Design optimization of the cooling systems with PCM-to-air heat exchanger for the energy saving of the residential buildings

Driven by a rapid surge in cooling demand in buildings, the energy consumption dedicated to cooling has experienced remarkable growth. To address this challenge, the adoption of latent heat thermal energy storage utilizing phase change materials (PCM) has gained significant momentum in recent years. This paper presents the design and evaluation of an integrated latent heat thermal energy storage (ILHTES) system tailored for residential buildings. This system integrates a PCM-to-air heat exchanger (PAHX) with an air conditioning unit. Modelica language is utilized to develop a numerical model for the ILHTES system. The heat transfer model of the PAHX is developed and validated using existing literature data. To simulate the dynamic behavior and energy consumption of the residential building, the open -source library AixLib is adopted. The developed ILHTES system model is used for the optimization of key design variables, including the PCM slab thickness and air flow rate, based on the results of long-term simulations covering the entire cooling season. Evaluation of the energy saving potential of the optimized ILHTES systems is carried out in comparison to conventional air conditioning systems, considering various climatic conditions in five European cities. The results highlight the profound impact of PCM types on the Energy Saving Ratio (ESR) throughout the entire cooling season. Among the four commercially available PCMs examined - RT27, RT25, RT20, and RT18 - RT25 consistently outperforms the others. Across all five cities investigated, using RT25 leads to a minimum ESR of 16% in Catania and a maximum ESR of 44.7% in Stockholm for the entire cooling season.