Thanks; and the big issue is that since hydrogen is the smallest molecule, over time it will seep through what ever the storage medium material is and make it brittle. even the most advanced materials will break down within a few years and start falling apart. So those fancy tanks you see used for storage will still breakdown after several years.The higher the pressure, the faster this will happen.
As to the efficiency; we were mainly working on proof of concept. A couple items that the efficiency is tied to is the electrode material and the electrolysis solution, we used standard carbon steel electrodes and many different solutions (lye is the bomb, but major caustic, be careful) oh, then the end of a 25 year marriage canceled forward progress on it, for the time being...
On 4th of July's we did have fun filling large clear garbage bags with hydrogen and attaching long fuses...
Then letting them go up over town, the concussion when it blew was the best...
This system still exists, sitting in my fathers barn right now.
The generator is on the right in the picture and the storage on the left.
The generator uses a "W" bin configuration, it also has dryers, filters and flow meters.
Right now I am building a HHO gas generator for one of my motorcycles. 30 sec burst, then let battery charge.
Should help the old 1980 kz750 twin do some street fighter gigs at the lights still ;)
The 1994 CB1000 is getting a turbo next :)