There is a lot of energy that is produced during the night, why not convert it to hydrogen? And with cheap solar panels there would be much more of the energy to convert it to hydrogen.
Surely, all of the above would take billions and billions. But what is the alternative? We need to get rid of oil before we run out of it.
The problem with converting to hydrogen is efficiency. There have been recent developments that vastly improve efficiency of the electrolysis of water using catalysts (to produce hydrogen), but it has yet to be commercialized. If that ever comes to market, maybe then hydrogen will be viable as an energy storage medium.
Right now, however, most commercial hydrogen production is done using fossil fuels - specifically, natural gas. However, as I said in my prior post to this thread, that means is actually more polluting than using gasoline - thus negating any perceived benefits.
And another thing that seems to be left out of the hydrogen equation is that its distribution (barring, of course, extremely efficient catalyst-based home conversion units) to vehicles. As I see it, that distribution would be very similar to the current gasoline distribution network, which, though many people never think of it, is itself very energy inefficient. It takes fuel to truck all that gasoline, as it would hydrogen, to market. Given that hydrogen is not the most stable of gasses, it might also be more dangerous to transport than gasoline.
I'm all for green energy, but the options need to be carefully considered lest humanity end up with an even worse solution and problem than we already have. Humanity tends to do stuff thinking its great, and then down the road, realizes "Hey, that wasn't a good idea. Perhaps we should have done something else."