Rocket wrote:
> and the ammonia cycle can only pull a 40F delta, the inside
> of the refrigerator will eventually get to 60F.

Rocket's not goin' to give up on that 40 degrees!  That
number comes from the heat-exchanger devices such as
Koolatron. They specifically state the 40 degree limit:
http://koolatrononline.stores.yahoo.net/p9-traveller.html

As I and others mentioned, big RVs and houses all over the
world have gas fridges--with freezers.  RVs with gold
faucets in the bath like double-door fridge/freezers.

For your home or cabin, here is a 19 cu-ft fridge:
http://www.gas-refrigerators.com/propane/diamond/diamond-19-cubic-foot-propane-refrigerator.html
  Freezer alone is 4.7 cu-ft.

That site has a nice color diagram of the absorption cycle:
https://www.gas-refrigerators.com/

Nope, no 40 degree limit on the technology--if big enough.
Shrink the fridge and at some point before zero, you'll hit
40 degrees because the surface area and the volume converge
and any technology will work hard to keep the cool from
radiating away.  Bigger is better.

Richard