"The Energetic Performance of Vehicles" was published on May 7th in
the peer-reviewed "Open Energy and Fuels Journal." This article may
be downloaded from:
http://www.bentham.org/open/toefj/openaccess2.htm
ARTICLE SUMMARY:
Energy can take various forms, one of which is kinetic, or the energy
of motion. Another form is thermal energy, which is the lowest, most
unorganized form of energy. The thermal energy in a gallon of
gasoline or a candy bar may expressed in Joules or calories. Kinetic
energy of a person on a bicycle or in a car can also be expressed in
the same units.
Fuel economy ratings such as miles per gallon of gasoline provide one
measure of vehicle performance. In comparing transportation options,
average speed is also important. One can travel about the same number
of miles per calorie of thermal energy in a full jumbo jet, or on
one's own two feet. Of course, very few of us would consider walking
from New York to California because it would take so much more time
than flying. Some may consider bicycling, but probably more for the
experience of the trip than arrival in California or reduction in
carbon footprint.
An analytical consideration of the interplay between speed and motor
power was described in an age of petro-abundance (1950) in a paper
entitled, "What Price Speed," published by Gabrielli and von Karman.
Use of maximum instead of average values, motor output instead of fuel
input power, and gross vehicle weight instead of payload mass resulted
in a parameter decoupled from fuel economy and practical transport
benefit.
The most universal way to characterize the energetic performance of a
vehicle is to compare the kinetic energy of the payload to the rate of
thermal energy use. This parameter is expressed in seconds and easily
calculated from fuel economy values, payload mass and average speed.
"The Energetic Performance of Vehicles" includes a logarithmic graph
comparing energetic performance of many vehicles, such as bicycles,
cars, ships, airplanes and rockets powered by burning food in a human
engines, or coal, uranium, and natural gas in electrical powerplants,
gasoline in internal combustion engines, jet fuel in turbines, or
solid propellant in rocket motors. Time averaged speed and fuel
consumption are shown to form the basis for intermodal transport
comparisons of benefits, emissions, and resource use.
--
Jeff Radtke
jr@cloudchambers.com
www.cloudchambers.com