Cooling can be broken down into 3 areas:
Extract the warm air from a room to the outside using a duct.
Attach the flexible air hose to the unit. The other end of the hose needs to be placed out of the room, through an open window or door.
Cool an area by gradually introducing water to the air creating a similar cooling sensation as felt when walking by sea on a hot summers day.
An evaporative cooler has a tank that is filled with water. This soaks a rotating membrane. A fan pulls air through this membrane. The water evaporates and this is how the air is cooled. These types of coolers work best where there is a constant supply of fresh low humidity air.
Bring a sensation of cooling but do not actually cool the air.
BTU stands for British Thermal Unit. It is a traditional unit of heat, measured using the old imperial measuring system. In simple terms it is the amount of heat or cooling required to change a unit of water by one degree Fahrenheit.
KW stands for Kilo Watt and is the more modern metric heat and cooling measurement.
There is a direct relationship between BTU and KW.
1KW is the equivalent of about 3400BTU which means a 9000BTU machine is the same as a 2.6KW machine.