Air conditioning may seem like a luxury, not a necessity, but some studies have shown that productivity increases dramatically if workers do their jobs in cooler spaces. What does that say about places such as Brazil and India, where just 11 percent and 2 percent of households, respectively, have air conditioning [source: Rosenthal]? It says that people living in developing nations will need A/C as much as they need clean water and better access to health care.
Most of us think of units filled with refrigerants, especially chlorofluorocarbons like Freon, when we think of air conditioning, but some cooling systems work on a different principle. Evaporative coolers, also known as swamp coolers, take advantage of water's ability to change from a liquid to a gas. Heat is required for this state change to occur, so if you can get water to evaporate, you can cool something down. Swamp coolers do just that by blowing dry, hot air over a moist fabric. As the hot air encounters the fabric inside the unit, it evaporates the water, losing some of its heat in the process. A blower then forces cool, humid air out into the room.
You can build a homemade swamp cooler using a cooling fan from an old computer, wooden craft sticks, an absorbent cloth and a small, 2-watt solar panel for power. First, you create a frame out of the craft sticks, with the fan supported at the top so it blows down and two decks below the fan to support strips cut from the fabric. Everything should be glued so the structure stands upright and sturdy. Then you connect the wires from the fan to the solar panel (or batteries as a not-so-green alternative), wet the fabric and let the cooling begin.