Is hydrogen the future of motoring?
The opening of the UK's first public refuelling station for hydrogen vehicles in Swindon is part of efforts to create a "hydrogen highway" along the M4 motorway.
It is also seen as an important step in a UK-wide scheme to make hydrogen vehicles a viable alternative to petrol-driven cars.
"A hydrogen car is much cleaner than a conventional car," says Professor Kevin Kendall, a hydrogen and fuel cell expert from Birmingham University.
"This will clean up our cities enormously," he says in an interview with BBC News. "No emissions whatsoever."
Hydrogen-powered cars rely on a fuel cell that takes oxygen from the air and combines it with hydrogen from a tank to create electricity.
The electricity is used to power electric motors, which turn the car's wheels.
As such, hydrogen-powered cars can be seen as electric vehicles that are not held back by the limited range of batteries.
"Your electric battery car does 60 miles [100km], this does 300 miles. It fills in five minutes rather than five hours," says Professor Kendall.
"This is the one for the future, there's no doubt in my mind."'Cheaper than electricity'
Creating a hydrogen refuelling infrastructure is essential for the future of hydrogen-powered motoring, which some carmakers see as the eventual future of so-called zero-emissions motoring.
End Quote Andy Palmer Nissan
I don't think [electric cars and fuel cell cars] necessarily compete with each other, any more than the diesel competes with the petrol engine”
"For long-distance driving, hydrogen fuel cells are very promising," according to Dieter Zetsche, chief executive of Daimler, the owner of Mercedes and Smart cars.
Rolling out the infrastructure will not be cheap, of course, but it might be a more cost-effective solution than the creation of a battery recharging infrastructure for conventional electric cars, says Dr Zetsche.
"For battery electric vehicles, you'll need infrastructure that is probably more costly than hydrogen," he insists.
"More charging stations mean more parking places are needed because it takes longer for them to refuel."
According to current estimates, creating a nationwide hydrogen refuelling infrastructure in Germany would cost between 1bn and 1.4bn euros ($1.4bn-$1.9bn; £870m-£1.2bn), though the eventual cost could be half that, Dr Zetsche says.
"So the cost is definitely not an obstacle to go into this area," he says.Recharging at home
Other carmakers are less concerned about costs relating to conventional electric motoring.
BMW, for instance, believes most people will charge their electric cars at home, so the need for an extensive infrastructure is not as great as many believe.
During 11 million kilometres of consumer testing with the company's electric Mini, it found that the average driver covered just 25 miles per day - well within the range of modern electric cars, says BMW's head of research and development, Klaus Draeger.
Consequently, the test drivers rarely recharged their cars away from their homes, and many of them only recharged their cars every two or three days, he says.
Nissan's global head of planning and marketing, Andy Palmer, agrees that there is only a limited need for an extensive infrastructure to recharge electric cars fast.
Instead, the existing grid and existing plugs will do the job for most of the people most of the time, he believes.
"If you think about the electric car, the infrastructure exists everywhere. The infrastructure is already there," he says.
"So you don't have the high investment costs you would have in putting down a hydrogen station."
He acknowledges there need to be some fast-chargers around the country to help those doing longer journeys top up their batteries, but this only takes 15 minutes with existing technology, he reasons.
"Now, think about it. When you go to a petrol station, next time you go just time how long you're waiting," he says.
"You're waiting in the queue to get to the pump, you put the pump in, you go from bottom to top and you spend an enormous amount of money, you go in the shop and you buy a cafe latte. I challenge you to do it in much less than 15 minutes."Not rivals
Today, there are really only two ways of executing zero emissions. One is the electric car, the other is the fuel cell, or the hydrogen car.
But is the choice between the two a realistic one? Neither Mr Palmer nor Dr Zetsche think so.
"It's not about discrediting battery electricity," says Dr Zetsche. "It's just about adding another solution for the future."
Mr Palmer says: "I don't think they necessarily compete with each other, any more than the diesel competes with the petrol engine. I think they both have their place.
"The good news is, a key part of both those solutions is the battery. Even the intermediary solution of petrol electric hybrids and plug-in hybrids rely on the battery."
Getting the cost of batteries down is therefore an essential part of all carmakers' efforts to achieve zero-emission motoring.
This is currently being done with large-scale investment into plug-in electric vehicles, and "clearly, we can use this technology to go across to fuel cell vehicles", he explains.
Professor Kendall is optimistic.
"People are making prototypes now," he says. "Every big manufacturer is making a hydrogen car now with a fuel cell.
"This is new technology, but by 2015 when it all kicks off, by 2020, there should be hundreds of thousands, if not millions of these cars around."
Clean energy required
The potential of electric vehicles and fuel cell vehicles to dramatically cut emissions from cars is tremendous, though the term "zero emissions motoring" needs to be treated with caution.
Both require the energy to be produced in the first place, whether to create electricity or to create hydrogen.
So to ensure the overall emissions that result from our transport needs are genuinely minimal, that power will either need to be created in nuclear power plants or it needs to come from renewable energy sources such as hydropower or wind farms.
So as long as fossil fuels such as coal and gas remain part of a nation's energy mix, the vision of completely emission-free motoring will remain a pipedream.