**2. Natural refrigeration**

#### **2.1 Art of ice making by nocturnal cooling**

The art of making ice by nocturnal cooling is a common method of producing ice in India. It involves keeping a thin layer of water in a deep earthen vessel such as a tray with compacted hay of about 0.3 m thickness, which serves as an insulator, and as the tray was exposed to cool air, water emits heat by radiation to the stratosphere, almost at �55°C; the water in the trays turns to ice [9].

#### **2.2 Evaporative cooling**

The evaporative cooling method has been adopted in India for many centuries to obtain cold water in summer by storing the water in earthen pots. The water penetrates through the pores of the earthen vessel to its outer surface where it evaporates to the immediate surrounding, and absorb its latent heat from the vessel, which cools the water. In recent days, desert coolers are used in hot and dry regions to provide cooling in summer [10, 11].
