Evaporative cooling
Practical Action
The following basic materials are required to construct the Naya Cellar Storage:
1. Bricks -1200-1500
2. Sand - 400-500 Kilograms (880 Ib – 1100 lb)
3. Polythene hose - 6 meters (26’)
4. Water tank/bucket – 100 litre capacity (22 gal)
5. Bamboo/wood – 1.82 meters (6’) two pieces and 2.15 meters (7') two pieces
6. Straw - 2 bundles
7. Sacks
Construction details
Choose a small piece of land about 1.52 meters square (5'x 5') facing away from the sun or
where the sun does not shine directly. The ground should slope a little so that ground water
drains away and does not seep into the chamber.
The size of the cellar storage can be varied to suit the user. The greater the volume to be
stored, the bigger the size of the chamber. Normally, a 0.92x1.22 meters (3'x 4') rectangular
mortarless stone or brick structure is built to a height of around 1.22 meters (4').
A layer of sand, about 25mm (1") thick is, spread on the ground over the area where the
chamber is to be built and a layer of bricks or stones is laid onto the sand.
A doubled walled chamber is created from the bricks. The gap between the outer and inner
wall of the chamber is about 125mm (5"). The cavity between these two walls is filled with
clean sand. It should be free from soil to ensure against contamination from organic
impurities. A high-density polythene hose with pinholes made along its length is laid on the
sand within the cavity. The hose is blocked at the end so that water released from a tank
spreads through these holes and keeps the sand moist. A thatched roof supported by four
bamboo poles is placed above the cool chamber.
To keep the chamber cool, the circulation of air around the chamber must be unhindered. The
air around the chamber is cooled by the effect of the water evaporating from the porous bricks
and sand thus prolonging the shelf-Iife of the food stored within it. Sacks and bamboo sticks
are used to cover the chamber, which is kept moist by sprinkling water
Operation
To prevent damage to the fruit and vegetables they should be carefully stored in bamboo or
plastic mesh trays/baskets takes place. The trays/baskets have four legs so that their contents
are raised off the floor of the chamber. The flow of water through the hose needs to be
regulated in response to changes in the outside temperature to allow conditions within the
chamber to remain constant.
In one of the villages where Practical Action Nepal has been installing ‘Satso’ solar dryers, one
young mother also had a Naya cool chamber and was successfully storing cabbage and ginger
for up to 2 weeks longer than she had done without the chamber. She used locally available
stones from rivers to construct the walls, and covered the chamber with a piece of sack
mounted on a criss-cross of bamboo.
References and further reading
Evaporative Cooling - The Ceramic Refrigerator Technical Drawing
Evaporative Cooling - The Clay Refrigerator Technical Brief
Evaporative Cooling in Gambia Stories of Change
Evaporative Cooling in India Stories of Change
Cooling your cucumbers Appropriate Technology Journal Volume 24, Number 1 June
1997 page 27
Kitchen Trails, Food Chain, Number 18 July 1996, Practical Action
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