(Low) technology
1. Evaporative cooling fridge with porous clay pot.
2. Filling of the inner layer with wet sand. It has a glazed inner container that prevents the liquid permeation and gives thermal inertia to the system.
3. Collection of rainwater or air condensation (day/night cycle).
4. The process is boosted by the chimney effect to increase the thermal difference down to 4ºC inside.

Prototype tested

1. Hypothesis: the action of air flow promotes the evaporation of water and therefore the cooling of the system.

2. Test: comparison of two hygrothermal meters (temperature and relative humidity).
– The first one inside a Pot in Pot (control).
– The second one inside another Pot in Pot with air flow. The air flow is generated by a fan and absorbed by a curtain to prevent the air flow impacting the control pot.

3. Result, hypothesis confirmed: joining a botijo with a chimney can achieve a passive fridge that only requires water to run.
– Control meter: dropped from 10ºC to 5.7ºC in 2 hours.
– Fan meter: dropped from 10ºC to 4.4ºC in 2 hours.

1. Prototyping of the autonomous BOTIJO refrigerator on a household scale.
2. Financing for pilot
3. Solution piloted in a real context, family with food and energy insecurity.
4. Publication of case study and analysis of results and costs.
5. Partnership with an NGO or cooperation agency to finance the first local production workshop.

Overview of the issue and your approach: Since it is not possible to store perishable products at the 20% of the worldwide homes, the population is forced to buy food daily in open markets, in which there is often no concern for hygiene, much less with maintaining them at suitable temperatures. That is, along with the problem of scarcity, there is also the consumption of food that can cause health damage.

Furthermore, the World Health Organization estimates that up to 50% of vaccines were wasted globally in 2021; largely due to a lack of temperature control and logistics to support an unbroken cold chain. At the scale of COVID-19, this rate of deterioration could have wasted about a billion vaccines, which, even when valued at a non-profit cost of about $10 per vaccine, represents a staggering wasted investment.

Due to these two reasons, passive coolers have already been developed:
- Pot in Pot, by Mohammed Bah Abba in Nigeria.
- Mitticool, by Mansukhbhai Prajapati in India.

The problem is that they are coolers, not refrigerators as they do not reach a temperature lower than 5ºC. Reaching 4ºC is a key milestone to avoid food spoilage as the lactic acid bacteria that cause spoilage multiply rapidly in food between 5ºC and 65ºC.

The BOTIJO is the first passive fridge that preserves medicines and fresh food (meat, fish, dairy products, greens, vegetables, etc) below 5ºC to avoid expiration in contexts where energy is scarce or insecure (frequent network outages).
The essence of your solution: By boosting the drying of the outer surface with an air flow, the chimney effect creates a current of air that speeds the water evaporation rate and therefore the clay fridge cooling.
The stakeholders in your project: 1. University or research center for the production and monitoring of the full-scale prototype. Alternatively, funding from the BETTER ENERGY BY DESIGN award to finance the team and resources.
2. Community that meets the objective selection criteria open to conducting a first pilot.
3. NGO or cooperation agency interested in the implementation of the first local workshop based on the results obtained from the project.