I think the energy source has to be a battery. Also you need DC for electrolysis, so a battery fits - no messing around with invertors and rectifiers and the associated losses. And if the claim to be 100% green has to be true, then the battery bank has to be charged by solar cells. 

Just going back to an earlier post of yours - "They mentioned again in that video "with 2 litres of water you can product up to 1MW per week".  If you break that down to kWh at 168 hours per week, you get 5.95 kWh. Allowing for efficiency loss on the separation and power generation  sides, 5.95kWh from 6.6kWh is believable. So it's 2L of water a day, not 2 litres of water."

How did you get 2L of water per day? Shouldn't it be 2L per hour.

Brgds - AG