Hydrogen storage is a problem, high pressure tanks are very dangerous and need a lot of maintenance nad safety checks. On-demand hydrogen is very, very difficult to produce at such a high rate. I believe combining a system of stored hydrogen and hydrogen production will give us good results.
Odd that no one mentioned metal hydride storage so far. It's relatively safe, not stored under pressure, can't explode on you, etc. And it stores 4x more hydrogen per unit of space than liquid hydrogen. 4x Liquid storage, in the same space That's pretty hard to beat, seeing as the other alternatives are several very large hydrogen-producing cells, or high-pressure tanks, which virtually guarantee an explosion in an accident. Even a small leak from a tank, and a spark (easy enough to get) are a huge, huge problem.
