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Session A9
Paper 3096
TESLA ROADSTER: THE NEW STANDARD OF ELECTRIC AUTOMOBILES
Cara Hutter (cdh32@pitt.edu, Bursic 2:00), Tyler Starmack (tas143@pitt.edu, Bursic 2:00)
Abstract-In recent years, reducing energy consumption and
emissions has been a priority for those with economic and
environmental concerns. Electric automobiles provide an
improvement upon existing automobiles by completely
eliminating the need for oil and gasoline. Some automobile
companies, such as Chevrolet and Nissan, have developed
their own models of electric cars; however, Tesla Motors
was created primarily for the design, development, and
production of electric cars. One such car, the Tesla
Roadster, uses rechargeable Lithium-ion batteries, which
provide a very high energy density at a relatively low cost.
This paper will explain how electricity is a suitable,
more efficient, and economical alternative to gasoline by
comparing the Tesla Roadster to a similar gasoline-powered
car. It will also discuss, in detail, the mechanics behind the
three main systems of the Tesla Roadster. In addition, the
paper will describe the performance of the Roadster, as it
pertains to the efficiency and emissions produced by the car.
Within the discussions of efficiency, emissions, and
performance of the Roadster, the sustainability of the vehicle
will also be analyzed.
Hesitation to purchase an electric car is primarily based
on the fact that most have insufficient power and a limited
range. However, Tesla Motors shows that the correct use of
technology allows the Roadster to contradict popular belief.
Therefore, the Tesla Roadster will likely become the
standard for electric cars in the near future.
Key Words-Efficiency, electric automobiles, internal
combustion engine, Lithium-ion battery, Tesla Motors, Tesla
Roadster
INTRODUCTION: THE NEED FOR A NEW
STANDARD
Often, when one thinks of an electrically powered
vehicle, something akin to a golf cart is pictured-not usually
powerful or reliable. This may change, however, in the years
to come. Since its establishment in 2003, the all-electric
automotive company, Tesla Motors, has been testing,
developing, and designing cars that will run on only
electricity, not gasoline. Their goal is to change the
automotive industry by developing sustainable technology
for cars that will eliminate harmful emissions and the need
for gasoline (and thus, foreign oil) [1].
Their most groundbreaking design, the Tesla Roadster,
includes both of these elements as well as having an
attractive design and comfortable interior. The technology
involved, while quite complex, is actually simpler and far
superior in efficiency to a standard car with an internal
combustion engine. Because of its superiority to cars on the
road presently, it is likely that the technology in the Roadster
will become the new standard in all automobiles in the
coming years.
A BRIEF HISTORY OF TELSA MOTORS
Tesla Motors was founded in 2003 in Silicon Valley,
California for the purpose of developing and manufacturing
cars that run only on electricity. The roots of this company
can be traced back to Stanford’s Solar Car project, in which
a team of students led by J.B. Straubel created and raced a
car that used only solar power. Although their car finished
fifteenth in the race, the student engineers realized that it
was possible to run the car without the use of solar energy if
they used a larger Lithium-ion battery. This idea inspired
J.B. Straubel, with the help of PayPal founder Elon Musk, to
establish Tesla Motors [1].
Although the company had high ambitions, it faced
extreme challenges that it had to overcome in order to stay in
business. As Georgios Sarakakis, Noah Lassar, and Christian
Frederickson say in their paper concerning the development
of the Tesla Roadster, “It [Tesla Motors] was a small startup company in an industry of big, established brands
requiring large capital investment” [2]. Because of this,
Tesla Motors had to work especially hard to keep themselves
in business by developing quality products that would be
desirable to consumers. This in itself was a challenge
because the technology for electric automobiles was largely
unproven and therefore not trusted by average consumers.
In order to overcome this challenge, Tesla Motors
engaged in extensive data collection of the Roadster and
continues to work to improve designs even after they appear
on the market. They also own all of their stores so that
accurate records of service events are kept. In this way,
Tesla Motors is able to collect more data on aspects of the
vehicle that are malfunctioning in order to continue to
improve its design as well as gaining the trust of the
customer by providing quality service.
