We have a trailer mounted generator at our gun club. I'm going to be the first person there if TSHTF. Also I'm going to liberate the cannon! Cause you never know when a cannon might come in handy in the apocalypse.
I'v helped build a couple of cold plate systems on boats. Key was insulation. We did one with about 6-8 inches of insulation all around, using top entry hatches (keeps cold in better). It ran off the engine or generator and took a couple hours to freeze up. Then if you limited opening the hatch to a few times a day it would keep things cold for about two days - in Florida.
I've long thought of building something similar into a house. It could power off solar pretty easily I think.