FEATURE - A squeaky clean future for the car?
Date: 16-Sep-02
Country: GERMANY
Author: Michael Steen
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.
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