Team of Young researchers, still in Indian school, developed a portable, electricity-free refrigeration unit using a salt solution to keep vaccines and other temperature-sensitive materials cool. Team consisting of Dhruv Chaudhary, Mithran Ladhania, and Mridul Jain, is known for their work on Thermavault, a device designed to transport vaccines, medicines, and even transplant organs.
Thermavault uses ionocaloric cooling based on the dissolution enthalpy of ammonium chloride in water to fuel its cooling process. For its heavy duty cooling mechanism, it utilises the highly endothermic reaction between barium hydroxide octahydrate and ammonium chloride, wherein water is poured post-reaction. This creates a temperature gradient, and thus cools the contents inside.
Their results showed that ammonium chloride was the most effective salt. It could cool water by 28 degrees Celsius, down to 7 degrees Celsius, and it was also affordable via its reusability. They also found a reaction between barium hydroxide octahydrate and ammonium chloride that could cool water to -10 degrees Celsius with antifreeze. This would be ideal for freezing applications.
Electricity-free fridges are a game-changer for sustainable living, offering a practical solution for communities without reliable power. They can preserve food and medicine without electricity, reducing waste and promoting health. Perfect for off-grid living and disaster preparedness they combine energy independence with environmental responsibility.
They won The Earth Prize 2025 Asia for innovative first-of-its-kind electricity-free refrigeration unit for medical supply transport in remote areas, using reusable salt-based reaction.
They said after winning the Earth Prize 2025 Asia, "Our team was formed with a vision of sustainable design and a common love for Beyblades. The COVID pandemic served as a reminder of the lack of electricity availability in rural areas; we've seen, firsthand, the problems with transporting vaccines, food and essential supplies to these locations. Thus, we redesigned our science-fair cooling system into our solution. Thermavault uses salt-based endothermic reactions (which are reusable and sustainable) to create an electricity-free refrigeration unit. This solves many problems: plastic waste through thermocol, energy inequality, and inefficient cooling, especially for vaccines."