In addition to the challenge of catering to the wary
consumer, Tesla Motors also had to face the challenge of
finding quality materials for which to construct the Roadster.
Since electric vehicles eliminate the use of gasoline, the
entire mechanical layout of the car is different. There is no
need for an engine in such a car, only electrical components.
Because these components are entirely different than
anything that is normally used, Tesla Motors had to build a
new supply chain in order to acquire the materials needed.
This was especially difficult because the Roadster was being
developed in the late 2000s during the recession that hit the
United States. Engineers from Tesla said, “Often, suppliers
were either unwilling to work with a small electric vehicle
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start-up, or their capabilities were not up to the quality,
reliability, and performance goals of the Roadster” [2]. Tesla
Motors has since been able to create an effective supply
chain that allows them to manufacture their vehicles.
The fact that Tesla Motors has worked (and continues to
work) so hard to overcome the challenges of being a small
start-up company developing new technology shows that
they are extremely committed to their goal of creating
efficient, reliable, and affordable electric cars as well as
possibly providing other car companies with this technology.
An article from Stanford magazine about the beginnings and
future plans of Tesla Motors says, “They’re out to inspire
change, not dominate the market,” and J.B. Straubel himself
says, “The long term goal is to transform the whole
transportation industry, not just make a better sports car” [1].
The Roadster is indeed an amazing sports car, but it is only
the beginning for Tesla Motors in their quest to develop
affordable electric vehicles that the average consumer is able
to purchase.
Lithium-ion batteries are presently quite popular in
technology (used in cell phones, laptops, etc.). They are very
recyclable- 96 percent of their materials can be recovered,
and they are often reused before they are recycled because
they can still carry a substantial charge, thus making them a
great sustainable energy source. They are also quite
lightweight and have a high energy density. This means that
a battery of this type can store a large amount of energy
relative to its size, which makes it perfect for use in an
electric vehicle. If an electric car were to not use Lithiumion batteries, it would instead use nickel metal hydride
batteries, which are much heavier and have a low energy
density. Such a car would require more than a thousand
kilograms of them [4].
FIGURE 2
ELECTRIC INNOVATIONS: THE
TECHNOLOGY BEHIND THE TESLA
ROADSTER
Before comparisons between the Tesla Roadster and
gasoline-powered cars are made, it is important to
understand the technology behind the Roadster. Because it is
an all-electric car, the components that cause it to run are
completely different than a car with a standard internal
combustion engine (ICE). The following sections will
describe the three main systems that make the Roadster
work: the Electronic Storage System (ESS), the Power
Electronics Module (PEM), and the electric motor. These
systems can be seen in the diagram below (Figure 1).
FIGURE 1
DIAMGRAM OF SYSTEMS [3]
The Electronic Storage System (Battery Pack)
Because the Roadster does not use gasoline, it must get
power from another source. In this car, power comes entirely
from a battery pack called the Electronic Storage System
(ESS), which is made up of Lithium-ion cells (Figure 2).
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ELECTRONIC STORAGE SYSTEM [3]
Since Lithium-ion batteries have a high energy density, it
is very important that the battery pack be safeguarded
against overheating. In the Roadster, such precautions are
taken to ensure overheating does not occur among other
issues that arise with the use of electricity (i.e. short
circuits). This is done mainly through the layout of the
battery pack and the addition of devices within the pack.
Each of the Lithium-ion cells is 18 millimeters in
diameter and 65 millimeters in length (slightly larger than a
AA battery) and 69 of them are wired together in parallel to
make ‘bricks’. Nine of these ‘bricks’ are wired together in
series to make a sheet (Figure 3), and 11 sheets are inserted
into the case (Figure 4) [5]. The advantage of having many
sheets of batteries is that it greatly increases the surface to
volume ratio. Engineers at Tesla say, “Surface area is
essential to cooling batteries since the surface is where heat
is removed; more is better” [4]. Because the cells are wired
into sheets, there is space between these sheets for a
temperature control device. In addition, there is a device
called a Current Interrupt Device (CID), which responds in
the event that a cell has excessive internal pressure which is
a result of high temperature. If this event occurs, the CID
will break, causing no current to flow into the cell, thus
isolating it from the others. If these cells were not isolated
when such an event occurred, it could set off a chain
reaction that would affect the other cells and cause more
severe damages.
