Honda new - Honda's hydrogen first - 2007

Honda has unveiled what it claims to be the world's first production hydrogen fuel cell car at the LA Auto Show.

The FCX Clarity is essentially the production version of the FCX prototype driven by Tom Ford back in June, and there's no denying it's a neat system.

A 171-litre hydrogen tank feeds the gas into the fuel cell stack, where hydrogen and atmospheric oxygen combine to produce electricity, with water as a by-product. That electricity drives a 134bhp motor, with any excess power stored in a lithium ion battery pack, which feeds supplementary electricity to the motor if needed. Regenerative braking also charges the battery.

Of course, it's seriously clean. Exactly how environmentally friendly the FCX is depends on the source of the hydrogen, but Honda reckons CO2 emissions from natural gas sources are less than half that of a conventional petrol car.

If the hydrogen is produced from water using sustainable electricity (work that one out: water and electricity produce hydrogen, which produces electricity and water...), CO2 emissions could theoretically be eliminated.

The big advances - and the reason that Honda has felt fit to bring the FCX to production - are in the size and efficiency of the fuel stack. Honda says the unit is 30 per cent lighter, 65 per cent smaller and 20 per cent more economical than its previous stack, giving more interior space and, thanks to the weight saving, improved economy and range.

Indeed, the FCX will cover 270 on a single tank, a decent range... so long as you can find somewhere to fill up with hydrogen at the other end.

Lack of infrastructure is the big problem facing hydrogen cars at the moment, and the reason that, unless you live in Southern California, you won't be driving an FCX for a good while. From next summer, Honda will lease a bunch of FCXs to drivers in SoCal for about £290 a month, but there's no word on when the car might roll out to the rest of the world.