I am all for DIY and experimentation and so on. But if you want reliable, easily useable/no-brain-damage food refrigerating and freezing, you just can't go wrong with electric appliances and photovoltaics. Well, if you don't have a pv system set up already, don't read further. But if you do, it is trouble-free. We've been in our off-grid home since 1985, and after a few years I gave up and bought a 12 v. fridge and never looked back. Zero trouble or repairs since then. In fact, three yr. ago I added a 12 v. freezer and we love it. Again, zero trouble. Very efficient and you plug them in and forget them.
A friend of mine near Santa Fe, NM has a propane fridge with a freezer compartment in it. He spends too much [I think] on propane and the freezer part doesn't work all that well. The thing does work, however, and keeps his stuff cold. I am just allergic to spending so much money on propane. He has 12 v. pv running the rest of his home but he is allergic to spending money on an electric fridge [his propane fridge cost him next to nothing when someone wanted to get rid of it]. However, he has, after some years, passed the point where his propane bills are more than the cost of an electric.....