TESLA ROADSTER: THE NEW STANDARD OF ELECTRIC AUTOMOBILES

Cara Hutter
Tyler Starmack
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
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
University of Pittsburgh April 2, 2013
Swanson School of Engineering
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