2008 im Netz von TenneT im
Vergleich zur Kapazität des größten deutschen Pumpspeicherwerk Goldisthal (Fa.
Vattenfall, Thüringen) [10].
An excess amount of available wind power, for example, at several points since 2009
dramatic caused effects on the energy markets, such as significantly negative prices of up
to minus 25 ct/kWh for electric energy at the European Energy Exchange (EEX).
According to the German wind energy industry association, in 2010 the nationwide total
installed wind power capacity had risen to 27,215 MW, a 5.6% increase over the
respective 2009 value [9]. In the first 9 months of 2011, wind power contributed already on
average about 8% (solar power accounts for 3%) of the German gross electricity
production [9]. But not only these short-term fluctuations need to be covered; wind power
also shows significant seasonal dependencies in its electric generation (see figure 15a).
During the winter half-year in Germany, typically 3.5 TWh of wind energy was generated
per month (2003 to 2009 mean), while during summer this number drops on average to
values below 2 TWh [9].
33. Internationales Wiener Motorensymposium 2012
Figure 15 – a) Wind electricity generation in Germany, 2011, seasonal effects and the
winter storms of December 2011; b)Share of electricity produced from renewable energy
sources in Germany, statistical data through 2011 and the “Energiekonzept” targets of the
German national government [9].
Bild 15 – a) Strom aus Windenergie in Deutschland, 2011, Jahreszeiteneffekte und die
Stürme im Dezember 2011; b) Anteil der Stromerzeugung aus erneuerbaren Energie-
quellen in Deutschland; statistische Daten bis 2011 und Ziele des Energiekonzepts der
deutschen Bundesregierung [9].
It will become even more important and urgent to solve these challenges when the already
approved or planned off-shore wind farms (e.g., in the North Sea) come online later this
decade. This is of particular importance after the Fukushima accident of 2011 when the
German government decided to phase out the nuclear power stations providing a major
share of the country’s base load and, as compensation, to increase the share of fluctuating
renewable energy dramatically (see Figure 15b [9]). Furthermore, these energy sources
currently feature low annual utilization numbers (solar: 900h, wind: 1500h; 1 year =
8760h). An additional issue for grid operators arises from the fact that the typical wind
power installations are located in the sparsely populated coastal areas close to the North
and Baltic Seas, whereas the population and industry centers are to be found mainly in the
south, resulting in a very significant energy transmission challenge. The current German
grid infrastructure is already operated at its limit.
Hence, it is clear that it would be extremely helpful to ‘‘buffer’’ excess energy in
intermediate storage systems to handle these supply fluctuations, i.e., to absorb energy
during a certain time period from the grid or, vice versa, to provide energy back to the grid
in case of a high market demand. [8] Today, this ‘‘buffer’’ is realized as pumped hydro
storage facilities (e.g., the largest facility in Germany, Goldisthal [10], offers a maximum
storage capacity of 8000 MWh).
If hydrogen is used as a storage medium instead, up to 600,000 MWh of energy could be
stored in a two million cubic meter salt cavern. Unlike conventional technology, hydrogen
therefore offers not only buffer storage for short time periods ranging from a few minutes to
33. Internationales Wiener Motorensymposium 2012
hours, but such a large-scale hydrogen storage facility could also absorb the excess wind
energy of several days. The stored gas could eventually be either converted back into
electrical energy or could simply be used as a fuel for hydrogen vehicles. By contrast,
even large fleets of pure battery EVs are not able to provide a competitive energy storage
dimension: if, for example, 5 kWh of the usable energy content of an EV battery (for
operating lifetime and customer ease-of-use considerations, 10% of the total nominal
energy content should not be exceeded) could be subscribed to and used by the electric
utility, just to replace the pumped hydro store of Goldisthal, 1.6 million EVs would be
needed. Also, other large-scale stationary battery systems (based, e.g., on Na-sulfur or
lithium technology) are by far not able to provide energy storage dimensions comparable
to a hydrogen-based system. [8]
Since the setup of a viable and sufficiently dense hydrogen infrastructure in the short term
is considered a significant challenge by virtually all major stakeholders in both industry and
academia, concepts have been presented over recent years to utilize synthetic natural gas
as a chemical energy carrier (in particular by Specht, Sterner et al. [11]). In this concept,
fluctuating renewable energy (again especially wind energy) is used for the electrolysis of
water. The produced hydrogen and CO
2
(taken from a CO
2
-producing industrial or biogas
compound) react via the well-known Sabatier process to form methane (in this case, also
known as synthetic methane):
4 H
2
+ CO
2
à CH
4
+ 2 H
2
O(g)
Typically, Ni-based catalysts are used and according to Specht, Sterner et al, the reaction
takes place in a fixed-bed reactor at temperatures between 250-500°C at a pressure of
circa 0.8 MPa. The produced process gas is not pure methane; it consists roughly of 87%
CH
4
, 6% CO
2
, and 7% H
2
. This synthetic natural gas (SNG) product could be fed into the
existing natural gas pipeline and storage network in many industrialized countries. By
doing so, additional energy storage capacities of the TWh dimensions could be reached.
