Researchers at MIT World Peace University have developed a solar thermal energy storage system that enables hot water availability after sunset. The system stores solar heat in a phase change material-based thermal battery, helping reduce dependence on electricity and conventional fuels for water heating.

Developed by Dr Anita Nene and Dr Rohit Ghadge from MIT-WPU’s Department of Mechanical Engineering, the system combines a Scheffler solar concentrator with a thermal storage capsule containing paraffin wax. The phase change material stores and releases heat, allowing thermal energy to be used beyond daylight hours.

Unlike conventional electrochemical batteries, the system stores energy directly as heat. It includes a detachable PCM tube, a water-jacket heat transfer mechanism and polyurethane insulation to improve heat retention and energy utilisation.

During laboratory-scale testing, the technology achieved complete thermal charging in about 18 minutes and complete discharge in around 32 minutes. The prototype demonstrated 55 per cent thermal efficiency and continued supplying hot water after solar input was removed.

The system can store around 1.5 to 2 kWh of thermal energy and maintain water temperatures between 50 degrees Celsius and 60 degrees Celsius for up to 12 to 14 hours after charging. The researchers said the technology could help lower carbon emissions by around 2.5 to 3 tonnes annually.

The technology is currently at Technology Readiness Level 7 and is being prepared for pilot deployments in real-world environments. Potential applications include residential water heating, hotels, hospitals, hostels, educational institutions, industrial process heating, community kitchens, agricultural operations and off-grid rural communities.

An Indian patent application titled “Solar Energy Storage Capsule Using Phase Change Material” has been filed under Application No. 202521118546. The next phase will focus on field trials, performance optimisation and scale-up for commercial deployment."