Air coolers are the 'Evaporation reduced heat' principle 

It uses cooling pads as an evaporator which not only reduced heat but also filters dust from the air to improve air quality 

Power 220v / 120w - Can be run off extension leads 

Not suitable for server rooms or sensitive areas where minuscule droplets of water can damage equipment.

Tank of 70 L water required. Does not require an exhaust system, just plug in and get cool. Great stand alone summer cooling system. 

Run time on full tank = 5 - 10 L per hour