Vidi kôd stranice Economist hownottosavepetrol

<font size="1">29th January 2000</font>
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face="Arial, Helvetica, sans-serif" size=3><B>SCIENCE AND TECHNOLOGY
 
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<FONT face="Arial, Helvetica, sans-serif" size=3><B>Fuel-efficient cars</B></FONT><BR>&nbsp;<BR>
      <DIV><FONT face="Arial, Helvetica, sans-serif" size=6>Hybrid vigour?</FONT> </DIV>
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<font size="1">D E T R O I T</font>
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'''A subsidised programme designed to deliver fuel-efficient cars to Americans has done so. But the results are not cheap and may be obsolete within a decade'''
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DESPITE some modest increases in petrol prices last year, fuel economy is not much of an issue for most American car owners. Their government, however, begs to differ—to the tune of $240m a year. That is the amount of taxpayers’ money which it has spent for the past six years on the Partnership for a New Generation of Vehicles (PNGV), a collaboration with the country’s car builders to develop vehicles so efficient that even the greenest of environmentalists will have difficulty complaining about the amount of fossil fuel they guzzle. 
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The first of these so-called supercars, the Precept (built by General Motors) and the Prodigy (Ford), have just been unveiled at the Detroit motor show. They achieve the equivalent of 80 miles per American gallon of petrol (35km/litre), a third of the consumption of current American saloon cars and better, even, than existing fuel-efficient cars such as Toyota’s Prius and Honda’s Insight. But even more important, they address the main criticism of those existing cars—that they are too small (the Insight is a two-seater) and thus too un-American.
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The Precept and the Prodigy (and a yet-to-be-revealed prototype from DaimlerChrysler) could not be accused of a lack of American values. They are about the same size as the Chevrolet Lumina and the Ford Taurus. They should, however, deliver the magic 80mpg by a mixture of attention to technological detail and the introduction of a “hybrid power pack”, which uses a combination of electric and diesel motors to deliver energy more efficiently, and recycles as much of it as possible. 
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<font size="3">Thirsting for economy</font> 
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In even the best of today’s cars, more than 70% of the energy in the fuel tank is wasted by the time the rubber meets the road. The biggest consumers of energy are friction in the engine, friction between the tyres and the tarmac, poor aerodynamics and “parasitic losses” in components such as the oil and water pumps. On top of that, there is the obvious point that big vehicles tend to be heavy, and thus require more energy to accelerate and decelerate them. 
That is a long list. As a result, the PNGV’s participants have had to rethink virtually every aspect of car design, from the shape of the body to the chemistry of the tyres—as well, of course, as the engine. The Precept’s bodyshell, for example, has the most wind-slippery design ever achieved. Its engineers have even replaced the wing mirrors with lipstick-sized cameras that send images to two dashboard-mounted displays. On top of that, its chassis and body make extensive use of lightweight materials such as aluminium, magnesium, titanium and plastic composites. The result is that the car weighs 1,190kg (2,618lb)—barely two-thirds the mass of the Lumina. Moreover, high-efficiency pumps reduce parasitic losses, and the Precept boasts tyres which are less flexible than ordinary ones and so dissipate less energy. 
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But the real key to the vehicle’s miserly fuel consumption is found under its bonnet. The Precept marries a 1.3-litre direct-injection diesel with two electric motors, one on each axle, powered by a 35kW lithium polymer battery. The result is known as a “heavy” hybrid, meaning that the electric motors are powerful enough to run it without assistance from the diesel engine. In normal urban driving they will do so about two-thirds of the time—with snazzy electronics deciding when to cut the diesel in and out. They also act like superchargers when the vehicle accelerates. On top of that, when the driver hits the brake pedal the coils and magnets in the electric engines act as braking generators—slowing the car down by converting its energy of motion into electricity, which is then squirted into the battery. 
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The Prodigy, by contrast, is a “light” hybrid. It has the same sorts of energy-saving tricks as the Precept, but its single electric motor, which is powered by a nickel-metal hydride battery, does not have enough oomph to move the car by itself. Instead, its role is to provide assistance to the vehicle’s 1.2-litre direct-injection diesel engine when it is accelerating. Such assistance is, however, enough to allow the Prodigy to rely on a diesel barely half the size of that in the otherwise similarly sized Taurus. 
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This all sounds marvellous. But it will not be much good if people are unwilling to buy the new cars. The Prius is heavily subsidised by Toyota to keep it affordable, and Ford’s and GM’s executives admit that even their supercars will be several thousand dollars more expensive than conventional models. 
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That might not matter in countries where fuel is expensive. But in America, it isn’t. Tripling the fuel-efficiency of the average American saloon car would, according to Ford, save about 371 gallons a year. That sounds a lot, but it is actually worth less than $500. So it is not surprising that a recent study by Dohring, a research firm, showed that although Americans favour cleaner, more fuel-efficient vehicles in principle, they are unwilling to pay much more for them than they would for a traditional gas-guzzler. 
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The hybrid engine also looks like being a blind alley. When the PNGV began in 1993, hybrids seemed smart. Not only would fuel be saved, but emissions could be kept down in town, where people might breathe them, while an internal-combustion engine would provide serious power for intercity driving. But technology has moved on since then. The future almost certainly belongs to the fuel cell, a way of generating electricity which is powerful enough for intercity driving, and which is exhaust-free everywhere. GM also unveiled a fuel-cell-powered version of the Precept at the show. And fuel cells have not required a quarter of a billion dollars a year of taxpayers’ money.
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            size=4><B>LINKS</B></FONT> <BR> <BR>
Click [http://www.ta.doc.gov/pngv/cover/pngvcover.htm here] to go to the Partnership for a New Generation of Vehicles’ website. Ford has issued a [http://www.ford.com/default.asp?pageid=70&storyid=625 press release] about Prodigy. For more background information about the partnership, read the Library of Congress’s [http://www.cnie.org/nle/eng-9.html report], published in 1996.  <BR><BR>
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