[seifrob]

I don't want to sound like a spoilfun here, but:

- energy stored in one scuba diving tank full of hydrogen sounds about right (back of envelope calculation though)

- iirc, you cannot electrolyse distilled water. You need to have some electrolyte (sulphic acid etc) to electrolyse. So there will always be both hydrogen and oxygene, but you can cope with it.

- it sounds like you are trying to make carbon free bussiness. Now, where are you going to take power to electrolyse and compress that hydrogen? Solar array? If that, you than need a real gas balloon, as you do not want few clouds to stop your bussiness. It adds to the bill

- if you are going to buy your electricity to power these electrolysers and compressors, than be ready to invest MUCH more kilowatt-hours in electricity to produce few kilowatt-hours in storage tanks. Its my wild guess, but I would say the ratio can be from around 6 to 1 to 12 to 1 (one kilowatt-hour in scuba tank will cost you six kilowatt-hours you pay in electricity). From financial point of view, this is disastrous. It would be better to buy loooong extension cords.

- If you want offshore emission free system with limited range, compressed air will serve you as well, with less hassle. You can compress your air using wind power. you can rebuild engines to run with compressed air. You can store compressed air in scuba tanks. you can refill it as easily as possible with compressors in case the wind stops blowing. They tested this in France in eighties, no more info though, but someone may chime in.