By Michael Shields In Nabern, Germany
 
Just imagine filling up your car at the windmill down the road.

That is what Andreas Truck-enbrodt dreams of but DaimlerChrysler's director of fuel cell and alternative powertrain vehicles knows there are still hurdles to clear before zero-emission cars become kings of the road.

"The consensus in the industry now is that we will see the first commercial fuel cell vehicles on the street from around 2010," he said.

Mr Truckenbrodt - a self-described car guy who helped develop the SLR super sports car that Daimler builds with McLaren before he switched to fuel cells - presented a vision of new-age cars and trucks blending into the scene, not exploding to life.

"We expect that we will see a variety of internal combustion engines - petrol and diesel, hybrids, natural gas, alternative energy and fuel cells for a relatively long time as each has advantages for specific applications." he said.

But there are still technical obstacles to overcome and the issue of setting up infrastructure to tap the unlimited supply of hydrogen and wean the world from its dependence on crude oil.

Technical issues include extending fuel cells' reliability and durability; ensuring that they start at sub-freezing temperatures; reducing costs, and storing enough hydrogen in a small enough space to be workable.

"I firmly believe that none of these points is a show-stopper," Mr Truckenbrodt said, but the technology still needs time, money and practical experience to attain its potential.

There is practically no political opposition to embracing fuel cells, which use the chemical reaction between hydrogen and air to generate electricity and emit only water vapour. That paves the way for a potentially huge market that carmakers and technology firms are chasing at top speed.

DaimlerChrysler, which rolled out its first fuel cell delivery van a decade ago, has already invested around £685 million in the campaign even though Mr Truckenbrodt said it was impossible to forecast when the business would produce a profit.

Prices for the vehicles have to fall dramatically before they can compete for customers. That means manufacturers have to boost volumes, simplify the technology and cut material costs.

"The volume issue is certainly a tough one, but we see here and at others carmakers that the number of units is gradually rising from generation to generation," Mr Truckenbrodt said, which also helps bring down prices for materials.

But even a leader like Daimler will have only some 100 fuel cell test cars on the street by the year's end, plus dozens of buses and some delivery vans which are being tried out around the world.

Reliability should eventually be good because, unlike standard engines, there are no moving parts in the stack of fuel cells that powers vehicles.

But the membrane that separates the hydrogen from oxygen dries out over time and tends to rip, ruining its efficiency. Daimler is working on this with membrane manufacturers.

In the race to bring out commercially viable fuel cell vehicles, Daimler is competing against other carmakers, hybrid technology that combines electric motors with standard motors, and the still-dominant internal combustion engine itself.

Mr Truckenbrodt noted it would be easy to hook up filling stations to the underground hydrogen pipelines that already serve chemical companies in some areas of Europe.