Salt-Powered Ref Invented By Three Teens

There are three teenagers who just designed a mini refrigerator that cools itself with salt and doesn't require an outlet. They're bringing it to hospitals to help transport medical supplies to rural areas without electricity.

Dhruv Chaudhary, Mithran Ladhania, and Mridul Jain live in Indore, India and all have parents working in medical fields. The boys decided to find a salty refrigeration technique after hearing how challenging it was to bring COVID-19 vaccines to rural areas without electricity.

Their invention, which they call Thermavault, won them the 2025 Earth Prize on Saturday. The award comes with $12,500, which they plan to use to build 200 of their refrigerators and send them to 120 hospitals for testing.

They hope their refrigerator can help transport vaccines, other medicines and supplies, and even transplant organs.

"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, says in a video on the Thermavault website.

With some improvements like a built-in temperature monitor, he added, "it will be definitely helpful, definitely useful in the remote places, the villages."

Some salts can have a cooling effect when they're dissolved in water.

That's because when those salts dissolve, the charged atoms, or ions, that make them up break apart. That separation requires energy, which the ions pull from the environment, thus cooling the water around them.

Chaudhary, Ladhania, and Jain searched the internet, first compiling a list of about 150 salts that might work, then narrowing it down to about 20 that seemed most efficient.

They then borrowed a lab at the Indian Institutes of Technology to test those 20, or so. To their disappointment, none of the salts cooled the water enough.

They were back to square one. Turns out, they didn't need the internet after all — their school teacher recommended trying two different salts: barium hydroxide octahydrate and ammonium chloride.

"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 said.

The trio says they found that ammonium chloride maintained temperatures of around 2 to 6 degrees Celsius (about 35 to 43 degrees Fahrenheit), which is ideal for many vaccines. Adding barium hydroxide octahydrate to the mix produced sub-zero Celsius temperatures, which is ideal for some other vaccines and sometimes for transplant organs.