There are different kinds of evaporative cooling systems single-stage and two-stage. They are available in various forms like evaporative air coolers, misting fans and misting systems, window and whole room based on its usability and capacity.
Evaporative air cooler which utilizes the natural process of using evaporation to cool the air. They are using a low wattage water pump to circulate water from the water tank on to three cooling pads, which in turn becomes very wet. fan draws air from outside the unit through the damped pads. As it passes through the pads the air is cooled by evaporation.