From the outside, it looks like just another vehicle
Richard Hollingham reports from California on how technology that took man to the Moon could soon take shoppers regularly to the mall.
It looks like an ordinary SUV (Sports Utility Vehicle), the sort of chunky 4X4 you'll find jamming American roads.
It's only when you take a drive that you realise that this is something very different.
I'm no motoring correspondent but, as we pull out of the parking lot, it's difficult not to be impressed by this car's smooth acceleration.
What's even more disconcerting is that the vehicle is almost totally silent - the only noise comes from the wind buffeting the windows and the squeal of the tyres as we bomb down the freeway.
"The car drives with electricity but - unlike a battery-electric car that you need to plug in to charge - the fuel cell vehicle makes electricity on-board from the hydrogen stored in a tank," explained Catherine Dunwoody, executive director of the California Fuel Cell Partnership.
"The fuel cell is a fuel conversion device that converts hydrogen to electricity," she told the BBC World Service's One Planet programme.
The only byproduct is water - the ultimate 'zero-emission' vehicle.
The partnership, based in the Californian state capital Sacramento, was set-up 10 years ago to promote fuel cell vehicles and involves carmakers, energy companies and government agencies.
And although "fuel conversion device" sounds terribly futuristic, the basic technology of the fuel cell has been around for more than 150 years.
Today's space shuttles have three fuel-cell power plants on-board
Like a battery, a fuel cell uses a chemical process to generate electricity. Inside the fuel cell, a catalyst strips hydrogen into positively charged hydrogen ions and electrons. The positive ions pass across a special membrane and react with oxygen (from the air) to form water. The electrons have to take the long way round and flow through a circuit to generate electricity.
But with a world powered by coal and oil, no-one knew what to use these things for, until Nasa needed a way to power its spacecraft.
The agency turned to British engineer Francis Bacon.
During the Apollo 8 mission of 1968, Bacon told a BBC reporter how excited he was to see "a real genuine use for a fuel cell".
When it came to powering Apollo (and the previous Gemini missions), fuel cells were perfect. Less bulky than batteries and more efficient than 1960s solar panels, they even produced a useful by-product: water, which the astronauts could drink.
So, great if you want to go to the Moon but it's still been a struggle to apply the technology back on Earth.
Various US government initiatives have come and gone, fuel cell cars have remained as prototypes. There are hydrogen fuel cells around but they've proved to be a niche market. That could, finally, be about to change.
Just how clean?
A quick scout through a list of California's hi-tech start-up companies and you'll find many of them devoted to the technology.
"There are a lot of people working on fuel cells in California," Fritz Prinz, the chair of mechanical engineering at Stanford University, said.
"They are trying to create new ideas, making fuel cells more cost effective, more efficient, for a variety of different applications from personal power to mobile applications such as cars."
The first hydrogen fuel cell cars are due to go on sale in the next five years and with governments keen to wean their nations off oil, they would seem to be a viable alternative.
California has an intensive programme of research on fuel cell technology
But a number of issues remain. Hydrogen fuel cell cars need hydrogen and, even in California, there are only around 25 filling stations in the whole of the state. The other problem is even more fundamental: where does the hydrogen come from?
"Most hydrogen today is made from natural gas," admitted Ms Dunwoody.
So although the cars are technically zero emission, the process of making the hydrogen produces carbon dioxide.
Nevertheless, she said, it was still greener than burning it.
"When you make hydrogen from natural gas and use it in a fuel cell vehicle, you immediately cut your carbon emissions by 50%. But there's a lot of work going on in California on creating renewable hydrogen," and that includes using hydrogen produced from wastewater biogas.
The ultimate goal is to produce an efficient way of extracting hydrogen from water. Imagine that? Cars powered by water.
What's certain is that without the effort that went into getting a spacecraft to the Moon, the development of efficient, useful hydrogen fuel cells would be nowhere near as advanced as it is today.
Said Dunwoody: "This is our future, this technology is tremendously efficient and clean and, most importantly, it's going to give customers the performance they expect from their vehicle."
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