Unfortunately, although the Sabatier reaction is highly exothermal, the conversion step
from hydrogen to methane is not for free. The Sabatier chemical equation directly states –
based on mass flows – that 8 kg of hydrogen (corresponding to an FCEV range of 650 km)
would be needed to produce 16 kg of methane (equivalent to an ICE range of 250 km).
Furthermore, the energy usage also has to be assessed. Under ideal conditions, a
conversion efficiency for the methanization of maximum 80% may be reached. For
detailed numbers of different paths and usage, see Table 3.
33. Internationales Wiener Motorensymposium 2012
Path
Efficiency
Boundary Condition
Electricity
-
to
-
Gas
Electricity à Hydrogen 57 - 73%
Compression up to 8 MPa (pipeline
pressure)
Electricity à Methane (SNG) 50 - 64%
Compression up to 8 MPa (pipeline
pressure)
Electricity à Hydrogen 64 - 77% Without compression
Electricity à Methane (SNG) 51 - 65% Without compression
Electricity
-
to
-
Gas
-
to
-
Electricity
Electricity à Hydrogen à
Electricity
34 - 44%
8 MPa compression, 60%
re-conversion efficiency
Electricity à SNG à Electricity 30 - 38%
8 MPa compression, 60%
re-conversion efficiency
Table 3 – Large-scale energy storage: Efficiency of various conversion paths [11].
SNG: Synthetic Natural Gas.
Tabelle 3 – Großtechnische Energiespeicherung: Effizienz verschiedener
Umwandlungsketten [11]. SNG: Synthetisch erzeugtes Methangas.
The basic idea behind the SNG concept – to use the conversion of electric energy into
chemical energy carriers and the existing natural gas infrastructure for the integration of
renewable energy into the energy system of an industrialized country – is definitely worth
considering. But evaluating Table 3, it becomes clear that the gas storage should be
carried out at the step in the process chain that provides the greatest advantage in terms
of conversion efficiency. The SNG process builds on top of the hydrogen production step
and leads to a considerably higher technology complexity and higher investment cost.
Energy-wise, 100 GWh of electrical energy translates via the Sabatier process to 58 GWh
of SNG compared to 71 GWh of hydrogen. The storage and direct use of the electrolysis
hydrogen, therefore, obviously has to be preferred from an energy use point of view,
especially since it is also possible to feed hydrogen directly into the existing natural gas
grid up to a concentration of 5%.
Unfortunately, the SNG picture gets even less attractive when vehicle applications are
considered. Due to the comparatively low efficiency of the CNG internal combustion
engine and the occurring Well-to-Wheel losses, only about 10% of the primary wind
energy would be available at the wheels of a natural gas vehicle. If the process would be
stopped at the hydrogen stage and considering a fuel cell-electric vehicle (FCEV efficiency
about two times greater than for ICE vehicles [8] [12]), about 30% of the primary energy
could be used for transportation purposes at the wheels. In addition, the direct use of the
hydrogen also has the advantage of being locally emission-free. In contrast, in the case of
an SNG-powered vehicle, NO
x
and CO
2
would be locally emitted by the car.
At present, several pioneer projects in Germany testing the storage of wind energy in the
form of hydrogen are already ongoing. Additionally, in December 2011, the consortium
“Performing Energy” was created to commercialize wind-hydrogen technology. This
organization consists of several academic partners, three German states, and major
industrial companies like Siemens, Linde, Total, and Vattenfall. The consortium intends to
provide a strong link to the transportation sector by interfacing with the German “Clean
Energy Partnership” hydrogen vehicle program.
