Three teenagers from Indore — Dhruv Chaudhary, Mithran Ladhania, and Mridul Jain — have won the prestigious Earth Prize 2025 and a $12,500 award for inventing a salt-powered refrigerator that requires no electricity. Their creation, aimed at improving vaccine and medical supply storage in rural areas, is called Thermavault.
Inspired by the challenges of delivering COVID-19 vaccines to remote villages, the trio set out to develop a refrigeration system that could operate without power. Their solution uses salts that absorb heat from their surroundings when dissolved in water, providing a cooling effect.
How Thermavault Works
Thermavault is an insulated plastic container lined with copper on the inside. Vaccines, medicines, or transplant organs are stored inside, while the cooling solution — a mix of water and salts — circulates between the plastic exterior and copper interior walls.
The technology relies on certain salts’ ability to absorb environmental heat during dissolution. After extensive research, the students tested around 20 different salts at an Indian Institutes of Technology (IIT) laboratory. Though initial attempts failed, they eventually returned to a ninth-grade science principle, discovering that ammonium chloride could maintain temperatures between 2–6°C (35–43°F) — ideal for most vaccines. By adding barium hydroxide octahydrate, they achieved sub-zero temperatures suitable for preserving transplant organs.
According to Dr. Pritesh Vyas, an orthopedic surgeon at V One Hospital in Indore who tested the device, vaccines stored inside the Thermavault remained viable for 10 to 12 hours. He noted that with enhancements like a built-in temperature monitor, the device could be a game-changer for rural healthcare.
Unlike conventional cold boxes that rely on ice packs and freezers, Thermavault’s salt solution is reusable and operates entirely without electricity — a significant advantage in remote regions.
What’s Next
With their Earth Prize winnings, Chaudhary, Ladhania, and Jain plan to produce 200 Thermavault units for testing across 120 hospitals. Their invention not only holds promise for vaccine storage but could also revolutionize the transport of critical medical supplies and organs.
The Earth Prize, organized by The Earth Foundation, is an annual global competition recognizing outstanding environmental innovations by secondary school students. Chaudhary, Ladhania, and Jain have been named the winners for the Asia region. A global winner will be announced soon.
