Nothing to do with radio, but thought I'd mention it because it's so cool and it's pretty silent around here, so why not. I'm always interested in any type of off-grid devices and this is certainly one. I remember reading something about how they used to keep food fresh in the desert thousands of years ago, and I guess perhaps this passive refrigerator invention is based on the same principle..
How a village potter invented a refrigerator that works without electricity: What makes it so ‘cool’
.... .. Mansukhbhai Prajapati, a potter from Gujarat, built a clay refrigerator that runs without electricity and uses a simple principle older than modern appliances: evaporation. .... The story began after the 2001 Gujarat earthquake, when Prajapati saw the vulnerability of families who had lost homes, power, and the basic means to preserve food. ...
he spent nearly four to five years experimenting with different clay mixtures before arriving at the right formula. By adding materials such as sawdust and sand, he made the clay body porous, allowing water to slowly seep through the surface and evaporate. As the moisture evaporates from the outer walls, it pulls heat away from the inner chamber, creating a natural cooling effect—without compressors, coils, or any electrical input.
The National Innovation Foundation describes the refrigerator as a natural refrigerator made entirely from clay, an idea refined through years of trial and experimentation. ... the solution feels deeply rooted in the specific conditions for which it was designed and created. In a nation where relentless heat, frequent power cuts, and the challenge of affordability are everyday realities faced by countless families, ..
I don't know how useful this would be. India? Temperature is 40 C(104 F) and higher and it can be 8 C cooler inside that would be 32 C(90 F). Not much of a refrigerator.
The best is what we did in the 50s and before when everyone didn't have refrigeration you had an ice box....a very well insulated compartment and you went to buy ice at the corner store or in winter ice was taken from outside or frozen lakes to fill the icebox and you had real refrigeration. You had a place to catch the water as the ice slowly melted.
@mark It's intended as an emergency item for situations where you're not going to have access to electricity or ice or modern conveniences for extended times.
"... The National Innovation Foundation says the refrigerator works on evaporation and can keep fruits, vegetables, milk, and drinking water fresh for two to three days. It also notes that the device performs best in hot, dry climates, where evaporation is strongest. In practical terms, it offers a cooling gap of roughly 5–8°C below outside temperature.
Why it mattered to ordinary households
Conference on Trade and Development has pointed out this innovation as a quintessential illustration of what is termed "frugal innovation," emphasizing that it is available for purchase at a price point of less than $50 and possesses the remarkable ability to keep food fresh for durations ranging from two to three days..."