Innovation often springs from necessity, and three teenagers from India have demonstrated exactly that with their ingenious solution to a serious healthcare challenge in rural areas.
Faced with the difficulty of transporting vaccines and medical supplies to remote villages in sweltering tropical heat, these inventive students set out to create a refrigeration system that requires no electricity, no batteries, and no chemical coolants. What they developed could have a meaningful impact not just in their home country but across the world.
The device, which the trio named Thermavault, uses a clever natural reaction: the cooling effect produced when certain salts dissolve in water. No cords, no compressors, no fossil fuels — just the natural science of thermodynamics at work.
Calling it “a fridge to bridge the world,” the Thermavault can achieve different cooling temperatures depending on which salts are used. Some vaccines, for example, require regular refrigeration temperatures similar to a kitchen fridge, while others — as well as critical materials like transplant organs — need to be kept below freezing.
The ability to customize the cooling range gives the Thermavault a significant edge for healthcare delivery in areas where reliable electricity remains a challenge.
The three inventors — Dhruv Chaudhary, Mithran Ladhania, and Mridul Jain — are all children of doctors and medical workers in the Indian state of Indore. Throughout the COVID-19 pandemic, they witnessed firsthand the struggle to keep vaccines cold during long journeys to countryside clinics, often hours from the nearest city center.
Determined to help, they tapped into a basic scientific principle they’d learned about in school: when salt dissolves in water, its molecules break apart into charged ions. This process requires energy, which it draws from the surrounding water in the form of heat, thereby cooling the water down.
Though the team understood the basic concept, the challenge lay in finding the right combination of salts that could deliver the necessary cooling effect for long durations. Contrary to what most people assume, sodium chloride — everyday table salt — isn’t the only kind of salt. In fact, there are more than a hundred chemical compounds that classify as salts.
“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 admitted in an interview with Business Insider.
Working alongside professors at the Indian Institutes of Technology (IIT), the students tested over 20 different salts before identifying the most effective options: barium hydroxide octahydrate and ammonium chloride. On its own, ammonium chloride could chill the water to between 2°C and 6°C (35°F to 43°F) — an ideal range for many vaccines.
By adding a small amount of barium hydroxide octahydrate, the team could push the temperature even lower, creating conditions suitable for storing materials that require freezing.
The Thermavault has already been trialed in local hospitals. “We have been able to keep the vaccines inside the Thermavault for almost 10 to 12 hours,” said Dr. Pritesh Vyas, an orthopedic surgeon at V One Hospital in Indore, who tested the prototype said on the Thermavault website.
Encouraged by these promising results, the teens are now preparing to build an additional 200 units to be tested across 120 hospitals around Indore. This extensive testing phase will help gather valuable data on how the Thermavault performs under different conditions and inform improvements ahead of a potential large-scale rollout.
Their invention recently earned them the prestigious 2025 Earth Prize, an international award celebrating environmental solutions developed by students. Along with the recognition, the team received a $12,500 prize to help fund the production of more prototypes and expand testing efforts.
What began as a high school science project could soon become a vital tool for improving healthcare delivery in some of the world’s most underserved regions. The Thermavault’s low cost, simplicity, and versatility make it a potentially life-saving innovation — and a remarkable example of what young minds can achieve when driven by compassion and curiosity.
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