Ticking Time Bomb

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A modern car's engine, idling, driveline, and accessories dissipate seven-eighths of its fuel energy. Only one-eighth reaches the wheels. Of that, half heats the tires and road or heats the air that the car pushes aside. Only the last 6 percent accelerates the car (then heats the brakes when you stop). And since about 95 percent of the mass being accelerated is the car, not the driver, less than 1 percent of the fuel energy ultimately moves the driver—unimpressive, considering it is the fruit of 120 years of engineering effort.

Happily, three-fourths of a car's propulsive energy need is caused by its weight, and every unit of energy saved at the wheels saves another seven units we don't need to waste on the way to the wheels. Thus, making cars that are radically lighter weight has huge fuel-saving leverage.

Lighter weight formerly meant costly metals such as aluminum and magnesium. Now, ultralight steels can double a car's efficiency without extra cost or decreased safety. With clever design, even conventional steels can yield surprising results. A German startup firm's 2+2-seat 450- to 470-kilogram diesel roadster (http://www.loremo.com) combines 160- to 220-kilometer-per-hour (100- to 137-mile-per-hour) top speeds with a fuel economy from 1.5 to 2.7 liters per 100 kilometers (87 to 157 miles per U.S. gallon), and will sell in 2009 for 11,000 euros to 15,000 euros.

Advanced polymer composites are even stronger and lighter. They can halve a car's weight and fuel use, yet increase safety, because carbon-fiber composites can absorb up to 12 times as much crash energy per kilogram as steel. Such materials can make cars big (comfortable and protective) but not heavy (hostile and inefficient), saving both oil and lives. A new manufacturing process (see sidebar) can even make a carbon-fiber car cost the same to produce as its steel version. That's because its costlier materials are offset by simpler automaking and a smaller propulsion system.

 

For example, an uncompromised mid-size sport named Hyper carutility vehicle (SUV) designed in 2000 equipped with the most popular efficiency-doubling hybrid-electric drive system, could carry five adults in comfort and up to two cubic meters of cargo, haul a half-ton up a 44 percent grade, accelerate from 0 to 100 kilometers per hour in 7.2 seconds, be safer than a steel SUV even if it hits one, yet use less than a third the normal amount of gasoline, getting about 3.56 liters per hundred kilometers, or 67 miles per U.S. gallon.

If produced at a rate of 50,000 cars per year, its retail price would be $2,510 (in year 2000 U.S. dollars) higher than today's equivalent steel SUV, but only because it is hybrid-electric, not because it is ultralight. Saved gasoline would repay this investment in two years at U.S. fuel prices or one year at European Union or Japanese fuel prices. Manufacturing such cars would use far less space and two-fifths less capital than today's leanest plant, thanks to up to 80-fold less tooling and to elimination of the body shop and paint shop—the two hardest and costliest steps in automobile manufacturing.

 
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