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Zimbabwe pupils’ non-electric fridge invention a winner

Zimbabwe pupils’ non-electric fridge invention a winner

Jul 29, 2014

By Knowledge Chikundi
START Science Zimbabwe Leader

It was all joy on 11 July 2014 when the Queen Elizabeth Girls students scooped the first prize at the SEITT Young Scientist competition in Harare. Their invention was very outstanding and novel.

Under the supervision of the University of Zimbabwe START Science Programme, Queen Elizabeth Girls High School students have come up with a lasting solution to the perennial problems associated with food wastage in Africa.

Here’s what, Nomathemba Nyoni, the team representative had to say:

“Food preservation is a critical problem in most developing countries. Many methods have been devised, but very few have had a real impact on these commonly poor societies. Our concept tries to create a lasting solution to perennial problems associated with food preservation using the cooling method. I have devised a refrigerator which makes use of powder coolant made from a mixture of food waste ash powder, lemon juice and anhydrous ammonium nitrate. The present project combines an endothermic reaction, vacuum technology and a programmed chip to bring refrigeration to every home.

“The reaction of the powder with water is very endothermic; it reaches negative 9 degrees Celsius at normal room temperature. With very cheap lagging the temperature has been kept constant, and to only rise to positive 9 degrees Celsius after 10 days.
It is the further object of this project to apply vacuum technology to keep the temperature low for extended periods.”

It is the search for new applications of technology to present food wastage crisis that has led to the our interest in connected technologies and to the project we are currently supervising at Queen Elizabeth Girls High School. People in marginalised communities have problems saving their food; they are forced to cook more than they can consume. They have limited ways of preserving their left overs.They cannot afford the conventional refrigerators which are expensive and require electricity. It is my hope that the present project will alleviate most of the problems regarding food preservation.

All the technologies to be applied are already cheap and local, making the project more feasible. A lot has been achieved from the time the idea came. All the testing has been done; laboratory test certificates are available as confirmation. The testing and design stages are over; the prototype is currently being refined. The project is going at a very high momentum.

I am very impressed by the creative genius of the students. The project is very revolutionary. There are many different types of refrigeration technologies, but the current one will impactfully address Africa’s need, in food security and environmentally.

In the prior art, refrigeration is accomplished by the use of heat pumps. There is the compression refrigerator which uses coolants such as ammonia, Freon, CFC and HCFC. However all these coolants destroy the ozone layer and ammonia is toxic. A gas refrigerator uses water, ammonia gas and hydrogen to create a continuous cycle for the coolant. Electric coolers use the Peltier effect to produce cold temperatures electronically.

The present refrigerator uses a coolant powder which is consumable and recyclable. Embedded inside the refrigerator is a small- battery powered thermoswitch which signals when the temperature reaches positive 9 degrees Celsius. 9 degrees Celsius is the set point for replenishing. When the switch signal, the user is supposed to refill the coolant powder. The used powder can further be used as fertiliser.


  1. Amram /

    Great innovation for Africa! I have faith in Africa and its future.

  2. Louise Sawyer /

    Would have loved to know the student’s name, and to have seen a picture of her. Would have loved to have heard from her. What was her process? What were the other entries?

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