In reply to The Norris:
The catch is that you need a hell of a lot of energy to electrolyse the water in the first place. Sure, one day in the future we'll have giant desert solar farms and everything will be just peachy, but right now this might not even make much sense even if you had a handy nuclear reactor to drive the whole thing.
Of course, given that this is a Naval Research Lab project, they'll have different economics to the rest of us (and are more likely to have a handy nuclear reactor).
Post edited at 08:19