Power Requirements

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The world’s transportation systems are expanding every day, and with expansion comes the rapid depletion of natural resources, ever increasing environmental degradation, more traffic congestion, and a higher frequency of accidents.

The United States, with four million miles of highways, railroads, and waterways, 130 million passenger cars, 88 million buses and trucks, 230,000 aircrafts, 1.4 million miles of oil and gas pipelines, 40,000 ships, numerous railroad cars and boats, and 20,000 airports, has the largest transportation system in the world (1). Every day about 13 million barrels of petroleum, more than 2/3 of total US petroleum consumption and 27% of its entire energy use, are required to operate this huge system (Table 1) (2). Because most of these fuels are imported, the US must seek ways to reduce its reliance on foreign oil either by increasing fuel efficiency and switching to alternative fuels or by reducing total miles traveled by investing in mass transit systems and carpooling, bike riding, and walking.

Table 1. Transportation Energy Use by Mode, 2005
Modes Trillion BTU Percent of total
Light Trucksa
Heavy Trucks
Total 27,065 100
a Including SUVs

Reference: Davis, S. C., Diegel, S. W., Table
2.6. “Transportation Energy Data Book,”
ORNL-6978, Edition 26, 2006.

Although most transportation issues are global in nature, because of the sheer size of the US transportation system, its role as a major technological powerhouse, and due to the fact that it is the biggest contributor to environmental pollution, this chapter focuses mainly on US data.

We discussed the concept of energy and power in some detail in mechanical energy. Briefly, energy is what is needed to carry out a given task without concern for the time it takes to accomplish it. Power is the rate at which the energy is used and therefore determines the speed at which the task is performed. Without sufficient energy, we cannot go very far without having to refuel. If everything else remains the same, a larger fuel tank (more energy) makes it possible to drive longer distances, whereas a larger engine (more power) allows a vehicle to reach its destination faster, carry a greater load, or climb steeper roads. A major concern in any design of land, air, or marine vehicle is the power required for operation under various conditions.


(1) Transportation Statistics, Annual Report 2003, US Department of Transportation, Bureau of Transportation Statistics, Washington, DC 20590, 2003.

(2) Davis, S. C., and Diegel, S. W., Transportation Energy Data Book, Oak Ridge National Laboratory, Edition 24, 2004.

(3) Toossi Reza, "Energy and the Environment:Sources, technologies, and impacts", Verve Publishers, 2005

Further Reading

Tillman, D., Fuels of Opportunity: Characteristics and Uses In Combustion Systems, Academic Press, 2004.

Sorensen, K., Hydrogen and Fuel Cells: Emerging Technologies and Applications, Academic Press, 2005.

Dhameia, S., Electric Vehicle Battery Systems, Academic Press, 2001.

Hussain, I., Electric and Hybrid Vehicles: Design Fundamentals, CRC Press, LLC. 2003.

Jefferson, C.M., and Barnard, R. H., Hybrid Vehicle Propulsion, WIT Press, 2002.

Spelberg, D. The Hydrogen Energy Transition: Moving Toward the Post Petroleum Age in Transportation, Academic Press, 2004.

Fuel, Direct Science Elsevier Publishing Company, Fuel focuses on primary research work in the science and technology of fuel and energy fuel science.

Transportation Research Part C: Emerging Technologies, Direct Science Elsevier Publishing Company; this journal focuses on scholarly research on development, application, and implications in the fields of transportation, control systems, and telecommunications, among others.

Fuel Cells Bulletin, Direct Science Elsevier Publishing Company, Fuel Cells Bulletin is the leading source of technical and business news for the fuel cells sector.

International Journal of Hydrogen Energy, Direct Science Elsevier Publishing Company, Quarterly journal covering various aspects of hydrogen energy, including production, storage, transmission, and utilization, as well as economical and environmental aspects.

External Links

US Department of Transportation (http://www.dot.gov).

US Department of Energy (http://www.doe.gov).

US Environmental Protection Agency (http://www.epa.gov).

National Energy Renewable Laboratory Hybrid Electric &Fuel Cell Vehicles (http://www.nrel.gov/vehiclesandfuels/hev).

FreedomCar (http://www.eere.energy.gov/vehiclesandfuels).