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FIGURE 3
another system to control how much energy is being drawn
from it, which will be discussed in the next section.
The Power Electronics Module
SHEET OF 621 BATTERIES [3]
FIGURE 4
ELEVEN SHEETS OF BATTERIES ARE PLACED IN
THE CASE [3]
In addition to controlling the temperature of the battery
pack, there are also devices in place to prevent electrical
malfunctions such as short circuits. Each cell has two fuses,
one on the cathode (positive end) and one on the anode
(negative end). These fuses are designed to blow (break) if
the electrical current passing through them is above a certain
amount. A sudden increase in current is usually the result of
a short circuit. When either one of the fuses break, the cell is
completely separated electrically from the rest of the cells,
eliminating the chance of it harming the others. Each of the
sheets also has a fuse to prevent short circuits across the
whole sheet [4].
Also within the ESS are numerous microprocessors and
sensors that, under normal circumstances communicate with
the vehicle to monitor the state of the ESS (such as
temperature and amount of charge). Under more adverse
circumstances however, these systems have the ability to
signal to the high voltage contractors to disconnect the
battery pack (which has a high voltage that can be
dangerous) from the car [4]. This prevents the high voltage
from harming the driver.
It is very fitting that the ESS would have all of these
safety features since it is one of the most important systems
of the Roadster. The Lithium-ion batteries are the reason that
it has enough power to travel more than 200 miles on a
single charge as well as accelerate from 0 to 60 miles per
hour (mph) in less than four seconds [4]. This system cannot
exist on its own in the Roadster, however. There must be
As stated above, the ESS must have some other system
to control how much and what kind of energy must be drawn
from it. This system is called the Power Electronics Module
(PEM) and is a vital part of the Roadster’s technology. Tesla
Motors says that it, “functions as a bridge for energy
between the charge port, battery, and the motor” [6]. This
means that all of the energy that the Roadster uses must
travel through this system at some point.
The PEM in its most basic use controls current. The ESS
stores power in what is called direct current (DC), but the
current that comes from charging sources (i.e. power outlet)
and the current that the motor uses is alternating current
(AC). Current that is referred to as direct only flows in one
direction, whereas alternating current reverses direction
periodically. One of the PEM’s main functions then, is to
convert current from AC to DC or vice versa [6].
In order for the PEM to function effectively, there are
three main systems that work together: the power stages, the
controller, and the line filter. The power stages, also known
as the Megapoles, are arrays of switches that control whether
the battery is connected to the charge port or the motor.
Within the Megapoles there are six switches grouped in pairs
called half-bridges, each of which form a phase in the motor
(this will be discussed in greater detail in the next section).
Each of the six switches is composed of 14 Insulated Gate
Bipolar Transistors (IGBT) (Figure 5). These IGBTs control
the amount and type of current that is passed through the
PEM. The IGBTs create alternating current by turning off
and on rapidly [6].
FIGURE 5
IGBTs [6]
The system that manages these switches is the controller,
which has the ability to turn the switches on and off up to
32,000 times per second. The controller contains two
processors called the digital signal processor (DSP) and the
secondary safety processor. The DSP is mainly responsible
for interpreting requests from the Vehicle Management
System, controlling torque, and changing behaviors of the
system. The secondary safety processor, on the other hand,
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functions as a current monitor. If the current going to the
motor is inconsistent with the acceleration pedal, it will stop
the system [6]. This prevents the Roadster from accelerating
more than the driver intends.
The last system in the PEM is the line filter. The line
filter is a series of inductors (devices that store energy in
magnetic fields) called chokes that are placed between the
charge port and the IGBTs. Their purpose is to filter out
electrical noise which is a result of the IGBTs are turning off
and on at a rapid rate while the Roadster is charging. This
noise, if allowed to conduct back through the power lines,
would cause interference in other electronic devices such as
radios and cell phones [6].
