Utilises the capacity of certain substances to adsorb water on their surface, from where it can be separated again with the application of heat - dry air is obtained. If this dry air comes into contact with water it again absorbs water vapour.

The evaporation of new water produces a cooling effect. The adsorptive medium afterwards may be dried with solar heat, coming from cheap "hot air" collectors. The machines are heavy and big. Refrigeration below 0°C is not possible.

Adsorption cooling with a "closed cycle" is possible too.