Transport - May 9
by Staff
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... The recommendations are:
(8 May 2008)
As the cost of running gas-guzzling tractors soars, even-toed ungulates are making a comeback, raising hopes that a fall in the population of the desert state’s signature animal can be reversed. “It’s excellent for the camel population if the price of oil continues to go up because demand for camels will also go up,” says Ilse Köhler-Rollefson of the League for Pastoral Peoples and Endogenous Livestock Development. “Two years ago, a camel cost little more than a goat, which is nothing. The price has since trebled.”
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. ... DISCUSSION This analysis shows that light personal vehicles perform far better than heavy ones. Energy used to produce vehicles and transportation infrastructure was not considered here, and such an analysis would make light vehicles appear even more attractive. For all payload weight classes, the payload to vehicle mass ratio of the best performers is between three and four. Since most people tend to travel individually when possible, and energy resources are becoming increasingly scarce with respect to demand, it would appear that personal vehicles of the future will be very light by today’s standards. A challenge in the development of urban transportation infrastructure will be to allow for safe use of these personal vehicles amidst heavier cargo and mass transit vehicles. ... |
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