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FEATURE - A squeaky clean future for the car?

17.09.2002  |  125× přečteno      vytisknout článek

SINDELFINGEN, Germany - Unlike the sleek and snarling Mercedes coupes screaming around DaimlerChrysler\'s test track, the lowly Chrysler \"Town and Country\" mini-van consumes neither petrol nor diesel. It runs on soap.

The plain white mini-van does not have the Mercedes\' looks, its power steering is broken and the acceleration is leisurely - but as it arcs round the banked curve of the circuit at Sindelfingen near the south German city of Stuttgart, this everyday vehicle may be the car of the future. In tubes and tanks under the chassis, something very like soapy water mixed with hydrogen called sodium borohydride and similar to borax found in laundry detergent, is being tested as one of the latest ideas to power a car with a fuel cell. Fuel cells use hydrogen and oxygen to make electricity and water. Add an electric motor and you can build a car which emits no pollutants. That makes them an attractive alternative to fossil fuels which, in vehicles, produce a tenth of the carbon dioxide contributing to global warming and a range of other pollutants which give rise to acid rain, smog and respiratory diseases. Some have heralded hydrogen as the energy of the future, but sceptics say it will always be just that - a future fuel which for a host of reasons never makes it out of test cars. SODIUM BOROHYDRIDE THE SOLUTION One problem is that hydrogen is difficult to store - as a gas it is very bulky and in liquid form it needs to be kept at -253 degrees Celsius (-423.40 degrees Fahrenheit). The DaimlerChrysler \"Natrium\" vehicle on the test track at the firm\'s Sindelfingen factory gets round this by storing the hydrogen as sodium borohydride, a non-toxic solution that can be pumped in and out of the vehicle safely and cleanly. The van can travel 500 km (300 miles) on one tank, has a top speed of 130 kmh (80 mph) and feels like any other car to drive. Unlike hydrogen, the sodium borohydride \'fuel\' is non-flammable and relatively compact. When brought into contact with a ruthenium cobalt catalyst, one of the platinum group metals, it gives off hydrogen which is fed to the fuel cell. The spent solution, sodium borate, is pumped back to the fuel tank and separated from the fresh fuel by a bladder. At the fuel station, it is pumped out, replaced with fresh sodium borohydride, and can then be recycled. The process was developed by Millennium Cell , a tiny U.S. company set up to market the technology. Ingenious though it is, there are still some teething problems, said Bernard Robertson, a senior vice president in charge of engineering technologies at DaimlerChrysler. At present, a \"stabiliser\" chemical has to be added to the sodium borohydride, which makes it very alkaline and causes it to lose its non-toxic status. There are also problems recycling the spent sodium borate cleanly. \"The objective was to prove the principle, and then refine it,\" said Robertson. RIVAL TECHNOLOGIES But even when such technical glitches are ironed out, there are bigger questions surrounding hydrogen power. Who will pay to build the new fuel stations, without which no consumer will want to buy a hydrogen car? And which, if any, of the systems will be adopted? Will everyone use sodium borohydride, or liquid hydrogen, or compressed hydrogen gas, or hydrogen stored in tiny \"nanotubes\" of carbon, or methanol or petrol which can be \"reformed\" on board the car? Or, like luxury German carmaker BMW , will industry, consumers and politicians eschew fuel cells entirely and plump for a traditional internal combustion engine powered by liquid hydrogen? In the United States, matters are further complicated by the cheap cost of petrol. Robertson said the Natrium vehicle\'s running costs would probably be equivalent to $2.50 a gallon - roughly double today\'s U.S. filling station prices. \"If the alternative fuel has to compare to a $20 barrel of oil, everything is going to have an uphill struggle,\" said Robertson. The logic behind fuel cell and hydrogen research for the carmakers, who have built their fortunes on the internal combustion engine, is that governments, especially in Europe, are cracking down on emissions. And in the United States, President George W. Bush has become an unlikely advocate for fuel cells - he has been shown the Natrium test car - as part of a policy of reducing U.S. reliance on oil imports. So far, though, the carmakers have taken a conservative path. DaimlerChrysler, the world\'s number five car maker with yearly revenues of around 150 billion euros ($146.3 billion) (dollars), says it will have spent $1 billion on researching the technology in the 14 years to 2004. WELL-TO-WHEEL If the aim is to reduce the overall impact on the environment, a further issue arises in measuring how \"green\" such cars are. Although the Natrium car and pure hydrogen fuel cell vehicles emit no pollutants, the process of creating the hydrogen might do so if, for example, the hydrogen is made by electrolysis with electric power from a coal-fired power plant. Looking at the whole process has become known as \"well-to-wheel\" analysis as opposed to \"tank-to-wheel\" in industry jargon. Hans-Joachim Schoepf, head of Mercedes-Benz passenger car development, said the fuel cell offers the best well-to-wheel environmental performance. But it is a long-term aim - he expects conventional internal combustion engines to be with us for another 30 years, albeit refined to use ever less fuel and supplied with cleaner burning petrol or diesel. The preliminary findings of a European study commissioned by U.S. carmaker General Motors concludes that fuel cell vehicles could greatly reduce greenhouse gas emissions, if the hydrogen is generated from renewable sources such as wind power. That is a long way off though, and a more realistic alternative is for the hydrogen to be extracted from natural gas. This still creates greenhouse gases, but, the GM study said, is an improvement on diesel or petrol. The report also said internal combustion engines fuelled by liquid hydrogen from natural gas actually produce higher well-to-wheel greenhouse gas emissions than either petrol or diesel engines. That throws a spanner in BMW\'s proposed hydrogen car. \"Our opinion about fuel cells is they are not ready to be used in the drive line,\" said BMW board member Burkhard Goeschel. He said BMW only planned to use small fuel cells in its cars as power units for the vehicle\'s electronics. Back at the test track, though, the Natrium car\'s engineers say the fuel cell is here to stay. \"You see those cars,\" said engineer Euthemios Stamos, pointing at the Mercedes roaring past as he monitors the van\'s fuel cell performance on a laptop computer. \"They are the result of 120 years of people working on gasoline engines. \"It\'s going to take a lot of work to get the fuel cell to the same point, but this stuff works.\" Story by Michael Steen REUTERS NEWS SERVICE

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