Solid-solid PCM-based tree-shaped thermal energy storage system for solar cooling application

Abstract

This manuscript presents a comprehensive analysis of a solar cooling system, integrating a latent heat thermal energy storage (LHTES) with an absorption chiller, alongside a solar collectors’ field. The LHTES employs solid–solid phase change material (PCM), while the solar collectors belong to the parabolic type. Real-case boundary conditions are derived through the thorough examination of the overall system, encompassing user demands and operational dynamics. In particular, the study evaluates two distinct building scenarios, i.e., modern, and outdated buildings, considering both existing and new structures, to assess the flexibility and adaptability of the LHTES system to varying cooling demands. The preliminary system analysis gives a set of boundary conditions for the subsequent storage sizing and numerical simulations. Building upon these insights, the manuscript introduces a novel storage design inspired by tree-shaped configurations. This design – numerically simulated through a finite element code – aims to enhance heat spreading throughout the solid–solid PCM and maximize latent heat exploitation, thereby improving overall system efficiency and performance. The sizing of the storage system results in 487.8 kg, and 382.0 kg, for the modern and outdated building, respectively, and storage efficiency reaches a value of 86.15 % and 71.84 % for the charging phase and 97.70 % and 98.21 % for the discharging one, respectively. These results demonstrate the high instantaneous heat rate of the proposed LHTES, leading to high efficiencies in the charging and discharging phases.