Teen‑invented, salt‑powered fridge cuts hospitals\’ power bills, 200 on order

A Trio of Teens Pioneer Salt‑Powered Mini‑Fridge for Rural Medical Transport

Three young engineers from Indore, India—Dhruv Chaudhary, Mithran Ladhania, and Mridul Jain—have crafted a compact refrigerator that relies solely on a salty cooling method and requires no electrical outlet. The device, named Thermavault, is aimed at making it easier to deliver vaccines, medicines, and even transplant organs to hospitals in remote villages that lack electricity.

Background and Inspiration

• All three boys grow up in a household with parents who work in the medical field.
• They became aware of the difficulty of transporting COVID‑19 vaccines to rural areas without a power source.
• Motivated by this challenge, they set out to design a refrigeration technique that uses salt as the cooling agent.

Acknowledgment and Prizes

• Their invention qualified for the 2025 Earth Prize, and they emerged victorious on Saturday.
• The award carries a prize of $12,500, which they plan to allocate toward building 200 Thermavault units.
• They also intend to distribute these units to 120 hospitals for practical testing.

Testing and Practical Usage

• Dr. Pritesh Vyas, an orthopedic surgeon at V One Hospital in Indore, documented a video test of the Thermavault.
• During the trial, the device successfully maintained the temperature inside the fridge for approximately 10 to 12 hours.
• Dr. Vyas suggested that incorporating a built‑in temperature monitor would enhance the device’s practicality, particularly for remote villages.

Future Plans and Impact

• The trio hopes that Thermavault will assist in transporting vaccines, other medicines, and supplies, and even transplant organs to hospitals lacking electricity.
• By building 200 refrigerators and deploying them to 120 hospitals, they aim to create a reliable, out‑of‑the‑box solution for medical transport in rural India and beyond.

Finding the right cooling salt

barium hydroxide octahydrate and ammonium chloride: The two salts that changed the cooling experiment

When salts dissolve in water, the ions that make up the salt separate.
That separation consumes energy; the ions therefore take heat from the surrounding water, producing a cooling effect.

Initial search and extensive list

• 150 salts were identified online as candidates for the cooling effect.
• After evaluating their properties, the list was shortened to about 20 salts that seemed most promising.

Laboratory testing at IIT

• Researchers used a laboratory at an Indian Institute of Technology to test the 20 selected salts.
• Despite careful measurement, none of the salts produced a noticeable cooling effect on the water.

Teacher’s recommendation and breakthrough

• After the disappointing results, a teacher suggested testing two different salts.
• The salts were barium hydroxide octahydrate and ammonium chloride.
• These two salts displayed a pronounced cooling effect, confirming the theoretical explanation of ion separation and energy absorption.

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Three scientists reveal a surprisingly simple cooling solution

Chaudhary explained that their quest for the most efficient salt took them back to a high‑school science textbook.

• Ammonium chloride kept temperatures between 2 – 6 °C (35 – 43 °F), perfect for most vaccines.
• Adding barium hydroxide octahydrate dropped the mix below 0 °C, suitable for certain other vaccines and even for transplant organs.

Two refrigeration options were ready two months later

Within roughly three months, they had built a prototype and began field testing it in local hospitals.

Meet the Thermavault salt refrigerator

Reinventing Cold Chain with a New Thermavault

What the Prototype Looks Like

• Glass‑free insulated plastic housing lining the exterior
• Inner copper wall creates a low‑friction corridor
• Placed inside is a concentrated salt water bath

The influx of ammonium chloride solution between the plastic outer shell and the copper inner wall produces a steady cooling effect. When the solution cools, the salt crystals form and can be reused by simply boiling away the water and re‑dissolving the solid salt.

Why the Thermavault Stands Out

• It eliminates the need for a freezer or electric power
• Saltwater can be collected and re‑dissolved without any electricity
• It offers a reusable reagent for long‑term field operations

Future Plans and Certification

Following the award, the teens plan to pursue a Performance, Quality and Safety certification through the World Health Organization. This certification would open doors to pitch the prototype to Gavi, an international alliance that streams vaccines worldwide.

The Supporting Ecosystem

• The Earth Prize program provides a dedicated volunteer to assist in patent filing.
• Teen innovators from around the world compete globally, awarding one local winner in each region.
• The trio claimed the Asian award; the global winner will be decided by public vote, final vote closed on April 22.