Monday, April 04, 2005

Green with ENV

The ENV Bike and its adaptable Core fuel cell is, perhaps, the most exciting thing to happen in personal transport since the Model T. Fuel cells look like being the only way in which the internal combustion hegemony may be challenged. The Core cell, however, is flawed in its reliance on pure hydrogen as an energy carrier.

Hydrogen is not a fuel. No it isn't - listen.

A fuel is something which may be gathered, like wood, coal, crude oil, camel dung or uranium and may have energy extracted from it, usually by a thermal process. Admittedly, if free hydrogen could be harvested in useful quantities it would be a fuel, by this definition, but free hydrogen doesn't stick around long in nature.

'But what about the hydrogen in seawater?' I hear you ask. 'Theres any amount of hydrogen in water: H2O, see'.
So there is, but it takes a lot of energy to prise it away from the oxygen and due to thermodynamic inefficiencies, you will always get less energy out when you oxidise the hydrogen than you used to get it in the first place. The use of hydrogen in fuel cells is no different from winding a spring. You will probably end up burning something to wind that spring, too.

True, if you use electricity from sustainable sources it may be a very green spring but still an energy store, not an energy source.

Now, if you take the hard line that humans can use no more energy than is actually incident on the surface of the planet, then the only useful fuels are those derived from biosphere carbon (as opposed to geosphere carbon). Fuel cells can be designed to derive their hydrogen from methanol and its worth remembering that there is more hydrogen in a bucket of methanol than there is in a bucket of hydrogen.

Quixotematic looks forward to the day when the ENV or something like it is really available as an affordable personal transport option.

I have just stumbled across the Vectrix which fits the bill much better.