There's a new method for fueling cars. Instead of the usual dispenser nozzle, a plastic hose about the size of a sewage pipe is attached to the vehicle. An automatic clasp closes automatically around the tank opening.

The airtight hose system was developed by Germany's Linde conglomerate and has already been installed at several German gas stations. It's designed to allow the average person to fill his or her car with liquid hydrogen in just eight minutes. Berlin is one of the few places that already disposes of such a filling station.

Last week, German car-maker BMW used the facility to present car testers with the first small series vehicle in the world that drives on both gas and liquid hydrogen. The "Hydrogen 7," will be part of BMW's upscale "7" series of vehicles, and BMW is now carefully preparing to make the new car available to customers.

Starting in March, the car will be delivered to about 100 celebrities, but so far BMW is keeping mum about their names or what their leasing rates might be. The car's developers are hoping to gain insight into the practical reliability of a technology many consider the be all and end all of the car industry's ecologically clean and climate friendly future.

The Munich-based company is promising "sustainable mobility and sheer joy of driving," citing the car's 260 horsepower, 12-cylinder engine. The Hydrogen 7's standard combustion engine has been adapted to run on both liquid hydrogen and regular gasoline as well -- and tons of it. The company says the car will consume an average of 13.9 liters (3.7 gallons) per 100 kilometers (roughly 17 miles per gallon) using regular gasoline and a whopping 50 liters to drive the same distance when fuelled by hydrogen.

In other words, BMW has created an energy-guzzling engine that only seems to be environmentally friendly -- a farcical ecomobile whose only true merit is that of illustrating the cardinal dilemma of a possible hydrogen-based economy.

The problem is that hydrogen is in scarce supply and producing it requires vast amounts of energy. Climate-friendly production of liquid hydrogen on a large scale presupposes a virtually unlimited supply of ecologically produced electricity -- not something likely to materialize in the near future. That's why energy experts from the Wuppertal Institute for Climate, Environment and Energy believe forcing the transition to a hydrogen-based economy within the next three to four decades is "not an ecologically sound" idea.

Storing the volatile energy source also requires energy and money. The only method that promises a reasonable storage life is liquid storage at temperatures below -253 degrees Celsius (-423 degrees Fahrenheit). The process of cooling the storage facility down to such a low temperature alone uses up to one-third of the energy contained in one fuel tank.

Volatile fuel

BMW's thermo-tank, specially designed to hold liquid hydrogen as well as regular gasoline, has the same diameter as the drum of a washing machine. It has a volume of 170 liters (45 gallons) and takes up half the trunk. But it can only hold eight kilograms (17.6 lbs) of the extremely light hydrogen fuel -- barely enough for a 200 kilometer (124 mile) trip. What's more, some of the tank's contents have to be released as they heat up and evaporate -- even the best insulation system can't keep temperatures down forever. After nine days, half the tank load has gone bad.

BMW's competitors are somewhat puzzled by the company's decision to adapt combustion engines -- known for their high fuel consumption -- so that they will run on a fuel as sensitive and problematic as liquid hydrogen. "We think it's non-sense," says Frank Seyfried, research director for hydrogen-based propulsion at Volkswagen.

With the exception of BMW, every car company out there is betting on a different technology: fuel cells, which transform hydrogen into electricity via a chemical process. The electricity generated in the process then drives the vehicle. This method promises far greater efficiency, but the current technology yields only modest driving performance. Test cars with fuel cell engines can produce between 50 and 90 kilowatts, but they consume only about 14 liters of hydrogen per 100 kilometers (62 miles) -- a fuel value corresponding to that of four liters (one gallon) of gasoline.

BMW's chief developer Klaus Draeger still thinks there's good reason not to shelve the combustion engine. "It's the only engine that meets our requirements in terms of dynamics," he explains.

And so, in creating the Hydrogen 7, BMW is announcing a future of putatively clean, full-throttle driving. The new car caters to the pleasing fantasy of customers spoiled by high-horsepower engines: That they can conform to ecological standards without making any sacrifices, burning "clean" fuel to their heart's content. Advertizing images display the Hydrogen 7 against a backdrop of wind turbines and solar panels.