33. Internationales Wiener Motorensymposium 2012
It is highly advantageous, especially for transportation applications, to keep the number of
energy conversion steps as low as possible. This is enabled by using batteries as an
electrical energy carrier and hydrogen as a chemical energy carrier and employing them in
various types of electric vehicles.
To enable and commercialize such large-scale energy storage technologies, which are
essential to reach the highly ambitious German renewable energy targets of the
“Energiekonzept” [9], a technology-neutral incentive scheme for load-leveling applications
would be required.
4.4 Fuel Lifecycle
If gasoline were the only fuel used, vehicle efficiency alone would be a good tool for
assessing the environmental footprint of propulsion options. Adding biofuels, compressed
natural gas, hydrogen, and grid electricity to the mix requires analysis of the full fuel
lifecycle, including production and delivery of the required resource, conversion of
resource to fuel, and delivery of fuel to the vehicle. Another term used for fuel lifecycle
analysis is “Well-to-Wheels” (WTW).
There have been a vast number of studies of fuel lifecycle of future fuel/propulsion options.
In Europe, the most comprehensive and widely used study [14] is that jointly conducted by
the European Commission Joint Research Center, CONCAWE (oil industry consortium),
and ACEA (auto industry consortium). In the U.S., the most widely used tool for fuel
lifecycle is GREET [13], developed by the Department of Energy’s Argonne National
Laboratory.
To compare greenhouse gas (GHG) emissions across the various fuel/propulsion options,
we used a GM-proprietary vehicle simulation tool to assess the U.S. on-road vehicle
efficiency of a C-segment passenger car. Combining the GM vehicle efficiency results with
the Well-to-Tank assessment (gCO
2
e/MJ of fuel) from the Joint Research Centre [14]
provide the results shown in Figure 16. Fuel lifecycle GHG for conventional diesel and
CNG were within the range of conventional gasoline and gasoline strong hybrids. Biofuels
and biomethane blends could further reduce lifecycle GHG for these internal-combustion
engine options. The BEV, plugged into electricity with the GHG footprint of the average
mix of the EU grid, provided GHG about half that of conventional gasoline and 30% below
that of a strong gasoline hybrid. If the BEV were powered with wind electricity, fuel lifecycle
GHG would be zero. WTW GHG of the EREV, like the BEV, depends on electricity GHG
footprint, but also depends on charging and driving behavior. Figure 16 shows results for
EREV with 50%, 75%, and 100% of kilometers driven on plug electricity. Increasing the
share of kilometers on plug electricity reduces WTW GHG. For the hydrogen fuel cell,
sources of hydrogen analyzed include natural gas reforming at a central plant and onsite
electrolysis from the EU grid mix or wind electricity. The FCEV operating on hydrogen from
natural gas reforming had fuel lifecycle GHG about 35% below those of conventional
gasoline. With hydrogen from wind electricity, the low FCEV lifecycle GHG were slightly
above zero because of truck distribution and compression. However, the hydrogen fuel cell
with hydrogen produced from EU average mix electricity increased fuel lifecycle GHG
above that of conventional gasoline. Fuel lifecycle GHG were higher with the FCEV than
BEV on the same electricity mix due to energy losses in hydrogen production from
electricity.
33. Internationales Wiener Motorensymposium 2012
Figure 16 – Well-to-wheels greenhouse gas emissions for various propulsion types and
fuel sources; sources: well to tank – JEC [14], tank-to-wheels based on GM analyses for
C segment, U.S. on-road.
Bild 16 – Treibhausgasemissionen von Primärenergiequelle bis zur Nutzung für
verschiedene Antriebstechnologien und Kraftstoffe; Quellen: Vorkette – JEC [14], Tank-zu-
Rad – GM Simulation für C-Segment-Fahrzeuge, US-Realfahrzyklus.
Figure 16 shows that the electrification pathways offer the opportunity to drive
transportation toward zero fuel lifecycle greenhouse gas emissions. Reductions in GHG for
the BEV may be exaggerated, however, because its limited driving range prevents it from
being used for all trips. Trips longer than the driving range would have to be taken with
another vehicle or transport mode, and would likely increase the GHG footprint of the trip.
The EREV does not have this limitation, nor does the FCEV, as long as hydrogen refueling
is widely available. Use of 100% cellulosic biofuels, although not included in this analysis,
could also provide near-zero lifecycle GHG.
