In dryer climates such as in the southwest, you do not need the ice to get air conditioning
without refrigeration. Evaporation can cool it down pretty well, very well if it very low humidity. We are still using an evaporative air conditioner at our home in Las Cruces. But have gone to the second generation of them, such as Master Cool which uses just one thick pad on one end instead of 3 or 4 on the sides. In the '70s & maybe the '80s an evaporative a/c for auto use could be bought at JC Whitney, I believe. A friend had one on top of his suburban. Had to carry water to replace what evaporate from time to time. Would not work in Florida I am thinking, just add to the humidly in the egg. I have seen some small window units in Travel Trailers in the past, older units.
When googling Mater Cool I found something interesting and maybe more on tract with the topic. A Waterless Air Cooler! If it works, I do not have a clue. I see it is using the ice as coolent agent: uses two large gel ice packs. Advanced HD-Ice gel packs use a high-density gel. Each gel pack offers more cooling capacity than conventional ice packs.
Evaporative still better, IMHO. Nothing to freeze. Here's what the new generation units look like:
They do make portable swamp coolers: http://www.lowes.com/lowes/lkn?action=prod...&lpage=none
Not sure were to put it in the egg, maybe in the bathroom pointing into the trailer.
Looks like I went off on a tangent, now to come back on target somewhat. Using the basic evaporative as coolant idea, one can cool an area down by weting a towel; hanging it over an open window (I would hang it outside) & have another window open with a fan drawing air out of the trailer. They cool green houses in our part of the world doing the same thing. Not a wet towel, but wet pads on one side of the green house and fan on the other pulling the air out. Rig up a window washer kit to spray water on the towel when it dries. Or better yet hang a collapsible water bottle set at a slow dip to keep the towel wet, maybe with a tube running along the top edge of the towel with holes to make it a soaker hose.
Yup! It would work. It might
even work in Florida (?), if one could sleep in the direct path as the air is coming in off the towel. They sell 12v fans which plug into a cigarette lighter.
It should work to keep a dog crate cool as well, perhaps using an electronics fan or a small RV fridge