Vehicle Electrification - Quo Vadis? / Fahrzeugelektrifizierung - Quo Vadis?

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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

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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
Randbedingungen verschiedener Energieketten und
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
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
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.
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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

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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.

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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.

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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 CO2-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-

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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

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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
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”
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).
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).
CO2 and CAFE regulations: Improve efficiency and use less carbon-
based energy sources. Long-term petroleum price uncertainty drives
energy diversity.
2020s and
beyond
New technologies enable innovative, connected vehicle concepts.
1960s
1990s
2000s
2010s
Individual mobility in a highly populated world with limited resources.
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.

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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.

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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.

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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 material
Anode material
Electrolyte
Separator
Current collector
Cell housing

Both cell design and the electrolyte impact specific power (W/kg) and cost.

Cathode and Anode
Material Effect
Cell Voltage
Specific energy (Wh/kg)
Energy density (Wh/liter)
Cycle and calendar life
Abuse tolerance
Cost

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Cathode
Material
Acronym
LCO
Cathode
Material full
Application Pro Con
Lithium Cobalt
Oxide
Notebook,
Phone
Power Cost of cobalt
(high content),
abuse tolerance
Nickel and cobalt
cost
LNMC Lithium Nickel
Manganese
Cobalt
Lithium
Manganes Oxide
EREV, EV Life
LMO EREV, EV Low material
cost,
Safety
Power,
cycle life,
calender life
Life at temp
>40°C
NCA Lithium Nickel
Cobalt
Aluminium
HEV,
Notebook,
Phone,
Cost of nickel
and cobalt (high
content), limited
abuse tolerance
Lower energy
density
LFP Lithium Iron
Phosphate,
"Olivine"
Power tools,
EV
Low material
cost,
Safety
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.

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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.

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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.

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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.