The symbols in Figure 16 also indicate the energy resources in each the fuel/propulsion
options. With the gasoline and diesel options, transportation is tied exclusively to oil and
subject to oil price volatility. With the addition of CNGVs, transportation can diversify from
its dependence on oil. The electrification options, EREV, BEV, and FCEV, provide
opportunity for increased diversification from oil.
5. Electric Vehicle Usage Experience
In recent years, a great deal of customer experience operating electric vehicles in the real
world has been gathered as part of GM’s Project Driveway fuel cell market test and from
data collected from Chevrolet Volt owners and Opel Ampera test vehicles.
33. Internationales Wiener Motorensymposium 2012
Additional data was also obtained from other earlier EV vehicles and test programs. From
1993 to 1996, during the Ruegen Field Test, ten electric Opel Impuls vehicles accumulated
250,000 km. One result of this study was that customers reported a favorable impression
of battery technology and its potential to help reduce petroleum consumption.
The Impact Preview test program in the early 1990s and, beginning in 1996, the lease of
production GM EV1 electric vehicles in Arizona, California, and New York provided a
wealth of customer feedback and significant lessons learned for engineers working on the
technology. They designed the vehicle to be very efficient and, therefore, to achieve a
reasonable range; customers responded by competing to drive more efficiently and with
minimum energy.
Since 2007, 119 Chevrolet Equinox and Opel HydroGen4 vehicles have been tested as
part of the Project Driveway market test. These vehicles have operated successfully in six
countries through five winters, accumulated 3.8 million km with over 6,000 drivers, logged
over 25,000 hydrogen refueling events, consumed 53,000 kg of hydrogen, and gathered
real-world experience with retail and fleet customers. During the program, 20 vehicle
collisions occurred – two were total losses – with no hydrogen lost. The data recorded is
being used to support the design of GM’s next-generation fuel cell-electric vehicle.
The Chevrolet Volt extended-range electric vehicle allows data upload through GM’s
OnStar mobile communication system and information to the driver through the internet.
OnStar data reveals that two-thirds of all Volt miles driven were performed with electric
energy in “EV” mode. Furthermore, the average Volt customer had 30 days between and
drove almost 1500 km between gas fill-ups. On average, every vehicle is driven more than
50 km per day (20,000 km/year). For comparison, in Germany, diesel passenger cars drive
on average 18,500 km per year and passenger vehicles with gasoline engines drive
11,500 km per year. The extended-range electric vehicles – with an EV range of 56 km
based on the EPA label, or 83 km based on EU certification – allow significant
replacement of petroleum-based fuel (60% to 80%) by electricity.
Data of Opel Ampera test vehicles used by engineers over several months show that, in
this sample, 45 km per day can be driven in EV mode (see Figure 17). This is more than
the average gasoline ICE vehicle in Germany, 31 km per day. The Ampera test vehicles
were driven 72 km per day, which exceeds the average driving distance of diesel
passenger cars in Germany of 15 km per day.
Customers who have had the opportunity to drive or own an electrically driven vehicle
have been extremely positive about the driving experience, often saying they “love” their
vehicles and that they are “fun to drive.” Drivers of electric vehicles (both battery and fuel
cell) also express the thrill of electric torque, the smooth ride and handling of these
vehicles, and the quietness of the vehicle. Experience with the EV1 influenced the
development of the Chevrolet Volt and Opel Ampera. Data show that a high percentage of
EV driving is achieved with an EREV. Real-world energy consumption matches the EPA
label in the DoE INL project data and underlines the potential to replace petroleum. Project
Driveway has demonstrated the day-to-day potential of fuel cell vehicles.
33. Internationales Wiener Motorensymposium 2012
Figure 17– Ampera test vehicles driven by engineers drove 63% in electric vehicle mode
despite the high distance of average 72 km/day exceeding the average daily driving
distance in Germany.
Bild 17 – Ampera-Versuchsfahrzeuge von Ingenieuren im Alltag genutzt erreichen 63% im
elektrischen Modus obwohl die durchschnittliche tägliche Fahrleistung in Deutschland
erheblich übertroffen wird.
6. The Vehicle Application Map
The electrification of the vehicle is a necessity to achieve the agreed targets for fleet
emissions of carbon dioxide. Further efficiency improvements in the internal combustion
engine are still possible, but that improvement is limited and cannot achieve the
environmental friendliness an electric drive can provide.
