Three High School Students Create Refrigerator That Requires No Electricity – Win Global Sustainability Prize

April 21, 2025

Today's good news story comes from Madhya Pradesh, India.

In an inspiring leap toward sustainable innovation, three high school students—Dhruv Chaudhary, Mithran Ladhania, and Mridul Jain—have invented a revolutionary salt-powered refrigerator called the Thermavault.

The device requires no electricity and has the potential to transform life in communities without reliable access to power.

Dhruv, Mithran and Mridul / theearthprize.org

Their invention just earned them the prestigious 2025 Earth Prize and a $12,500 award, which the trio plans to use to build 200 units and distribute them to 120 hospitals for real-world testing.

The Thermavault is powered by a cooling method known as ionocaloric cooling, which uses the heat-absorbing reaction of salts dissolving in water. The primary cooling comes from ammonium chloride, a salt the students found could lower water temperature by up to 28°C. For deeper cooling—down to -10°C—they used a chemical reaction between barium hydroxide octahydrate and ammonium chloride, making the device suitable even for freezing applications with antifreeze.

A layer of fiberglass wool insulated with nitrile rubber surrounds a copper box inside the unit, helping it retain cool temperatures for long durations. Users simply pour the salt into the box, add water, and stir the solution using a gyroscope or by shaking. The result is even, efficient cooling—ideal for preserving food and medicine without electricity.

The team refined their process through extensive testing, working closely with Professor Mobin Shaikh, a material sciences expert at IIT Indore. They experimented with 15 different salts, applying principles like enthalpy and specific heat to optimize the design. Their rigorous research and hands-on prototyping paid off, impressing expert mentors and faculty who supported their innovation.

Beyond its scientific brilliance, the Thermavault holds promise for off-grid living, disaster relief, and rural healthcare—places where reliable electricity isn't a given. By offering an environmentally friendly way to preserve essentials, these young inventors are making a real impact.