BMW's Hydrogen 7

I had the chance to try the Hydrogen 7 yesterday at the SMMT test day, and a quick spin around the high-speed bowl at Millbrook showed that while the current 7 has been around for a few years now, it's still pretty good to drive, and also that its impressive performance and refinement do not seem to suffer when this specially-converted version is running on hydrogen.

In fact the Hydrogen 7 is capable of using either hydrogen or unleaded and can even be switched between the two fuels on the move at the press of a button, a change that is scarcely felt at all by driver or passengers.

I haven't looked into hydrogen in as much detail as I have bio-fuels, but I understand that BMW's approach of using liquid hydrogen to power a combustion engine is comparatively unusual; my guess is that this is thought by the company to be the best way of developing cars that can run on alternative fuels but still retain the sporty qualities drivers value in a BMW.

One drawback is that the separate hydrogen tank used by this model eats into the 7's boot space (see photos below), although this is probably no worse than the boots of Lexus' big hybrids, which suffer a similar problem. This does however, remind us of a big advantage enjoyed by cars that can run on bioethanol-based E85, where both unleaded and the alternative fuel can be mixed in any proportions in the same fuel tank and use the same pipework.



At the moment, only about 100 Hydrogen 7s are being built and there is just one UK fuelling point (at Wembley in North London). It's difficult to see big numbers of liquid hydrogen cars being sold, at least until the infrastructure is better developed, but at least BMW is pushing things along. In the meantime, though, the measures incorporated into standard models under the manufacturer's Efficient Dynamics programme, such as cutting, and then automatically restarting, cars' engines when stopped, and exploiting regenerative braking, are likely to have more of an impact.

Greenery. There are other ways - perhaps

When it comes to green PR, Toyota seems to be making most of the running at the moment. Hollywood stars have been flocking to the Prius for a good few years now, and Toyota's hybrid also enjoys an exemption from the London congestion charge - evidence of some effective lobbying work, I guess. Honda gets quite a bit of kudos for going down the hybrid route too, while Ford, and especially Saab, have also won a certain amount of recognition for offering cars that can run on E85, which is 85% renewable bioethanol.

But a couple of other manufacturers are now starting to pipe up, and are politely pointing out that you can get some pretty good results in terms of fuel consumption and CO2 emissions without resorting to drastic solutions like stuffing a car full of batteries and electric motors, or switching to alternative fuels.

Citroen, for example, recently published a pamphlet listing some of its achievements in this area. This mentions its new C4 BioTech which can run on E85, and a prototype diesel hybrid C4, but the emphasis is very much on what it's already been able to do with smaller changes to mainstream cars - small diesel engines that have tailpipe emissions that are almost as low as those of the Prius, particulate filters, Sensodrive automated manual gearboxes and stop-start mechanisms that shut down the engine when a car is stationary and automatically restart when you go to set off.

BMW is another manufacturer that is introducing a lot of these smaller changes in its mainstream cars, as I discovered when I spent yesterday trying some of the company's revamped models in Wiltshire. The main visible changes are modest (to my eye barely noticeable) facelifts for the 1-series and the 5-series, and the introduction of a new pretty three door version of the 1. Under the skin, though, there is a bit more going on, a series of improvements that are being introduced piecemeal to different models under the general heading 'Efficient Dynamics'. This comprises stuff like better diesels, energy-saving electric power steering, regenerative braking and a stop-start system similar to Citroen's. The idea is to save fuel without cutting down on the sort of driving enjoyment that BMWs are famous for, and in this the company seems to have succeeded. I was able to try the revised 535d and 118d; the latter had the stop-start system, which works almost imperceptibly; the engine is cut out if you put the car into neutral with the brakes on, say when you stop for a traffic light. The engine restarts immediately as soon as you depress the clutch and put the car into gear. I was impressed to discover that a by-product of the new start system is the car's ability to restart automatically if you stall it as I did on one occasion.



It wasn't all incremental changes, though; for the longer term, BMW is betting on hydrogen in liquid form. I had a chance to see, but not to drive, a 7 series converted to run on the fuel; this had part of its bodywork cut away to show off the big hydrogen tank that sits between the boot and the back seat. There's a chance the Independent may get to try one of these priceless cars - there is a limited production run of 100 for the time being, with only a few making it to the UK - later this year, so I'll be eager to see whether I can get my hands on it.