It is simple, all you do is put an external thermostat on it with a temp probe that goes into the freezer. Apparently they only run several minutes per hour and are much quieter than a reg. fridge. One problem is that it is much harder to organize and get to things in it.
Go to this site, and go to refrigeration.
Backwoods Solar Electric Systems
I think there was a guy in australia who also did this. would have to search for the link.