DaimlerChrysler has just unveiled yet another fuel-cell prototype, to go with operational vehicles from themselves, Honda and others. The technology works. A fuel cell the size of an automotive air-conditioning unit takes hydrogen and oxygen and combines them to create electricity and water. Magic!
So are there really huge technical problems involved in making a fuel-cell vehicle, or FCV? Or is it just that vested interests - such as the oil industry - don't want you to have one?
To find out, I snuck into the Powertrain Congress in Ann Arbor, near Detroit. The media relations man warned me: "They won't be making it simple for journalists. There's a lot of algebra." I said I'd cope.
This was the first time the congress had devoted an entire session to fuel cells and hydrogen-based propulsion. As gas prices soar, even Americans are starting to look at alternatives. The speakers included chief engineers from GM, Nissan, DaimlerChrysler, Honda and BMW, which prefers the idea of burning hydrogen in a normal engine.
I also spoke to the chief executive of Ballard in Vancouver, Dennis Campbell. Ballard makes fuel cells, so Campbell naturally believes that FCVs are way better than sliced bread and more fun than conventional cars.
For a start, he says, because it won't have a great lump of engine, an FCV could have a 50/50 weight distribution for perfectly balanced handling. Performance won't be a problem, and all its torque is available from standing: "You can really squeal the tyres."
Everything would be controlled electrically, from steering and suspension to the wheels, which could be powered by individual motors. FCVs could program in desirable driving behaviour, and your family saloon could become a taut sports machine at the flick of a switch.
Dr Mohsen Shabana, chief engineer of GM's Sequel fuel-cell project, expanded on this in Ann Arbor. GM revealed the Sequel in January. The company calls its underpinnings a "skateboard chassis" - that's what it looks like - and Shabana lauded the design freedom it affords.
I have to admit to being disappointed with the Sequel car, which turned out to be a great Jeep-shaped 4x4. At Powertrain, Shabana explained that customers appear to like the familiar and don't go for inconvenience. To give the Sequel a 300-mile range, it needs three large tanks of hydrogen, so it is big enough to hide them under the floor without losing luggage space. So fuel cells and hydrogen storage systems need to become smaller, lighter and cheaper.
Doanh Tran, who works for DaimlerChrysler's Advanced Vehicle Engineering, was brave enough to put a date on commercial sales: 2012. The group boasts the biggest fuel-cell fleet of any manufacturer at more than 100 vehicles, and is running an intensive testing programme. This includes fuel-cell powered Mercedes buses in China and 60 F-Cell cars - actually A-class city cars - in the US and Europe. The fleet has clocked up one million miles, and parcel delivery service firm UPS has added a further 5,000 in an F-Cell and a Sprinter van.
Campbell says: "Governments need to commit to fleet purchases of hundreds of thousands of vehicles over the next five years. This would drive down the cost, develop maintenance and service industries, make the public familiar with the technology and drive energy companies to provide hydrogen fuel stations."
How do you make all that hydrogen without causing more pollution? In the immediate future, there is one surprisingly simple answer. No one expects a switch to hydrogen overnight, so FCVs and cars using oil-based fuels will need to coexist - and hydrogen is a byproduct of the oil refining process. A spokesperson from Shell said that the company generates 7,000 tons of spare hydrogen per day. Most is used for cleaning other products, but the rest can be offered as fuel.
Looking further ahead, Kiyoshi Handa, leader of Honda's hydrogen refuelling project, showed us photographs of the company's solar-powered station, which creates hydrogen from sunshine and water. Or, Honda has also devised a handy domestic unit that makes H2 from the natural gas already piped into your home, so you can fill up in your garage.
So it seems likely we'll be able to buy fuel-cell cars in less than 10 years, perhaps even five. All we need is for Leonardo DiCaprio to drive an FCV to the Oscars; then everyone will want one.