IIT Bombay Powers Up Winter with Solar Thermal Tech

In a significant breakthrough for winter heating in India’s cold desert regions, researchers at the Indian Institute of Technology Bombay (IIT Bombay) have developed a solar-powered thermal battery that stores summer heat for use during the harsh Himalayan winters.

The technology promises a sustainable alternative to diesel heaters widely used in regions like Leh, where sub-zero temperatures persist for months.

A Cleaner Heat Source Using Strontium Bromide

The system relies on a thermochemical storage solution using strontium bromide. It is an energy-dense, stable, non-toxic, and environmentally safe material.

Developed by researchers Ankush Shankar Pujari, Rudrodip Majumdar, Chandramouli Subramaniam, and Sandip Saha, the battery module can store up to 500 kilowatt-hours of heat, enough to warm a small Himalayan home for four months.

Diesel heaters are not only carbon-intensive but also have costly fuel compared to free solar heat. The new module offers a more sustainable and long-term option, reducing dependence on polluting fuels.

How the System Works

The setup comprises solar thermal collectors that absorb heat in summer and transfer it to a reactor chamber filled with strontium bromide salt. Through dehydration and rehydration cycles, the salt stores and later release heat when air is passed through the chamber. The unit is compact, weatherproof, and well-insulated for high-altitude climates.

Rudrodip Majumdar, now at the National Institute of Advanced Studies, highlighted the system’s seasonal energy storage capability. It is ideal for regions with long, frigid winters and limited energy access.

Moreover, the lab tests have confirmed six full charge-discharge cycles without performance loss. Notably, the salt can withstand up to 600 cycles, ensuring years of reliable use.

Portable and Cost-Effective

According to the study lead, Sandip Saha, the module is roughly the size of two LPG cylinders and is designed to be portable. It could be charged in sunny regions like Gujarat or Rajasthan and transported to the Himalayan towns before winter.

Furthermore, while the initial cost of the solar thermal battery is higher than a diesel system, it offers better economics over time, especially in remote regions where diesel prices are inflated.

The study calculated the system’s Levelized Cost of Heating (LCOH), a measure of average lifetime heating cost, at INR 33 to INR 51 per kWh in various Himalayan cities. In Leh, LCOH was lowest at INR 31/kWh, making it more affordable than diesel heating when factoring in fuel transport and environmental impact.

Looking Ahead

Globally, thermochemical storage remains in the pilot stage, with trials in countries like Germany. In India, while lab success is promising, full-scale deployment in homes may take some time. However, the technology promises a practical and scalable solution for clean winter heating in remote and high-altitude regions, and a step toward decarbonising India’s diverse heating needs.