Three teenagers from Indore, India — Dhruv Chaudhary, Mithran Ladhania, and Mridul Jain — have developed a self-cooling mini fridge called Thermavault, powered by salt instead of electricity. The invention was inspired by their families’ involvement in the medical field and the challenges faced during the COVID-19 pandemic in transporting vaccines to remote areas lacking electricity. Their salt-powered fridge uses a chemical process where salts absorb heat when dissolving in water, effectively cooling the interior without external power.
Reinventing Cold: Salt-Powered Innovation Behind the Thermavault
Initially, the team researched 150 potential salts online, narrowing it down to 20, but none were effective. A teacher then recommended trying barium hydroxide octahydrate and ammonium chloride — both of which turned out to be successful. Ammonium chloride helped maintain temperatures between 2 to 6°C, ideal for most vaccines, while barium hydroxide octahydrate could achieve subzero temperatures, useful for certain vaccines and transplant organs.
The Thermavaultconsists of an insulated plastic body with an inner copper chamber where the medical contents are stored. The salt solution is poured between the plastic and copper walls. Unlike traditional ice-based cooling systems, the salt solution is reusable and can be regenerated by boiling off the water and reusing the recovered salt.
Global Recognition and Next Steps for the Thermavault Revolution
The innovation earned them the 2025 Earth Prize, along with $12,500 in funding, which they plan to use to manufacture 200 units and test them in 120 hospitals. Dr. Pritesh Vyas from V One Hospital in Indore confirmed the device could maintain vaccine temperature for 10 to 12 hours and suggested improvements like a built-in temperature monitor.
The team aims to secure WHO’s Performance, Quality and Safety certification and pitch the fridge to Gavi, a global vaccine distributor. The Earth Prize also provides support for patenting their design. As regional winners representing Asia, the team is now in the running for the global Earth Prize title, which will be decided by public vote.
Summary:
Three teens from Indore invented Thermavault, a salt-powered fridge to transport vaccines without electricity. Using ammonium chloride and barium hydroxide, it maintains cold temperatures and is reusable. Their innovation won the 2025 Earth Prize and $12,500, which they’ll use to test 200 units in hospitals and pursue global certification.
