You see refrigerators that are propane/electric or both but use the ammonia/water cycle to produce a chill. You make heat to boil off the ammonia(I think it's

You see refrigerators that are propane/electric or both but use the ammonia/water cycle to produce a chill. You make heat to boil off the ammonia(I think it's 60C) and then hold that in a vessel and let it recombine as needed. Ammonia is hydrophilic and the reaction of them is endothermic. There are a lot of ways of getting heating to 60C and doing this. I have always thought that a system could use evacuated solar tubing to generate the heat.