The PEM is indeed a complex system that is incredibly
important to the Roadster. It, in combination with the ESS,
provides the necessary power to run the electric motor,
which will be discussed, in detail, in the next section.
The Electric Motor
The ESS and PEM are vital to the functioning of the
Roadster-they would mean nothing if the electric motor did
not exist. In order for the car to drive, the motor is essential
because it is connected to the back axel and therefore the
wheels. The type of motor that the Roadster uses is called a
three-phase AC induction motor, and is one of the most
common types of electric motors (Figure 6).
FIGURE 6
ELECTRIC MOTOR [7]
The motor consists of two main parts: the rotor and the
stator (Figure 7). The rotor consists of a steel shaft with
copper bars running through it. As the rotor turns, the wheels
do as well, moving the car. The stator is stationary and
encases the rotor, but does not touch it. 900 amperes (amps)
of current are delivered to the stator through copper wires
(used for their low resistance, and therefore can endure more
current) that are wound through a stack of steel plates. There
are three sets of these wires, each corresponding to the three
phases of the motor [7].
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FIGURE 7
CROSS SECTION OF ELECTRIC MOTOR. ROTOR:
INNER BLUE CIRCLE, STATOR: OUTER RING [8]
As the alternating current from the PEM flows through
the copper wires in the stator, a magnetic field is produced
that, like the current, alternates between a North and South
Pole. The three phases of the motor occur because of the
three sets of alternating currents in the three sets of wires.
The magnetic fields resulting from each set of wires are
slightly out of time with each other. This creates a ripple of
magnetic field travelling around the stator. Tesla Motors
describes this by way of analogy, “The magnetic field
appears to move in a circular path around the stator- similar
to the way spectators in a sports stadium create the illusion
of a ‘wave’ by alternating between standing or sitting in
concert with other fans” [7].
The magnetic field from the stator then induces a current
in the copper bars within the rotor, which then creates an
opposite magnetic field around the rotor, due to Lenz’s Law.
This law states, “An induced current has a direction such
that the magnetic field due to the current opposes the change
in magnetic flux that induces the current” [9]. This means
that the rotor will have a magnetic field that is opposite of
the stator, and because the magnetic field of the stator is
constantly moving around in a circle, the rotor will spin to
follow it. This, in turn, will provide the torque that is
necessary to spin the wheels. The rotor is also positioned in
such a way that its magnetic field is always “behind” the
stator’s. This ensures that the rotor keeps spinning. This also
means that the farther behind the rotor is from the stator, the
more torque is being produced (when accelerating) [7].
Torque, then, is always being produced as long as the
rotor is spinning. This means that there is no need for this
type of automobile to have a transmission with gears since it
produces effective torque at a wide range of rpms (rotations
per minute). This simplifies the running process of the
Roadster to an extreme degree since there are little to no
timing issues possible (unlike a car with an ICE). There is
also no reverse “gear” in the Roadster. All that needs to be
done in order to put the car in reverse is to switch two of the
phases of the motor so the magnetic field runs in the
opposite direction. This completely eliminates the need for a
transmission, and thus increases the Roadster’s efficiency
and contributes to its sustainability, which will be discussed
in the next section [7].
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SUSTAINABILITY OF THE ROADSTER
The sustainability of the Tesla Roadster comes solely
from the types of technology included in its make-up. The
Lithium-ion batteries, for example, contribute heavily to its
environmental impact as well as its energy sustainability.
They prove to be quite recyclable since 96 percent of each
cell can be recovered. This is done simply by bringing them
to a plant where they are shredded and sorted through to
recover the metal components. In most cases, however, they
are reused before they are recycled. A Lithium-ion battery
typically still has about 80 percent of its charge left after it
can no longer be used by a car, so it is then used for other
purposes, such as in solar panels and windmills, before it is
recycled [10]. It is in this way that the batteries contribute to
the overall sustainability aspect of the Roadster. They reduce
the amount of waste by being reused and recycled, rather
than being thrown away. Also, the fact that they are more
powerful than other batteries for their size also means that
less have to be made.
