Teen innovators build saltwater-powered fridge that is changing the world

www.americaoutloud.news ^ | April 27, 2025 | Jimmy Hinton

[Red Badger]

A digital mockup of a Thermavault – credit, Dhruv Chaudhary, Mithran Ladhania, and Mridul Jain, supplied From India comes the story of three teen inventors who were looking to improve rural healthcare by creating a portable fridge that needed no electricity or coolant fluids.

The result of their inspiration is a small, salt-cooled fridge that needs neither a power outlet nor a battery, but rather cools down passively as the salts dissolve in water.

Calling it “a fridge to bridge the world,” the Thermavault can use different combinations of salts to keep the contents at temperatures just above freezing or below it. Some vaccines require regular kitchen fridge temps, while others, or even transplant organs, need to be kept below freezing, meaning this versatility is a big advantage for the product’s overall market demand.

Dhruv Chaudhary, Mithran Ladhania, and Mridul Jain are all children of physicians or medical field workers in the state of Indore. Seeing how difficult it was to keep COVID-19 vaccines viable en route to countryside villages hours outside city centers in tropical heat, they wanted to create a better, portable solution to keeping medical supplies cool.

Because salt molecules dissolve in water, the charged ions that make up the salt molecules break apart. However, this separation requires energy, which is taken in the form of heat from the water, cooling it down.

Though the teen team knew this, it remained a challenge to find which kind of salt would have the optimal set of characteristics. Though sodium chloride—our refined table salt—is what we think of when we hear the word “salt,” there are well over one-hundred different chemical compounds that classify as salt.

“While we did scour through the entire internet to find the best salt possible, we kind of just ended up back to our ninth-grade science textbook,” Chaudhary told Business Insider.

Indeed, the professors at the lab in the Indian Institutes of Technology where they were testing Thermavault’s prototype were experimenting with two different salts which ended up being the best available options, a discovery made after the three teens tested another 20, none of which proved viable.

These were barium hydroxide octahydrate and ammonium chloride. The ammonium chloride alone, when dissolved, cooled the water to between 2 and 6 degrees Celsius (about 35 to 43 degrees Fahrenheit) perfect for many vaccines, while a dash of barium hydroxide octahydrate dropped that temperature to below freezing.

“We have been able to keep the vaccines inside the Thermavault for almost 10 to 12 hours,” Dr. Pritesh Vyas, an orthopedic surgeon who tested the device at V One hospital in Indore, said in a video on the Thermavault website.

Designing a prototype, the teens have already tested it in local hospitals, and are in the process of assembling another 200 for the purpose of testing them in 120 hospitals around Indore to produce the best possible scope of use and utility data for a product launch.

Their ingenuity and imagination won them the 2025 Earth Prize, which came with a $12,500 reward needed for this mass testing phase.

[BobL]

Cheaper to drop a generator, a Jackery, and some fuel (or solar panels), instead of 50 lbs. of salt every day.

[ProtectOurFreedom]

I'll bet they could make some good ice cream with that invention!

[Codeflier]

That’s what I thought of immediately. Been done for a long time!

[yesthatjallen]

A portable cooler with dry ice would be cheaper and produce no chemical waste.

[GMMC0987]

This idea is only several thousand years old.
The pot in pot refrigerator or Zeer.

https://en.wikipedia.org/wiki/Pot-in-pot_refrigerator#:~:text=A%20zeer%20is%20constructed%20by,evaporate%20effectively%20towards%20the%20outside.

[null and void]

So it’s a bit like a gas refrigerator, but you use the salts once and then throw the brine out and buy more salts?

[E. Pluribus Unum]

[Bigg Red]

mark

[House Atreides]

Yep… that was my first thought also. Just another application of a VERY old idea.

[digger48]

Boat beer cooler

[_longranger81]

How different is this from a chemical cold pack where you break a glass vial and mix it around?

[ProtectOurFreedom]

Different principle. The “pot in pot refrigerator” or Zeer uses evaporative cooling. Evaporation requires energy (in the form of heat) to change the liquid into a vapor, drawing that heat from the environment or the remaining liquid, thus lowering the temperature.

[Scrambler Bob]

Can you dry out the salts and use them again?

[GenXPolymath]

“Can you dry out the salts and use them again?

Yes absolutely salt dissolved into water, is endothermic you can reverse this by heating the brine and paying the energy debt needed to fuse the salt back to its original ionic bonded form. Cool it to room temp and add more water the process should be reversible thousands of times. Rural and disaster areas will all have something to burn under the used pot of salt water this is the true utility of this.

[Colorado Doug]

Yeah, they may be good at that sort of thing but but I’ll bet they can’t name the 97 different genders like American students can.

[Red Badger]

Yes....................

[Red Badger]

BUT CO2 that dreaded pollutant!.......................

[know.your.why]

Here the boys are 'splaining how it works. I still dont get how its electricity free:

https://www.youtube.com/watch?v=YhhI-WQWBsI

[norwaypinesavage]

It’s hard to make ICE cream when your coldest temperature is 35 F. ICE cream needs to get below 32 F.

This idea is great for a temporary situation, likely less than a day. It requires significant quantities of barium hydroxide octahydrate or ammonium chloride - not exact something just sitting around in your kitchen cabinets.