Enhancing the efficiency of solar water heating systems in Iraqi homes: an experimental study and numerical modeling of the impact of phase change material (PCM) thermal energy storage units

Abstract

The substantial energy demand for domestic hot water in Iraq, coupled with the intermittent availability of solar energy, presents a significant challenge. Conventional solar water heaters (SWHs) often fail to provide a consistent hot water supply, particularly during post-sunset hours and overcast conditions. To address this limitation, this study investigates the integration of latent heat thermal storage, utilizing phase change materials (PCMs), into SWHs. A comprehensive methodology combining experimental analysis and numerical simulation was employed. An experimental prototype of a PCM-enhanced SWH was constructed and tested under the climatic conditions of Baghdad, and its performance was directly compared against a conventional SWH operating simultaneously. Concurrently, a dynamic heat transfer model was developed and validated in ANSYS Fluent to simulate the PCM's phase transition behavior and optimize system design.

The results demonstrate a significant performance improvement, the PCM-SWH extended the availability of hot water (>40°C) for an average of 4.3 hours after sunset, representing a 95% increase in operational duration compared to the conventional system. Furthermore, the daily thermal efficiency saw a relative increase of 23.5%, rising from 28.1% for the conventional SWH to 34.7% for the hybrid system, the study also identified optimal design parameters, including RT55 paraffin as the PCM, a mass of 30 kg, and a finned cylindrical storage unit configuration, this research confirms the technical viability and substantial benefits of integrating PCMs in solar water heaters for the Iraqi context, offering a practical pathway toward reducing dependency on the electrical grid and enhancing energy security.