The environmental criteria are important for customer acceptance of a new vehicle
propulsion system technology. Equally important in terms of customer acceptance is that a
new technology must be able to meet the performance and utility (size and usable space)
that customers are used to and expect from currently available technology.
A third important factor influencing customer acceptance of a new propulsion technology is
cost. Here, the appropriate measure is overall cost of ownership, which includes not only
the vehicle price but also costs for fuel and maintenance.
The important question now is what the optimal level of electrification for the future vehicle
propulsion system will be, considering the listed assessment criteria of performance,
environmental compatibility, and total cost of ownership over the bandwidth of vehicle
applications?
To understand this relationship, an extensive study was conducted using expertise from a
variety of arenas available within GM. One basis for the analysis was a vehicle application
matrix, shown in Figure 18. This matrix differentiates two types of duty cycles for vehicles,
light-load vehicles and high-load vehicles, as well as five vehicle drive cycles – from stop-
and-go driving, represented by the FTP city driving schedule or the Manhattan Bus Cycle –
up to almost continuous driving, represented by the FTP highway cycle. With this
approach, a 2x5 matrix was generated and for each section of the matrix a suitable vehicle
platform with representative performance requirements was identified.
33. Internationales Wiener Motorensymposium 2012
Figure 18 – Application matrix used to assess optional propulsion systems for various duty
and drive cycles.
Bild 18 – Anwendungsmatrix zum Bewerten konkurrierender Antriebssysteme bezüglich
Last- und Fahrzyklen.
Optional propulsion systems for the various vehicle platform applications must fulfill duty
and drive cycle performance requirements in order to be considered applicable in a
specific section. Using this approach, the vehicle class-specific performance requirements
and the vehicle parameter became prerequisites instead of evaluation criteria. They are
the starting point used for the configuration of any optional propulsion system.
The propulsion systems considered in this study include a gasoline internal-combustion
engine (ICE), a diesel ICE, a compressed natural gas (CNG) ICE, a gasoline mild hybrid, a
gasoline strong hybrid, a diesel strong hybrid, an extended-range electric vehicle (EREV),
a battery-electric vehicle (BEV), and a fuel cell-electric vehicle (FCEV). For each section of
the application matrix, each optional propulsion system is configured to meet the vehicle
performance requirements.
For the purposes of the study, hydrogen was assumed to be produced by steam reforming
of natural gas. For electric energy consumption, the European grid mix was used as the
basis to determine CO
2
emissions and total energy consumption.
One example of a section-specific vehicle performance requirement is a vehicle driving
range for a specified load cycle. For the C segment (L3), a driving range of 600 km was
identified as a minimum, using the LA92 driving schedule as the reference. For a BEV, this
range requirement is not realistic, as Figure 19 illustrates. The needed battery capacity
must be increased by adding battery mass, and added battery mass leads to further
energy requirements (this relation is not considered in Figure 6). To achieve the 600 km
driving range target using a battery for a C segment vehicle (L3), the vehicle weight would
need to increase by about 290% compared to a conventional ICE vehicle.
33. Internationales Wiener Motorensymposium 2012
Figure 19 – Vehicle curb weight sensitivity to battery-electric vehicle driving range.
Bild 19 – Reichweiten-Einfluss auf das Leergewicht eines batterieelektrischen Fahrzeugs.
The drive cycle, of course, has significant impact on the necessary battery capacity per
driving range, as illustrated in Figure 19. In addition to the driving schedule the auxiliary
load for passenger comfort, like heating and cooling, is important to consider in the design
of a battery system for a BEV application. The recharge time for the battery is another
limitation in increasing the vehicle driving range. With a 3 kW recharge capability and 6
hours recharge time a driving range of 150 km (LA92 cycle) and 220 km (FTP city cycle) is
achievable.
Considering vehicle cost for this comparison, it is even more obvious that a BEV is not
able to achieve the driving range that a customer expects from a compact-class vehicle. A
BEV can only be considered for sections in which a reduced vehicle driving range of 100-
200 km is acceptable for the customer, such as a light-load vehicle for city driving only or a
city bus application. Determining the cost of ownership for such a limited-range application
must include the complete mobility needs of the customer. Therefore, higher-range
traveling must be accommodated in the total cost of ownership by adding expenses that
will be incurred for car rental and/or use of other means of transportation providing long-
distance traveling.