But Lithium-ion batteries are not the only things that
make the Roadster more sustainable. The electric motor
contributes a very large degree to sustainability through its
efficiency. The efficiency of the motor is mostly due to the
fact that it does not need to convert energy or motion very
drastically. For example, in an ICE car, in order to achieve
rotational motion in the wheels, it must be converted from
the linear motion of the pistons. In an internal combustion
engine, the pistons move up and down in sequence in order
to turn the driveshaft. The driveshaft then connects to the
differential to which an axel (front or rear) is attached to.
This then causes the wheels to turn. This is very unlike the
electric motor, which is connected directly to an axel and
turns the wheels. There is no need for so many conversions
in motion. In fact, the electric motor used in the Tesla
Roadster achieves 88 percent efficiency- much unlike an
ICE which has about 30 percent efficiency [7].
It is largely because of the motor and batteries, then, that
the Roadster can claim to be part of the sustainability
movement. These two pieces of technology cause the car to
use almost all of the energy supplied to it, rather than much
of it being wasted, as well as have little environmental
impact.
Sustainability is based on the principle that everything
needed for survival depends on the environment [11].
Therefore, the technology used in everyday life should be
made to reduce harmful emissions that are released into the
atmosphere. Automobiles certainly fit into the category of
this form of technology. Currently, the conventional,
gasoline-powered vehicle emits tremendous amounts of
harmful carbon dioxide into the atmosphere, which prevents
it from being classified as sustainable. The Tesla Roadster
provides an improvement upon current automobiles by
increasing efficiency and reducing emissions, thus making it
a more sustainable form of transportation. This increased
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sustainability provides the foundation of the value behind
the Tesla Roadster.
TESLA ROADSTER: A COMPARISON TO
GASOLINE-POWERED AUTOMOBILES
To show the value behind an electric automobile,
specifically the Tesla Roadster, it is necessary to compare
the Roadster to similar gasoline-powered vehicles. This
section will compare three main differences between the two
types of vehicles: efficiency, emissions, and performance.
The sustainability of the Roadster will also be analyzed
during each comparison.
Efficiency
In order to provide an accurate representation of the
efficiency of a vehicle, the overall, well-to-wheel energy
efficiency must be computed. Well-to-wheel efficiency is
the best overall representation of the efficiency of a vehicle
because it combines both the efficiency of the car itself and
fuel production from the well to the wheel of the car. The
computation of efficiency of a car is done in four steps. The
first step is to consider the energy content of the source fuel
as it comes from the ground (i.e. coal, crude oil, or natural
gas). Next, the energy content of the fuel is tracked as it is
converted to its final product, either gasoline or electricity.
Then, the energy needed to transport the fuel to the car is
subtracted from the total amount. Finally, the fuel efficiency
of the car is used to complete well-to-wheel efficiency [12].
As a reference, energy content of fuels will be presented in
terms of mega-joules per kilogram (MJ/kg), and overall
efficiency is expressed in terms of kilometers driven per
mega-joule (km/MJ) of fuel consumed [12]. A higher wellto-wheel efficiency describes the more efficient vehicle. A
comparison between the Tesla Roadster and the similarly
built, gasoline-powered Honda Civic VX will show the
difference in total efficiency. The 1993 Honda Civic VX
will be analyzed first.
Gasoline’s energy content is roughly 47 MJ/kg, and the
production and transportation of gasoline is 81.7% efficient
on average. This means that 18.3% of gasoline’s energy
content is lost during production and transportation. The VX
has an Environmental Protection Agency (EPA)-rated 51
miles-per-gallon (mpg) of gasoline combined city and
highway driving. Therefore, its efficiency is 0.52 km/MJ. A
typical car gets half the mpg of the VX, making it the most
efficient gasoline-powered vehicle made to date [12].
