I found this design on a site where the people used it for the Burning Man festival. They had it in their tent at night and said it worked like a charm! I plan to build one for my truck (no a/c) and either use the same one, or build another for our pop-up trailer. Unsure one unit could cool the trailer, so 2 may be required. I can also fill them with the ice cold water from the cooler each day. At $10 each or so, and a couple bucks a day for ice, it is a cheap way to stay cool!