Although fuel cell technology has significantly higher efficiency than internal-combustion-
engine technology, thermal heat rejection by the vehicle radiator is higher with a fuel cell
vehicle. This is due to exhaust gas enthalpy, which is much lower for a fuel cell powertrain
compared to an ICE powertrain. In addition, the fuel cell is limited with a maximum coolant
temperature of about 95°C. Thus, the thermal cooling task for an FCEV is more
challenging than for conventional vehicles and therefore maximum continuous power is
limited by maximum possible vehicle radiator area (see Figure 20).
33. Internationales Wiener Motorensymposium 2012
The radiator performance is dependent on air flow, vehicle speed, radiator fan operation,
temperature difference between coolant and air, etc., but Figure 20 gives for a typical
thermal design case the bandwidth of maximum mechanical power of a FCEV for various
vehicle applications, referring to the section definition of Figure 18. This thermal restriction
is relevant in assessing a FCEV within the application map. Here, it is important to note
that this limitation is affecting continuous mechanical power only and not the peak
performance of the FCEV.
Figure 20 – Continuous mechanical vehicle power in relation to maximum available
radiator area for various FCEV applications.
Bild 20 – Kontinuierliche mechanische Leistungsabgabe als Funktion der verfügbaren
Kühlerfläche für verschiedene FCEV Anwendungen.
A second considerable restriction for FCEVs is the package space required for the
hydrogen storage system; this factor needs additional detailed analysis. Based on the
performance requirements identified for this study, however, the FCEV could be applied in
each section.
The assessment of optional propulsion technologies within the defined application map
has led to the following results: With respect to well-to-wheel CO
2
emissions, the BEV is
the preferred solution in sections L1/L2 and H1/H2, in cases where limited driving range
can be ignored. When considering total well-to-wheel energy consumption, BEV, FCEV,
and EREV technologies are very close within these sections. For sections L3 to L5 and
H3/H4, FCEV and EREV technology provide the lowest total energy consumption and the
lowest well-to-wheel CO
2
emissions compared to the other powertrain technologies
investigated.
The electrification of the vehicle powertrain offers regenerative braking and engine load
point optimization. Therefore electrification of the vehicle powertrain will increase with the
need to improve fuel economy in balance of the total cost of ownership. A prediction on the
growth rate for powertrain electrification always contains the uncertainty of cost forecast
for fuel and energy, but also for technology cost development, which is again coupled with
the production volume.
33. Internationales Wiener Motorensymposium 2012
Fuel cell and battery electric powertrains both offer in addition locally emission-free driving,
which is simply not achievable with an ICE engine and only partly achievable with a PHEV
or an EREV. Figure 21 shows how limited zero-emission driving compares to customer
expectations and the effort to install battery capacity. Fuel cell technology offers a solution
that enables emission-free driving while achieving customer expectations for vehicle
driving range and moderate performance requirements.
Figure 21 – Electric energy storage capacity of various vehicle electrification schemes and
the resulting impact on zero-emission driving range.
Bild 21 – Elektrische Energiespeicherkapazität verschiedener Fahrzeugkonzepte und der
resultierende Einfluß auf die erreichbare Null-Emission Fahrstrecke.
In the future, both electric power and hydrogen production paths will change as a result of
the increasing use of wind and solar energy, which will further reduce the well-to-wheel
CO
2
emissions of EREVs and FCEVs and further improve the environmental compatibility
of these technologies.
However, the overall emission-free driving provided by FCEV technology makes it a very
promising future powertrain technology; it has the potential for broad application and
provides the greatest environmental compatibility. It also enables more functional designs
and offers refueling times comparable to conventional gasoline-fueled vehicles.
Meanwhile, EREV technology is an appropriate technology solution for today and will
maximize environmental benefits in the near term.
33. Internationales Wiener Motorensymposium 2012
Figure 22 – GM’s Advanced Propulsion Technology Strategy.
Bild 22 – GMs Strategie für zukünftige Antriebstrangtechnologien.
7. Summary
Market experiences with the GM EV1, Project Driveway fuel cell vehicles, and the
Chevrolet Volt and Opel Ampera extended-range electric vehicles have been very positive.
Customer feedback especially underscores the high appreciation consumers have for the
driving quality of fully electrified vehicles.
