Mumbai, Jun 23 (PTI) Researchers at the Indian Institute of Technology Bombay (IIT Bombay) have developed a prototype that can capture the intense summer Sun and save it to sustainably warm homes during winter in the Himalayan north where temperatures drop well below freezing point.
The prototype was developed using strontium bromide, a salt compound that stores solar heat and releases it in the winter -- offering a clean, smoke-free alternative to diesel heaters and firewood that many Himalayan communities still rely on, the IIT Bombay said on Monday.
A module capable of storing about 500 kilowatt-hours of energy was designed to help the communities have access to sustainable heating options in winters, said Dr Rudrodip Majumdar, who worked on this project as a postdoctoral fellow at the IIT Bombay.
The whole setup consists of a simple, modular unit designed to be easy to transport and operate. It includes solar thermal collectors that heat air during summer, a reactor chamber filled with strontium bromide salt, and a small air circulation system to trigger dehydration and rehydration cycles, said the institute.
The reactor components are housed in a compact, weatherproof unit designed for Himalayan conditions and are insulated using glass wool, it said.
"Solar collectors are well-proven. Steel tanks have been made for ages. The only new contribution is stabilising the thermochemical material and packaging it for daily life. This kind of long-term seasonal storage is made possible because the energy stored in the material is very stable. It does not degrade over time," noted Majumdar, who now works with the Bengaluru-based National Institute of Advanced Studies (NIAS).
According to IIT Bombay researcher Dr Sandip Kumar Saha, who led the study, each storage module is roughly the size of two LPG cylinders and designed to be portable.
They can be recharged in the summer at solar stations - possibly even in sunnier regions like Gujarat or Rajasthan - and trucked up to Himalayan towns just before the start of winter, he maintained.
"Once you deploy this material, you don't need to change it. If you maintain the reactor with basic precautions, the operation and maintenance costs come down. These are very sturdy reactors," Majumdar added.
The researchers have already tested the material through six full charging and discharging cycles in the lab, with no performance degradation. Thermochemical salts like strontium bromide are theoretically capable of 500 to 600 cycles, which means that each unit could last years.
While the upfront investment may be higher than diesel heaters, the study found thermochemical systems are more economical over time, especially in remote regions where prices of the fuel are inflated due to transportation costs and where the environmental impact, or potential penalty from carbon emissions, adds to the overall burden.
"If we want to produce electricity from diesel currently, it will cost us Rs 50 per unit (kWh). If we add a carbon penalty, it could go up to Rs 78 per unit. Then the thermochemical solution will be half the price between Rs 33-51 per kWh in different Himalayan cities," explained Majumdar.
Another researcher associated with the study said they are in the process of developing thermal storage solutions for round-the-year, smoke-free heating of camps of Indian Army personnel posted in high altitude areas.
"Solar thermal energy solutions for space-heating have been successfully tested in harsh climatic conditions for the Indian Army at sub-zero temperatures. We are in the process of developing thermal storage solutions for round-the-year, smoke-free heating of camps of Army (personnel) stationed at such high altitudes," said Dr Chandramouli Subramaniam from IIT Bombay, who worked on the study.