A combined cycle, natural gas-fired electric generator is
considered to be the most efficient way to generate
electricity [12]. The best of these generators is 60% efficient,
meaning that 40% of the natural gas’s energy content is lost
in generation. However, the recovery, processing, and
transportation have a combined average efficiency of 87.5%,
giving a total production efficiency of 52.5%. In the Tesla
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Roadster, the Lithium-ion batteries are about 86% efficient,
and the car’s efficiency is 2.53 km/MJ. Taking into account
the production efficiency, the well-to-wheel efficiency is
1.14 km/MJ [12].
Figure 8 presents the well-to-wheel efficiency of six
different vehicles. Each vehicle is run by a different form of
technology. The Honda CNG is a natural gas engine, the
Honda FCX is run by a hydrogen fuel cell, the VW Jetta
Diesel uses a diesel engine, and the Toyota Prius is a hybrid,
which combines both gasoline and electricity. It is clear that
the Tesla Roadster has a much greater well-to-wheel
efficiency than any other type of automobile. In fact, it is
more than double its nearest competitor, the Toyota Prius.
Since gasoline, oil, and natural gas are all nonrenewable
resources, meaning they will become depleted in the future,
limiting their use is essential to ensure sustainability. The
Roadster, and electric cars in general, only use a fraction of
these resources compared to gasoline-powered vehicles.
Additionally, the resources that are used in making
electricity are used more efficiently by the Roadster than any
other vehicle with fewer emitted emissions, which will be
analyzed in the next section.
FIGURE 8
dioxide emissions can be calculated. Therefore, the overall
emission of the VX is 141.7 grams/kilometer (g/km), and the
emission of the Roadster is 46.1 g/km [12].
In this case, a smaller well-to-wheel carbon dioxide
emission is more desirable. Figure 9 shows compares the
overall emissions of each of the same vehicles described
before. It is again quite clear that the Tesla Roadster
outmatches its competitors. With a total emission that is 3.07
times less than the Honda Civic VX and 2.83 times less than
the hybrid Toyota Prius, the Roadster shows that electric
automobiles can help to significantly reduce the amount of
carbon dioxide that is released into the atmosphere.
During the process of burning fuel, many different types
of emissions are produced, including carbon dioxide. Most
of these greenhouse gases are released into the atmosphere,
which can cause significant damage, specifically the ozone
layer. Lowering automobile emissions is one way to ensure
the protection of the environment and atmosphere. The
limited carbon dioxide emissions of the Roadster provide
another example of the sustainability of the vehicle.
Most vehicles that are considered high performance, for
example, the Porsche Turbo or Ferrari Maranello, have
incredibly high carbon dioxide emissions. Even though the
Tesla Roadster is a high performance car, which will be
shown in the next section, the carbon dioxide emission is
significantly less than any other high performance vehicle.
FIGURE 9
WELL-TO-WHEEL EFFICIENCY [12]
Emissions
Using the energy efficiency of a vehicle and the carbon
content of the source fuel, it is possible to calculate and
compare the well-to-wheel emissions of any form of vehicle.
However, the main focus of the emissions comparison will
again be between the Tesla Roadster and the Honda Civic
VX.. During the process of combustion, when the fuel is
burned, all of the carbon in a vehicle’s fuel source becomes
carbon dioxide, which can be harmful to the atmosphere
[12].
Crude oil, the fuel source of the Honda Civic VX, has a
carbon content of 19.9 grams per mega-joule (g/MJ), while
natural gas has a carbon content of only 14.4 g/MJ. Every
gram of carbon is converted to 3.67 grams of carbon dioxide
because of the two oxygen molecules added to each carbon
molecule. So, the content of carbon dioxide in crude oil is 73
g/MJ, and natural gas has a carbon dioxide content of 52.8
g/MJ. By dividing carbon dioxide content by each vehicle’s
respective overall efficiency, the well-to-wheel carbon
WELL-TO-WHEEL CARBON DIOXIDE EMISSIONS
[12]
Overall Performance
The main drawback to owning a car like the Tesla
Roadster is the purchase price of the vehicle. With a base
price of about $109,000 [2], the Roadster is several times
more expensive than a conventional gasoline-powered
automobile. This high price is primarily due to that fact that
the number of electric automobiles being sold is greatly less
than their gasoline counterpart. Until the volume of sales of
electric cars is comparable to gasoline-powered cars, it will
be necessary to compare other aspects of the two vehicles.
