Evaporative type air cooler mainly consists of energy efficient motor to rotate fan and water pump. It also consists of cooling pad. Size of cooling pad, fan, motor and cooler depends on quantity of cool air required per hour from cooler. Water pump pumps water on cooling pad and make it wet and at same time fan extracts air through pad and through on other side. Since air passes through wet cooling pad it gets cool. In New technology evaporative cooler or desert cooler are coming with great feature. New cooler are coming with control panel from which you can adjust fan speed, set timer, get alarm if water tank is empty etc.