Is your AC costing too much to run? Is cost of solar or geothermal prohibitive? Maybe an evaporative cooler is an option for you. Evaporative coolers, or swamp coolers, are relatively simple devices. Operation cost are limited to a water (3-20 gallons a day), limited electricity for a fan and limited electricity for a water pump. Operation costs could be a little as a fourth of what it costs to run the AC.
They can cool the air by 15-40 degrees by means of the heat exchange between air and water when moving air is passed through evaporating water. When the air passes through, it also absorbs some of the water. This can be good in extremely dry climates, as the added humidity can reduce static in the air. They also require outside air to work, so they provide a constant stream of fresh air.
Because they rely on the heat exchange between air and water, they become increasingly less effective as the humidity increases (they work best in dry climates). Care must be taken as the use of water can lead to moisture problems, including mold, if not well maintained. In cold months, the water lines must be protected from freezing.