Guess I should explain further...
It's just not viable right now and the infrastructure and technology isn't there yet for this to become an efficient system for automobiles. You guys seem to think all you have to do is run a little current from solar energy and presto, you have hydrogen 'fuel'. And sure it produces more energy than gasoline when you disregard all the other required infrastructure around it. But the thing is, hydrogen has a very low density which means it occupies a larger volume per mass.
So yes, storing it is one of the biggest issues that needs resolving. In addition, when you store it, you only really have two options of storage, either in liquid form or high density gaseous form for hydrogen cars. Liquid form is out because you have to put in more energy to cool it in order to keep it at a liquid state. And high density gaseous state is extremely dangerous and leads to energy decay. You never really have pure water, unless you manufacture it. You have all these residual stuff that might be in there with the hydrogen and might react with it which gives you a loss of the 'fuel' so to speak. In addition, when you have it compressed like that, you increase the interactions going on inside losing the 'fuel' and creating a hazardous atmosphere for it. The only thing I'm aware of that has been proposed to resolve this storage issue is to create some mineral or something and have the hydrogen be latently attached to it in a somewhat stable state that is not likely to decay. The volumetric issue is very significant. Plus, due to its low density and the storage issue, lends itself to another problem which would be practicality. The method you guys seem to be presenting is oh water, lets make hydrogen. No, it's not as simple as that. The low density yield forces larger storage and you can't just do the whole electrolysis in every vehicle. You need fueling stations to do that. You can't do that in a vehicle because you'd need a large tank for practical travel and range capacity for the hydrogen and in addition, you'd need a huge water tank as well to generate all the hydrogen. Plus, you have the issue of decay if you just let the car sit there with hydrogen wasting away due to interactions and potentially devastating results. If the attaching to mineral thing pans out, then maybe there's potential for automobile applications.
Other issues involve some level of purifying water so you don't get decay, scarcity of water in certain regions, and with the solar, practical amounts of solar energy generation to drive the whole thing.