With the rapid progress on EV technology that has been made over the last decade, there
are many opportunities to electrify more vehicle segments. Although many of the physical
limitations of the various propulsion systems have to be addressed, BEV, FCEV, and
EREV systems provide the highest potential to reduce CO
2
emissions, especially if
renewable energy sources are used to produce the required electricity and/or hydrogen.
Concurrent with these advanced propulsion technologies, the electrification of more
conventional ICE powertrains will also increase as they incorporate mild hybrid or strong
hybrid systems across all vehicles classes. In addition, applications that are highly
sensitive to running costs, such as long-haul trucks, could also benefit significantly from
hybridization.
At the current state of technology, the BEV has range and vehicle mass limitations due to
the lower energy storage density of batteries, but it has potential in applications such as
city buses and small urban vehicles. EREV technology already allows all customers to
drive an average of 40 to 60 km per day on electricity without the need for a second
vehicle or restrictions to vehicle use. The EREV technology is therefore a significant
enabler for the widespread use of electric vehicles.
33. Internationales Wiener Motorensymposium 2012
EREVs and BEVs both provide opportunities for load leveling through smart charging. This
makes them a complementary technology to solar and wind power generation. In the
longer term, however, load leveling by hydrogen offers the greatest potential.
As noted, FCEV propulsion systems are applicable to all vehicle classes, but their
continuous power requirements have to be balanced against radiator size and the vehicle
package. Nevertheless, the FCEV is the only advanced propulsion option that provides
long-range zero-emission driving combined with a reasonably short refueling time.
Unfortunately, ubiquitous infrastructure remains a challenge. Establishing a fueling
network for hydrogen fuel cell vehicles requires a joint approach by all the major
stakeholders (e.g., auto, energy, and utility industries and government) and this must be
accomplished in parallel to vehicle rollout into the market. Large investment is required for
all future fuel options, including maintaining global oil supply.
Ultimately, the degree of electrification across the vehicle application map is a function of
energy prices, technology progress, infrastructure availability, the regulatory framework,
vehicle performance and fun-to-drive characteristics, and, finally, the overall customer
value proposition.
8. References
[1] http://www.kettering.edu
, Richard P. Scharchburg, Thompson Professor of Industrial History.
[2] Idaho National Laboratory: http://avt.inl.gov/pdf/EREV/GMJuly-Sept11.pdf.
[3] “The Car That Could”, by Michael Shnayerson, 1996, Random House, New York.
[4] Matthe, R; Turner, L; Mettlach, H; VOLTec Battery System for Electric Vehicle with extended
range, SAE World Conference 2011, 2011-01-1373.
[5] Anderman, M; Status of Li-Ion Battery Technology for Automotive Applications, Presentation
at SAE International Vehicle Battery Summit, Shanghai November 2011.
[6] Tom van Bellinghen, Umicore.
[7] Karlsruhe Institute of Technology, “MeRegioMobil” project, retrieved in December 2011,
http://meregiomobil.forschung.kit.edu/93.php
.
[8] U. Eberle, R. von Helmolt, Energy Environ. Sci., 2010, 3, 689–699.
[9] a) Statistical information provided by the German wind energy industry association, retrieved
in December 2012, http://www.wind-energie.de/infocenter/statistiken
.
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BDEW, „Arbeitsgemeinschaft Energiebilanzen“, presentation “Stromdaten Jahr 2011”,
retrieved in January 2011, http://www.ag-energiebilanzen.de/viewpage.php?idpage=65
.
[10] Pumped hydro store Goldisthal, technical specifications, retrieved in December 2011;
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[11] Michael Sterner, Michael Specht, Fraunhofer IWES and ZSW Center for Solar and Hydrogen
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http://www.abgnova.de/pdf/Sterner_IWES_Stadt_Frankfurt_ABGnova_2011.pdf
and “FVEE • AEE Themen 2009” , page 69 -78.
[12] U. Eberle, R. von Helmolt, “Auf dem Weg zur Kommerzialisierung”, Automobil Industrie,
December 2010. Also available in html format, retrieved in December 2011: http://www.e-
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[13] Argonne National Laboratory. (2011). GREET1_2011 (Greenhouse gases, Regulated
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.
[14] European Commision Joint Research Centre. (2011). Well-to-wheels Analysis of Future
Automotive Fuels and Powertrains in the European Context. Institute for Energy.
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