Three teenagers from Indore, Madhya Pradesh, have developed an electricity-free refrigerator that uses salt and water to keep vaccines and medicines cool, potentially helping transport temperature-sensitive medical supplies to remote villages.
Dhruv Chaudhary, Mithran Ladhania and Mridul Jain developed the device, named Thermavault, after learning about the challenges of storing and transporting Covid-19 vaccines in rural areas with unreliable electricity. Their invention won the 2025 Earth Prize for Asia, earning them $12,500.
The team plans to use the prize money to manufacture 200 units and distribute them to 120 hospitals for testing.
HOW DOES IT WORK?
Thermavault uses the cooling effect produced when certain salts dissolve in water. The process absorbs heat from the surroundings, lowering the temperature inside the refrigerator without electricity, batteries or ice.
The students initially researched around 150 salts before testing shortlisted compounds in laboratory facilities at the Indian Institutes of Technology (IIT). Their breakthrough came when their teacher suggested ammonium chloride and barium hydroxide octahydrate, both covered in their Class 9 science textbook.
Tests showed that ammonium chloride could maintain temperatures between 2 and 6 degrees Celsius, a range suitable for storing many vaccines. Adding barium hydroxide octahydrate could bring temperatures below zero.
The device consists of an insulated plastic container with a copper lining. Medical supplies are stored inside the copper-lined compartment, while the salt-and-water solution occupies the space between the inner and outer walls.
The cooling material can also be reused. The solution is heated to evaporate the water, leaving the salt behind, which can then be dissolved in fresh water for another cooling cycle.
According to a Business Insider report, a doctor who tested the device at V One Hospital in Indore found that it could keep vaccines cool for around 10 to 12 hours.
The students are now working towards obtaining Performance, Quality and Safety certification through the World Health Organization (WHO). They also plan to present the technology to Gavi, an international alliance working to improve access to vaccines.
Their invention demonstrates how a concept from a school science textbook can be developed into a practical solution to challenges in healthcare delivery.