IEEE Electrification Magazine - December 2013 - 7

he average internal combustion engine (ice)-propelled automobile is roughly 10-20% efficient on average at converting the energy in gasoline into forward motion. the remainder of the energy is dissipated into heat
or ejected and not fully burned. this means that 80-90% of the fuel is wasted.
if you consider an analogy where a person filling the gas tank pumped 1-2 gal
into the tank, then pumped 8-9 gal onto the ground, you begin to understand just how much
fuel your automobile can waste. this may startle those who might think of their vehicle as
clean burning and energy efficient; but, as we will see, the numbers actually get much worse.
if the vehicle's mission is to transport a payload from point to point, then the mission efficiency depends on the ratio of the weight of the payload to the weight of the vehicle. Frequently, the
driver is the only payload in the vehicle. the typical
driver's weight is roughly 5% of the combined
weight, yielding a mission efficiency of less than 1%
(10-20% combined thermodynamic and system efficiency multiplied by 5% payload efficiency = 0.5-1%
mission efficiency). so based on our earlier analogy,
now consider the example that 1-2 gal are in the
tank and 8-9 gal on the ground but realize that 95%
of the energy from the 1-2 gal that made it into the
tank will be required to move the weight of the vehicle, while only 5% of the energy will actually move
the person to their destination. often, when people
hear these numbers for the first time, they are
astonished that automobiles could be so inefficient.
Yet, engineers who understand the laws of thermodynamics will readily verify them. the next time you fill your gas tank, look at the total cost of
the fuel and realize that less than 1% of the fuel will move you from place to place-the rest is
essentially wasted in terms of your mobility.
so the next time you hop in your car and buckle up to drive a short distance, for example, to
the grocery store to get a few items, you may want to think about the fact that you just strapped
on 4,000 lb or so of steel to move your far-lighter body a mile or two to get a small bag of groceries.
the energy you consume is probably around 200-500 Wh/mi instead of about 10-15 Wh/mi on a
bicycle. driving a typical conventional car consumes about 20-50 times more energy than riding
a bicycle (which has additional health benefits).

Superlightweight
designs improve
energy consumption,
battery size or range,
cost of the vehicle,
and acceleration
performance.

energy Wasted in Transportation on a Global Scale
now, let us consider how our single-car example measures up on a global scale. there are
roughly 1 billion vehicles globally, consuming about 70% of oil production, or about 60 million
barrels of oil per day, for transportation. personal transportation, i.e., cars, sport-utility vehicles,
minivans, and light trucks, consume about 36 million barrels of petroleum per day at less than
1% mission efficiency on average. they emit nearly 17 billion t of carbon and roughly 114 trillion
btus of heat every day. the vehicle base is projected to double in 15-20 years. at current efficiency levels, those 2 billion vehicles would consume roughly 120 million barrels of petroleum
per day, a rate that raises concerns about oil production capabilities to supply fuel. the refining
process yields about 33 gal of transportation fuel in the form of gasoline, diesel, and jet a fuels
for aircraft (along with other products). so roughly 4 billion gal of transportation fuel are projected to be burned, daily, in 15-20 years. these numbers have significant air quality, health,
and economic consequences.
at roughly 20 lb of carbon dioxide (co2) per gallon of fuel consumed, the daily quantity of
co2 generated by transportation would be about 80 billion lb/day or 29 trillion lb/year of co2. in
such quantities, co2, plus the other emissions generated in the process of burning fuel each
day, raises serious concerns about global climate change and the breathability of air, especially
in high-density urban and suburban areas where more than 50% of people globally will live.
transportation is the second-highest contributor to carbon emissions, behind coal-fired
power plants. the above data suggest that increasing transportation efficiency can
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Table of Contents for the Digital Edition of IEEE Electrification Magazine - December 2013