Efficiency and emissions point greatly in favor of electric
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automobiles, but what really sets the Roadster above and
beyond its competition is performance.
Performance, which is measured by a combination of
torque, or horsepower, and efficiency, gives the Tesla
Roadster an edge over gasoline-powered vehicles. An
internal combustion engine produces a very small amount of
torque at a low number of revolutions-per-minute (rpm) and
can only supply reasonable horsepower in a small range of
rpm [12]. However, as shown in Figure 10, the Roadster
delivers high torque from very low rpm to around 6,000
rpm. It can also continue to produce torque well beyond the
point of any combustion engine, although the amount of
torque begins to slowly decline after 6,000 rpm [7].
Although the base price of the Roadster may appear to
point away from the vehicle’s sustainability, the high price is
only temporary. Once the new technology of the Roadster
becomes more commonly used and the volume of
production of electric automobile increases, the price will
continually drop [12]. The combined efficiency, emitted
emissions, performance, and innovation of Tesla Motors will
allow the Roadster to be a sustainable vehicle in the future.
FIGURE 11
FIGURE 10
ACCELERATION COMPARISON [12]
TESLA MOTORS: SETTING THE
STANDARD
TORQUE PRODUCTION OF AN ELECTRIC MOTOR
AND GASOLINE ENGINE [7]
Efficiency plays a large role in the production of
horsepower. With a gasoline engine, performance comes
with large consequences. Due to the complexity of the
internal combustion engine, a large amount of energy is
wasted. At best, only about 30% of the energy stored in
gasoline can be converted into torque. In order to overcome
the internal losses of the engine, the vehicle must idle at
around 1,000 rpm [7]. Additionally, the acceleration of an
automobile is based on the horsepower of the engine. If
rapid acceleration is desired, a high-horsepower engine is
required, which will lead to very poor gas mileage [12].
However, an electric motor is able to convert electricity into
mechanical power, while acting as a generator, turning
mechanical power back into electricity with an overall
efficiency of 88% [7]. Incredible efficiency and torque
production allows the Tesla Roadster to accelerate as well
as, if not better than, the best sports cars of today [Figure
11]. As shown in Figures 9-11, the Roadster is able to
perform at a very high level, while being six times more
efficient and producing one-tenth the emissions of other high
performance vehicles, including the Porsche Turbo, Ferrari
Maranello, and the Chevrolet Corvette [11].
When the Tesla Roadster took to the streets in 2008,
skepticism and major challenges plagued Tesla Motors. The
unproven technology from a small start-up company added
to the hesitation to purchase the Roadster. Public perception
of electric cars only increased the skepticism to purchase an
all-electric performance sports car. Tesla Motors sought not
only to fight these challenges, but to change the public
perception of electric vehicles. In order to succeed in the
market, it was necessary for Tesla Motors to use a rapid
production and improvement of their products [2].
Tesla Motors demonstrated its commitment to
improvement through the Roadster. In its first three years on
the market, Tesla Motors upgraded the design of the
Roadster four times, which is a record for a new car
company [2]. Each new design brought improvements to
nearly every major aspect of the car. Range, performance,
and reliability have increased [Figure 12], and the interior
and exterior styling also improved with each design change
[2]. The improvements made to the Roadster are a direct
result of the innovative processes used by Tesla Motors.
University of Pittsburgh
Swanson School of Engineering
April 2, 2013
7
Cara Hutter
Tyler Starmack
FIGURE 12
VEHICLE FAILURES PER 100 THOUSAND MILES
(2008-2011) [2]
Innovation is a key requirement in any company,
especially those which have just entered the market, and
Tesla has proven to be a leader in the advancement of
electric automobiles. Tesla Motors uses a mobile service
team, called the Tesla Rangers, to perform most service calls
at the customer’s house [2]. The Rangers offer a very unique
and convenient method of servicing a car. Instead of leaving
a vehicle at a shop and waiting until the appointment is over,
customers can simply call the Rangers and never have to
leave their home. Tesla also demonstrates that an electric
car, such as the Roadster, is much different than its gasolinepowered counterpart by showing that vehicle improvements
do not always require the need of a mechanic. Most
improvements are simply updates of the firmware (software)
and not changes to the hardware [2]. Firmware updates can
even be done remotely with permission and assistance from
the customer [2].
