Admittedly I have not studied the ammonia cycle in sufficient depth to understand it the way Mr. Squirrel has.  However, if it can only cool to 40 F below ambient, how is it that it was used to make ice in Texas and other hot places for decades?  The ammonia cycle has been the refrigeration mechanism of choice in the frozen food industry, ice making, and a great deal of other refrigeration applications since the nineteenth century.  I realize that there might be the possibility of pre-cooling by other means, and I have not investigated more than superficially how large plants go about removing heat.  But the ammonia cycle is of widespread application and has been for a very long time.  You cannot make ice unless you can get below 0 C, 32 F.

David McNeely