Analysis of heat charging and release processes in cascade phase change materials energy storage floor heating systems: Performance evaluation

Abstract

To address the issues of high energy consumption, significant temperature fluctuation and low heat release efficiency in conventional energy storage floor heating systems, this study proposes a novel solution known as the cascade energy storage floor heating system. This system incorporates two layers of phase change materials (PCMs) with distinct phase change temperatures as the thermal energy storage medium. A coupled heat transfer numerical model is developed to analyze the heat charging and release processes within the floor heating system. The evolutions of liquid fraction of PCMs, flow field and floor surface temperature are investigated during the heat charging and release processes. The findings demonstrate that the cascade PCM energy storage floor heating system avoids overheating and saves >19 % of energy consumption during the heat charging process, elevates the floor surface temperature by about 2 K during the late stage of heat release and thus reduces floor surface temperature fluctuation in comparison with the single-stage PCM system. These improvements are conducive to enhancing the energy utilization rate. Due to better synergistic solidification of the two PCM layers, the system with a PCM proportion of 1:1 exhibits superior overall heat release performance when compared to systems with PCM proportions of 1:2 or 2:1. The research outcomes provide a theoretical foundation and technical guidance for the practical implementation of cascade PCM energy storage technology in the field of building energy conservation.