If you are in a hot dry area, like Arizona or Nevada, then a swamp cooler can be your friend. Swamp coolers are not much use in humid weather. Swamp coolers are perfect for Burning Man. Here is a good instructional video.
Swamp coolers do not need a lot of power, since they only involve moving air. A relatively small solar panel should cover your needs. Here is a nice and thorough instructional blog post from the good folks at Playa Labs.