Every winter, tens of thousands of Indian Army soldiers are stationed at altitudes where temperatures drop well below freezing, and the nearest fuel supply line is days away. With around 50,000 troops deployed at high altitude through the harshest months, keeping them warm has never been a single problem with a single fix — it’s been a stack of solutions, each solving part of the cold and leaving the rest.
The army had clothing that warmed the body but not the shelter, and stoves that warmed the shelter but still ran on fuel hauled in from days away. Photograph: (The Quint)
For years, the most reliable answer was kerosene, burnt inside cloth tents or iron container cabins. It worked, but it was expensive, polluting and, as innovator and educator Sonam Wangchuk would later discover, dangerous. His solar-heated tent is the newest entry in this line of solutions — but to understand why it matters, it helps to see everything the army was already doing to hold off the cold.
In 2021, he spoke to The Better India’s Rinchen Norbu Wangchuk about how he built it.
Warming the body
The first line of defence was never the shelter — it was the soldier. The force imported Extreme Cold Weather Clothing capable of keeping a body warm to minus 50 degrees, though it came at a cost of roughly Rs 800 crore a year and was often bulky. Battery-heated gloves and insoles tried to close the gaps electrically.
Every piece of this tent weighs under 30 kg, light enough for a soldier or porter to carry to posts no vehicle can reach. Photograph: (The Scroll)
But none of it warmed the tent that body slept in once the shift ended. Clothing kept a moving soldier alive; it did nothing for the sealed shelter waiting at the end of the day. That left the shelter to fuel — and fuel meant risk: burns, breathing trouble, and carbon monoxide with nowhere to go once a tent was sealed for the night.
A safer stove: DRDO’s Him Tapak
The traditional answer to a cold room in Ladakh and Kashmir has long been the Bukhari — a metal drum or cylindrical stove burning wood, coal or kerosene, venting smoke through a flue pipe in the roof. Simple to build and easy to fuel locally, it heated homes across the region for generations. But it was never designed for sealed, high-altitude military tents, where poor ventilation turned that same stove into a health hazard.
DRDO’s Defence Institute of Physiology and Allied Sciences set out to fix that, developing Him Tapak — an upgraded Bukhari built with safety in mind. It cut instances of soldiers dying from backblast and carbon monoxide poisoning, nearly halved oil use, and saved an estimated Rs 3,650 crore a year.
No heater. No wiring. Just sunlight, water and insulation working together to keep soldiers warm through the night. Photograph: (DNA India)
It was safer and cheaper than a plain kerosene stove — but it still needed fuel, carried up the same long routes as everything before it.
The gap that was left
So the army had clothing that warmed the body but not the shelter, and stoves that warmed the shelter but still ran on fuel hauled in from days away. Every fix so far depended, in the end, on that supply line.
This is the gap Sonam Wangchuk set out to close — not by replacing what already worked, but by adding an option none of the others could offer: warmth with no fuel at all. No kerosene, no oil, no batteries. Just a south-facing wall doing the work a supply line used to. He explained how he built it to The Better India’s Rinchen Norbu Wangchuk in 2021.
Letting the sun do the work
His answer was deceptively simple: let the sun do the work the fuel had been doing.
“The tent is very insulated from its surroundings with high degrees of solar intake,” Wangchuk said. A wall facing south lets sunlight stream in by day, and that heat doesn’t disappear once the sun sets. “We use the sun to collect the heat, water to store it, and the tent’s insulation properties help retain it for jawans at night,” he explained.
On the night Wangchuk first documented it, the tent held at +15 degrees Celsius at 10 pm while outside had fallen to minus 14 — a 29-degree gap achieved without a single flame or watt of electricity.
A decade of refinement
Wangchuk had already built a version of this idea once, for people whose lives depended on very different conditions. “This is the second prototype of a solar-heated tent I have made. The first one was made about a decade ago for nomads in the Changthang region,” he said. That earlier design never made it into wider use, but the idea stayed with him, waiting for a problem that would finally take it seriously.
It takes 40 individual pieces to build one tent, and no machinery to put them together. Photograph: (The Better India)
The army gave him that problem, with its own constraints: light enough to carry where no vehicle could reach, each piece under 30 kg. “To build a tent for 10 soldiers, it would require 40 such pieces,” Wangchuk said, describing a structure reassembled by hand — going up in two sections, a solar lounge gathering heat by day and a sleeping chamber holding that warmth at night.
At around Rs 5 lakh, it worked out to roughly half the price of the container cabins the army used. Built over a month at the Himalayan Institute of Alternatives with army input, it took the idea from Changthang’s nomad shelters to a military prototype.
Testing at Chang-La, and after
The tent was next headed for Chang-La pass, roughly 17,600 feet up — cold Wangchuk called “as tough as a location for testing purposes.” The then Defence Secretary called it timely and relevant, and HIAL still counts these tents among its ongoing work with the army years on.
The full details remain closely held by Wangchuk’s team, much like the ice stupas he built before it. If that pattern holds, this tent’s real impact may still be unfolding — powered by the one resource Ladakh has never run short of, and the one thing every fuel-based device before it never had: nearly 300 days of sunshine a year, for free.
A decade before this tent reached the army, a version of it was built for Ladakh’s nomadic herders. It never got adopted, until now. Photograph: (Ornate Solar)
Read the full feature to get the complete picture of his work.