The innovation of Tesla Motors has helped the
company to succeed despite the challenges it faced. The
Tesla Roadster also has shown that electric cars are not just a
futuristic dream. Lithium-ion batteries, an Electronic Storage
System, the Power Electronics Module, and the electric
motor have already been developed enough to allow the
Roadster to travel up to 245 miles per charge. Efficiency,
emissions, and performance of the Tesla Roadster are overall
much better than a conventional vehicle. Each of these
aspects contributes towards making the Roadster a more
sustainable vehicle. In fact, in an interview with MIT
Professor Donald Sadoway, he said, “The only reason that
(electric) car isn't everywhere: it couldn't go more than 70
miles on a charge. But you make it 270, game over.
Anybody who drives it will never go back to internal
combustion” [12]. With a 245 mile range, it seems clear that
Tesla Motors achieved its goal of changing the public
perception, and they may have even set a new standard in
the electric automobile industry.
REFERENCES
[1] A. Marsh. (2008). “The Electric Company”. Stanford
Magazine.
(Online
Article).
http://alumni.stanford.edu/get/page/magazine/article/?article
_id=31675.
[2] G. Sarakakis, N. Lassar, C. Fredrickson. (2011).
“Reliability insights from 15 million electric miles”. Tesla
Motors. (Online Article).
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6
175469.
[3] (2011) “Tesla Motors Club”. Tesla Motors. (Online
Article).
http://www.teslamotorsclub.com/showthread.php/3810Roadster-battery-(ESS)
[4] G. Berdichevsky, K. Kelty, JB Straubel, E. Toomre.
(2007). “The Tesla Roadster Battery System”. Tesla Motors.
(Online Article).
http://webarchive.teslamotors.com/display_data/TeslaRoadst
erBatterySystem.pdf.
[5] (2013) “Battery”. Tesla Motors. (Online Article).
http://www.teslamotors.com/roadster/technology/battery
[6] (2013) “Power Control”. Tesla Motors. (Online Article).
http://www.teslamotors.com/roadster/technology/powerelectronics-module
[7] (2013) “Motor”. Tesla Motors. (Online Article).
http://www.teslamotors.com/roadster/technology/motor
[8] (2013) “Basic Polyphase Devices” (picture). Industrial
Electronics Information for Manufacturing Applications.
http://www.industrial-electronics.com/polyphasedevices/Basic-Polyphase-devices.html
[9] D. Halliday, R. Resnick, J. Walker. (2012).
Fundamentals of Physics: Extended, Ninth Edition. John
Wiley & Sons, Inc. (Print book). pp. 794.
[10] K. Hall-Geisler (2011). “Can Electric Car Batteries Be
Recycled?”. How Stuff Works. (Online Article).
http://www.howstuffworks.com/can-electric-car-batteriesbe-recycled.htm
[11] (2013). “Sustainability”. Environmental Protection
Agency.
(Online
Article).
http://www.epa.gov/sustainability/basicinfo.htm.
[12] M. Eberhard, M. Tarpenning. (2006). “The 21 st Century
Electric Car”. Tesla Motors. (Online Article).
http://www.stanford.edu/group/greendorm/participate/cee12
4/TeslaReading.pdf
ADDITIONAL SOURCES
E. Grabianowski. (2011). “How the Tesla Roadster Works”.
How
Stuff
Works.
(Online
article).
http://auto.howstuffworks.com/tesla-roadster.htm.
ACKNOLEDGEMENTS
We would like to thank the writing staff for their assistance
in class and helpful resources. Their explanations provided a
clear and understandable overview of the task of this paper.
We would also like to thank Ross Hutter for his assistance in
selecting an interesting and relevant topic.
University of Pittsburgh
Swanson School of Engineering
April 2, 2013
8