Zeer Pot — A Fridge That Runs on Nothing

One clay pot inside another, wet sand between them. In hot dry air, it keeps vegetables fresh for weeks — no electricity, no moving parts.

At a glance

•      Origin: Kano State, northern Nigeria — Mohammed Bah Abba (1964–2010), teacher and clay-pot maker.

•      Maturity: Scaled — 5+ independent replications across multiple countries and climates.

•      Cost: roughly US$0.40–1.50. In Nigeria the pots sold for 40 US cents a pair.

•      Build time: 15–20 minutes to assemble. A child can build one.

•      Licence: Open — free for any use, no patent ever filed.

The story

In the late 1990s, more than 90% of villages in Mohammed Bah Abba's region of northern Nigeria had no electricity — no refrigeration, in temperatures that regularly passed 40°C. Tomatoes, peppers, and eggplants spoiled within two or three days of harvest, costing farming families their income, especially the women who sold produce at market.

Abba came from a family of traditional potmakers and drew on an ancient cooling principle known since at least 2500 BC: unglazed clay stays cool through evaporation. He combined it with a simple two-pot design — one pot nested inside another with wet sand between — to make an electricity-free refrigerator anyone could build from local materials.

He hired local potmakers to produce a first batch of 5 000 pots. To reach communities with low literacy, he even commissioned a recorded play by local actors to show how it worked. In 2000 he won the Rolex Award for Enterprise and used the entire $75 000 prize to scale it; by 2005 his organisation was making about 30 000 pots a year. He died in 2010, at 46.

A language note travellers love: “Zeer” is simply the Arabic word for pot — so “Zeer pot” literally means “pot pot.” It's in good company: the Sahara Desert means “Desert Desert.”

The problem it solves

Fresh produce spoils within two to three days in hot, dry climates without refrigeration — causing food waste, lost income, and poorer nutrition for farming families.

It matters most in hot arid and semi-arid regions with little or no electricity: sub-Saharan Africa, the Sahel, parts of the Middle East, and semi-arid South Asia — and especially for women farmers who must sell perishable produce quickly.

How it works

Put a 5cm layer of sand in the bottom of a large unglazed clay pot, set a smaller unglazed pot inside, and fill the gap between them with sand. Soak the sand with water, put food in the inner pot, and cover it with a damp cloth.

As water evaporates from the wet sand through the porous outer clay, it draws heat away from the inner chamber — the same physics that makes you feel cold stepping out of a pool. Re-wet the sand twice a day. That's the whole machine.

What to expect — and what not to

Tomatoes can last about three weeks instead of two to three days; leafy greens keep considerably longer too.

•      On a hot, dry day the inner pot typically sits about 8–12°C below the outside air — up to roughly 15°C cooler in the driest heat.

•      Needs a hot, DRY climate and good airflow — the drier the air, the better it works. Keep it shaded; direct sun overheats the outer pot.

•      Does NOT work in humid or tropical climates (above ~60% humidity evaporation stalls), in enclosed airless spaces, or for meat, dairy, or anything needing true-cold storage.

When it doesn't work — the honest part

The most common reason it underperforms is simple: humidity. People try it in the wrong climate and are disappointed. The honest rule is that this is a dry-climate tool — brilliant where it fits, useless where it doesn't. Check your local humidity before you build.

The other frequent failure is a glazed pot bought by mistake — glaze blocks evaporation and the cooling never happens. Wet a small patch before buying: on the right pot, the water soaks straight into the clay.

Credit & licence

Invented by Mohammed Bah Abba (1964–2010), Kano State, Nigeria — winner of the 2000 Rolex Award for Enterprise. Open, free for any use, commercial or not; no patent was ever filed. This entry documents the design as permanent prior art so no one can enclose it later.

The pot-in-pot has no central owning organization today — Abba died in 2010. Communities building one can point to open resources such as Practical Action's guidance.