Researchers at Texas A&M University have established foundational design principles for composite phase change materials that can rapidly store thermal energy. The breakthrough should dramatically simplify the design process, allowing a near-optimal composite phase change material to be simply calculated without exhaustive computational fluid dynamic calculations or extensive iterative design.
Several previous studies have investigated the performance of thermal-energy storage systems, but the present study is the first to provide insights into improving rate performance, optimisation and prediction of performance.
Phase change materials store thermal energy as latent heat. They are often integrated with high-thermal-conductivity metals to make composites that offer both a high power density and a large capacity for energy storage. The fundamental question addressed by the Texas A&M research was how to design a composite phase change material that balances both energy density (how much energy can be stored – the equivalent of how far an electric vehicle could travel before running out of charge) and power density (how quickly energy can be stored – the equivalent of how long it would take to charge up an electric vehicle) without adding excess mass or volume.
The research provides a theoretical framework for the design and optimisation of cylindrical composites with three figures of merit: minimisation of temperature rise, maximisation of the effective volumetric heat capacity and maximisation of the effective heat capacity based on mass. The figures of merit developed in this work can assess the performance of most composite phase change material systems and help design future cylindrical composites while accounting for the thermal loads specific to the thermal storage application.
Importantly, the team experimentally demonstrated that treating the system as an effective composite allowed them to quickly simplify the calculations and predict near-optimal structures.
The research has been published in the International Journal of Heat and Mass Transfer.