OK - Sorry about this. But I just can't contain myself any longer. The whole hydrogen economy thing is STUPID, until somebody can show me their hydrogen well or hydrogen mine. Here on earth, you have to strip hydrogen away from carbon or oxygen. And that requires energy input from some other source. Furthermore, taking hydrogen away from a bio - or petro compounds still leaves you with CO2. So what does that gain? To hydrolyze water, you may be able to use solar power. IIRC solar power at 100% efficiency at high noon today (the soltice) is about 1 kw/m2. At real world efficiencies and year-round insolation rates it would take a lot of m2 for that idea to work.
Now, - off my soap box. Ned Kleinhenz '95 E300D x2 '85 300D '80 300TD