[ziggytrix]

Doesn't get much cleaner than water vapor for exhaust. They're just not practical yet, I think as it takes energy to produce the Hydrogen that fuels the car.

Pluse there's the whole Hindenburg problem. That much hydrogen in one place is a bit tricky to manage. I think they compartmentalize it to reduce the possibilty of it all exploding at once in a crash, but that adds weight, so there's another problem.

Problems >> benefits at this stage in development. Of course I'm prolly years behind the times on this.