Habibunnisa (1988) fabricated a metallic EC chamber measuring 45×45×45 cm (approx. 0.1 m3) with a 2 mm GI sheet with the top side open. The four sides of metallic chamber were covered with a cloth, the top ends of which were immersed in water placed in the top tray. For allowing evaporation, the cloth surrounding the metallic chamber was made to remain wet continuously by downward gravitational flow of water. A wire mesh basket of size 30×30×30 cm filled with fruits was kept inside the chamber, leaving adequate space all around the basket for circulation of the air. The EC storage increased the shelf life of apple by 6 times and mandarins by 4 times.
Rama (1990) studied the relative performance of two models of EC storage structures with regard to their efficiency in maintaining the temperature close to the ambient wet bulb temperature and high RH. The first structure was the same as that used by Habibunnisa. The second one resembled the first one except that the outer metallic wall was replaced by a weld wire mesh (2.5×2.5 cm) with evaporative sides covered with wet gunny cloth to help in free movement of evaporatively cooled air. The top tray used in this system (to serve as the water reservoir to wet the gunny cloth) was devoid of vents. The inside temperature for both the systems were almost similar and close to the ambient wet bulb temperature and the relative humidities were 90±5%, respectively. The lower RH of the system 2 was attributed to the free air circulation through the structure.
Sharma and Kachru (1990) used evaporatively cooled sand stores, where a 5 cm thick potato layer was placed on floor in between two sand layers each of 20 cm thick. In order to allow evaporative cooling, 2.1 m3 of water was sprinkled daily to wet the sand. It was observed that under low atmospheric RH conditions, wet sand was suitable for storing potatoes for up to 90 days as compared to 60 days in jute bags and still less in other storage methods like bamboo baskets and heaps.
Roy and Pal (1991) developed a low cost zero energy cool chamber—an on-farm rural oriented storage structure at IARI, New Delhi, using locally available raw materials such as bricks, sand, bamboo, dry grass, jute cloth etc., which operates on the principle of evaporative cooling. The chamber is an above-ground double-walled structure made up of bricks. The cavity of the double wall is filled with riverbed sand. The lid was made by using dry grass/straw on a bamboo frame. The rise in relative humidity (90% or more) and fall in temperature (10–15 °C) from the ambient condition could be achieved by watering the chamber twice a day. Performance evaluation of cool chambers at different locations of the country was found to be satisfactory for short term storage of mangoes. Eventually, 3 to 4 days more shelf life of mature green mangoes could be obtained in cool chamber storage as compared to ambient condition storage. However, ripe mangoes when stored in cool chamber had 9 days shelf life as compared to 6 days under ambient condition and also scored high organoleptic values. It is most effective during the dry season.
Umbarkar (1998) constructed an EC structure of 2 tonne capacity based on the results of their previous studies. The walls of the structure were constructed with 10 cm thick brick batt pad sandwiched between two 10 cm thickness brick perforated walls. To add to the structural strength, 8 mm diameter mild steel reinforcement anchored the latter with each other. Holes of 50×40 mm were provided between two successive brick layers for air circulation throughout the height of the structure. A thatched roof with bamboo mat and dry grass was provided as cover at the top. At the bottom of storage stacks, a free board of 10 cm was left for bleed off water from walls. The temperature in the chamber varied between 23 and 26.5 °C as against ambient temperature variations between 25 and 44 °C on a test day. The relative humidity in the structure was 85–97%. The water requirement was 325 litres per day.