IIT-Bombay's new solar heaters may aid Indian troops guarding northern borders

New Delhi, Oct 24: In what may aid troops guarding the northern borders, scientists at IIT-Bombay have come out with a new type of nanomaterial to make solar heaters for keeping the tents or hutments used by the troops warm without polluting the environment and putting the occupants at risk.

The heaters are under trial by the Indian Army even as the researchers are in the process of incubating a company that will manufacture them on a commercial scale.

Currently troops in Ladakh or other high altitude areas rely on Kerosene-based heaters to keep their habitats warm to brave the harsh climate. The IIT technology gives a viable and non-polluting alternative as the marigold-looking material offers an unprecedented solar-thermal conversion, turning most of the light that hits it into heat.

Known as nano-structured hard carbon florets or NCF, the material has shown an unprecedented solar-thermal conversion efficiency of over 87 per cent.

It absorbs more than 97 per cent of the ultraviolet, visible and infrared components of sunlight and converts them efficiently into thermal energy. The heat thus produced can be effectively transferred to either air or water for practical applications.

The NCFs can heat the air from room temperature to 60 degrees Celsius and provide smoke-free space-heating solutions. “This is particularly relevant for heating spaces located in cold climatic conditions that receive abundant sunshine such as Leh and Ladakh, which gets over 300 days of clear sky and sunshine in a year,” said C Subramaniam from IIT-Bombay, the lead author of this study.

The IIT team, with support from the Indian Army, is carrying out trials for the NCF-based space-heaters, but is reluctant to share details. “Burning oil inside a tent in high-altitude areas is dangerous because it reduces the oxygen level and exposes the occupant to poisonous carbon monoxide. This offers a better alternative,” he said.

Solar thermal converters, like those present in solar water heaters, are in use in many places around the world. However, commonly available solar heat absorbers are often expensive, bulky and potentially harmful to the environment. Their conversion efficiency is also less when compared against NCF.

"The best commercial ones in the market operate at 70 per cent solar-thermal conversion efficiencies,” said Ananya Sah, the lead author of the study. The NCFs on the other hand are made primarily of carbon, inexpensive to produce, environment-friendly and easy to use and have an efficiency of more than 87 per cent.

The structure of the nanoparticles of NCF resembles marigolds in appearance, composed of interconnected tiny cones of carbon. The NCF’s uniqueness stems from the structure that allows blooming of such unusual properties.

Once manufactured, the NCFs can be spray-painted onto almost any surface, similar to powder coating a surface, reducing the cost of application and maintenance as well. “We have shown that the coating is possible over surfaces such as paper, elastomer, metal and terracotta clay,” said Subramaniam.

The company being formed by the IIT team will manufacture the paint and the space-heater. There is also a third application involving an efficient way to evaporate water as the NCF has the ability to convert water into vapour with an efficiency of 186 per cent, the highest ever recorded.

“The company will be functional in another six months when we will explore all the applications,” he added.