Numerical analysis of cold thermal energy storage systems using macro-encapsulated Phase Change Materials (PCM) in residential cooling applications

The study focuses on the numerical simulation of the charging and discharging phases of a thermal energy storage designed for cold applications, utilizing water and a macro-encapsulated Phase Change Material (PCM). The experimental setup, used for the experimental validation, comprises an electric chiller, a heat exchanger, and a 320-liter cold storage tank containing 55 aluminum bottles filled partially with a biological PCM. This setup experimentally simulates a residential scenario in Italy's climate zone E, characterized by minimum winter temperatures below 0 °C and maximum summer temperatures over 25 °C. Numerical simulations are performed through the commercial solver COMSOL Multiphysics integrated with Matlab. A one-dimensional Matlab model simulates water behavior in the storage tank, while the performance of the PCM is analyzed using the Effective Heat Capacity (EHC) method in COMSOL Multiphysics. Key results include system charging/discharging times, water temperature variation, energy storage charge/discharge rates, and the PCM melt fraction. The numerical data on water temperature variations inside the tank are compared with experimental results, showing good agreement. Additionally, a parametric analysis is performed to assess how the size of the PCM container influences the system's performance.