Pune: Researchers at MIT World Peace University (MIT-WPU) have developed an innovative solar thermal battery that enables hot water availability even after sunset by storing solar heat in a phase change material (PCM)-based thermal storage system.
The breakthrough addresses one of the major limitations of solar energy—its intermittent availability—and has the potential to significantly reduce dependence on electricity and fossil fuels for water heating applications.
The solar thermal battery has been developed by Dr. Anita Nene and Dr. Rohit Ghadge from the Department of Mechanical Engineering at MIT-WPU.
The system integrates a Scheffler solar concentrator with a thermal storage capsule containing paraffin wax, a phase change material capable of storing and releasing substantial amounts of heat.
Unlike conventional energy storage systems that depend on electrochemical batteries, this solar thermal battery stores energy directly in the form of heat.
The system incorporates a detachable PCM tube, a water-jacket heat transfer mechanism, and polyurethane insulation to maximise heat retention and improve overall energy utilisation.
According to the researchers, laboratory-scale testing demonstrated complete thermal charging in approximately 18 minutes and complete discharge in nearly 32 minutes.
The solar thermal battery continued supplying hot water even after solar input was removed, highlighting its ability to provide thermal energy beyond daylight hours.
The prototype stores approximately 1.5 to 2 kWh of thermal energy and can maintain water temperatures between 50°C and 60°C for up to 12 to 14 hours after charging.
The innovation offers a sustainable alternative to conventional electric water heating systems while improving energy efficiency.
“One of the major limitations of solar energy is that it is available only when the sun is shining. Our objective was to develop a simple, cost-effective, and sustainable thermal storage solution that can store solar energy and make it available whenever required,” said Dr. Anita Nene.
“Thermal energy accounts for a substantial share of overall energy consumption. Technologies that enable efficient storage of solar heat can help reduce dependence on conventional fuels, improve energy security, and support the transition towards cleaner and more sustainable energy systems,” said Dr. Rohit Ghadge.
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To evaluate the performance of the solar thermal battery, the researchers conducted Computational Fluid Dynamics (CFD) simulations alongside laboratory-scale validation studies.
The technology has currently achieved Technology Readiness Level (TRL) 7 and is being prepared for pilot deployments in real-world settings.
Potential applications of the solar thermal battery include residential water heating systems, hotels, hospitals, hostels, educational institutions, industrial process heating facilities, community kitchens, agricultural operations, and off-grid rural communities.
The research team has filed an Indian patent application titled “Solar Energy Storage Capsule Using Phase Change Material” under Application No. 202521118546.
The researchers are now exploring collaborations with industry partners to facilitate pilot deployment and commercialisation of the technology.
“The next phase of development will focus on field trials, performance optimization, and scale-up for commercial deployment,” said Dr. Anita Nene.
Researchers estimate that widespread deployment of the solar thermal battery could lower carbon emissions by approximately 2.5 to 3 tonnes annually, thereby contributing to India’s clean energy and sustainability goals.
