I was thinking about building a gasometer to run my RV fridge and I had the thought why not displace the water instead of a vessel? This way you can take advantage of the water weight to compress the gas bit to get more energy density pr charge. It would still be relatively safe. (I would never ever consider or endorse pressurizing hydrogen or CO in a sealed container ever.)
So here is what I am considering building. Using one 16 gallon 14 inch diameter barrel drum and a 55 gallon barrel drum. The 16 gallon if it has an open top removable lid you simply invert it and will need to lock in place a few inches above the bottom surface of the 55 gallon drum. Then you have an inlet / outlet placed at the top of the 16 gallon inverted drum.
Ok so if my figuring is correct. 16 gallons you multiple by 2 giving 32 gallons. This is the static water displacement that will do nothing. So this leaves 23 gallons of water of the 55 gallon drum that can actually be displaced. One gallon of water weighs 8.34 so 23 gallons X 8.34 = 191.82 lbs of gravity force. So this will allow some pressurizing of the gas but still with a way to vent out in the case of a flashback and it should only displace the water shooting out. So you would not have a vessel flying through the air. lol If were a really potent flash back that would over come displacement of the water, the 55 gallon drum itself I think would be plenty sufficient to shield it from harming anything.
Off grid refrigeration is only real difficulty in going off grid. Electric refrigerators require a lot of energy. However an LP Fridge is very efficient and I think you could easily run and sustain a large size RV LP refrigeration unit using this contraption.