A systematic assessment on a solar collector integrated packed-bed single/multi-layered latent heat thermal energy storage system

Abstract

Thermal energy storage (TES) methods stand out as a key technology that eliminates the supply-demand imbalance in cooling or heating systems. This paper focuses on investigating the charging performance of the solar-aided packed-bed latent heat TES system. An in-house 1D transient mathematical model is developed to simulate the latent heat TES system's heat transfer phenomena. The TES tank is integrated with a flat plate solar collector to include the variable boundary condition effects of solar energy and ambient air. The enhanced thermal conductivity approach is implemented into the mathematical model to consider the natural convection effects of the PCM's liquid phase, and the method is validated. The mathematical model of the packed bed latent heat TES tank is also validated with the experimental and numerical results from the literature. As design and working parameters, the mass flow rate of heat transfer fluid (HTF) and spherical storage material diameter are varied. Single-, double- and triple-phase change material (PCM) arrangements are also studied by varying the melting temperature of PCM along the flow direction. The time-wise variation of energetic and exergetic efficiencies of the integrated system, PCM mean temperature inside the storage tank, and the liquid fraction in flow direction are investigated. Further extensive parametric analyses are conducted for heating season months, i.e., November, December, January, and February. As a result, the best design and working conditions for the integrated latent heat TES system within the range investigated are proposed. Also, it is concluded that decreasing the capsule diameter and increasing the HTF's mass flow rate has a positive effect on system indicators.