Teens invent electricity-free refrigerators that run on a common household item

Sometimes teenagers come up with the best ideas. Three teens from Indore, India have found a way to help their parents who work in the medical field. Using their brains and ingenuity, they have developed a mini-fridge that can keep vaccines and other medicines cold and preserved without the need of an electrical outlet or battery. Their secret? Salt.

Their “Thermavault,” as they call their invention, was so innovative and successful that they won $12,500 from the 2025 Earth Prize. While many teens would understandably spend the prize money on themselves, Dhruv Chaudhary, Mithran Ladhania, and Mridul Jain have decided to spend the money on creating 200 more Thermavaults and distribute them among 120 hospitals for further testing. The hope is that this new invention will help hospitals in rural areas keep vaccines and even organs preserved for transport.

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"We have been able to keep the vaccines inside the Thermavault for almost 10 to 12 hours," said Dr. Pritesh Vyas, an orthopedic surgeon at V One hospital in a testimonial. “It will be definitely helpful, definitely useful in the remote places, the villages."

How does this whole thing work? Well, some salts are able to achieve a cooling effect by pulling heat from their environments as they’re dissolved in water. This is because when the salts dissolve, they require energy to break apart the charged ions—so they pull it from the environment. This ends up cooling the water around them. The fridge itself is an insulated plastic container with a copper wall lining the inside, where the vaccines, medicines, or organs would sit. Meanwhile, the cooling solution made of the salt dissolving in water is poured into a space between the plastic outer wall and the copper inner wall. The teens were able to create a container that could harness this scientific process to keep items within that environment cool.

While the boys were going to test 20 different types of salt compiled from a list of 150 salts they researched online, they ended up using two different salts recommended by their teacher: barium hydroxide octahydrate and ammonium chloride. While ice packs and coolant boxes are already being used in the field to transport organs and other medical items, the advantage of the Thermavault’s ammonium chloride solution is that you don’t need a freezer to pull ice from. Instead, the solution in the Thermavault can be boiled, the salt can be collected, and then be dissolved again to produce its cooling effect.

This trio isn't the only group of teens to make revolutionary inventions. Chester Greenwood would invent ear muffs while ice skating as a 15-year-old in 1873. Mathematician Blaise Pascal invented what we would consider the modern mechanical calculator before he turned 18. Even braille was invented by 15-year-old Louis Braille.

This goes to show that young people can come up with some highly intelligent inventions and ideas that can benefit everyone—that is if adults take the time, effort, and energy to listen and invest in their ideas.