WHAT happens when a young Indian engineer moves from the sweltering heat of Andhra Pradesh to the Massachusetts Institute of Technology (MIT), in a state notorious for its -15°C winters? He feels very cold and has to wear multiple layers of clothing, which he then finds himself wanting to remove whenever he enters a warm classroom. Kranthi Vistakula, who found himself in just this situation, credits a dazed mind, as well as his professors at MIT, for his decision to invent an all-weather jacket designed to cope with extreme temperatures—from the heat of Mumbai to the chill of a Mount Everest base camp.

His first approach was to build a jacket with built-in heating and cooling systems. Packed with motorised fans, heating pipes and electric wiring, the resulting apparel was bulky and weighed 7 kilograms. “When I wore it to college, my friends joked that I was going to blow up the place," says Mr Vistakula. So he went back to the drawing board, and turned instead to a thermoelectric device called a Peltier plate, which operates like its better-known cousin, the thermocouple, but in reverse. A thermocouple consists of a junction between two different metals, which produces an electrical voltage related to the difference in temperature between them. Thermocouples are widely used as temperature sensors. A Peltier plate also consists of a junction between two metals, but forcing an electric current across the junction causes the metal on one side to heat up, and the metal on the other side to cool down. A Peltier plate can thus be used as a heat pump.

Mr Vistakula ended up incorporating multiple Peltier plates, built into lightweight plastic tiles, into a jacket. The tiles are powered by a rechargeable battery that is also incorporated into the garment. Depending on the direction of the current flow, the jacket can either pump heat from the interior to the exterior (providing a cooling effect in hot weather) or vice versa (warming the wearer). A proprietary coating on the outside of each Peltier cell helps accelerate the flow of heat. In 2007 Mr Vistakula returned to India to set up a company to refine his new invention, with support from a government incubator fund and the venture-capital arm of Reliance Group, an industrial giant. (Reliance has since sold its stake in the firm.)

The finished jacket weighs about 650 grams, can maintain internal temperatures of between 20 and 40°C and can operate in ambient temperatures between −50 and 50°C. It runs for about eight hours on a single charge. So far the Climaware jacket has been tested successfully by the Border Roads Association, part of the Indian Army. It tried out the jacket's heating function in environments including Khardungla, the world's highest road for motor vehicles, and the Siachin glacier, the world's highest battlefield, on the contested border with Pakistan. Other companies including Aspen Systems, Med-eng, Outlast and Foster-Miller offer similar products, in some cases using a chemical rather than an electrical approach to cooling and heating. Mr Vistakula says his technology, which he calls ClimaCon, is more easily recharged and results in lighter clothes.

ClimaCon is also being applied to other products by his company, Dhama Innovations, which is based in Hyderabad and employs 18 people. These include climate-controlled helmets, gloves, pain-relieving back and elbow wraps, car seats, shoes, and a cooling neck scarf for cricketers. “We can apply it anywhere,” says Mr Vistakula. One young engineer warmed a cup of coffee using a pair of ClimaCon shoes, which led to the idea of using the technology to make coasters and hot-plates. Climaware products for medical use went on sale in April, and an online store selling to consumers will open shortly. Will the market warm to Mr Vistakula's invention? He will soon find out.