A 'zeer' refrigerator

A POT IN A POT

- Master Kshitij Kadam (Std. VII A)

St. Joseph's High School,
Wadala,
11th December 2013


The Science Exhibition held annually by the Education Department presents an opportunity to our budding scientists to create, experiment and innovate. Four of our students from Std. VII (Kshitij Kadam, Ayush Kamble, Yohan Mhatre, Anirudh Bhattacharya) have designed a 'pot in pot' refrigerator or 'zeer' (in Arabic) pot fridge.   It is an evaporative cooling refrigeration device which does not use electricity. It uses a porous outer earthernware pot, lined with wet sand, and an inner pot (which can be glazed to prevent penetration by the liquid) within which the food is placed - the evaporation of the outer liquid draws heat from the liquid. The device can be used to cool any substance.

The 'pot in a pot' cooling system, a kind of 'desert refrigerator', helps subsistence farmers by reducing the food spoilage and waste, and thus increasing their income and limiting the health hazards of decaying food. This device consists of two eartherware pots of different diameters, one placed inside the other.  The space between the two pots is filled with wet sand that is kept constantly moist, thereby keeping both pots damp. Fruits, vegetables and aerated drinks are put in the smaller inner pot, which is covered with a damp cloth.

A few examples of its effectivity:

- Tomatoes and apples lasted for three weeks or more.
- Green plants stayed fresh for 27 days instead of three.
- African spinach that usually spoils after a day, remained edible after 12 days when placed in the 'zeer' pot fridge.

Harvesting today means selling today:

1. Lack of electricity in most of the northern rural communities - without electricity there can be no           refrigerator.

2. The towns and cities too have erratic power supply that affects the refrigerator.

3. In an agriculture based populated area, the majority of people live in abject poverty to afford a refrigerator.

Hence a 'pot in pot' can grow popular and be marketed judiciously for its huge benefits:

1. Simple and effective use of the laws of thermodynamics.

2. Cheap and easy to build.

3. Needs simple innovation that can drastically change the lives of the poor.

4. It is a great way for those of us looking to live off the grid to keep some of the organic foods fresh for longer periods.

Time to innovate and live simple!