How does an evaporative cooling system work?

The heart of an evaporative cooling system is the pad where the water evaporates.

This pad is manufactured of fluted cellulose sheets that are glued together. This material is chemically impregnated with special compounds to prevent rot and ensure a long service life.

A special water distribution system spreads water over the surface of the pad, ensuring a uniform supply of water to keep the entire air contact surface thoroughly wetted.  

Fans on the opposite wall of the building create a negative pressure inside the building, causing air to be drawn through the pads.

Evaporation results from contact between air and water. A control system operates the water pump and turns the fan(s) off and on.

On a hot sunny day, the moisture content of the atmosphere remains virtually constant.  This means that the relative humidity is lowest in the afternoon when the temperature is at its highest.  And the lower the humidity, the better the evaporative cooling effect.  In other words, the cooling effect is best when you need it the most.