Abstract
Solar chimneys represent a promising passive strategy to enhance natural ventilation and heating in buildings, contributing to reduced energy consumption and improved indoor thermal comfort. This study aims to evaluate the integration of various phase change materials (PCMs) into a solar chimney system for residential applications in Tehran, Iran, and to identify optimal configurations for energy-efficient operation. Four PCMs with distinct melting points—RT10, RT21, RT35, and RT42—were assessed for their ability to stabilize indoor temperature and reduce heating demands. A transient numerical model, developed in C++, simulated energy conservation and heat transfer processes using real meteorological data. The effective thermal capacity method was applied to capture phase change behavior, and the model was validated against experimental data with a maximum error of 9 %. Results revealed that PCM melting temperature significantly affects thermal performance and ventilation duration. RT35 provided nearly 24 h of continuous ventilation and achieved up to 75 % heating energy savings in October, outperforming concrete walls with 50 % savings. In colder months, RT21 was more effective, while RT42 showed limited performance due to incomplete melting. In November, RT42 reduced energy demand by 11 % compared to a single-mode solar chimney. Increasing PCM reservoir thickness to 40 mm improved performance, but further increases yielded diminishing returns. This research demonstrates the practical potential of integrating PCMs into solar chimneys for improved indoor climate control and energy efficiency, particularly in climates similar to Tehran, and offers insights for optimizing passive design strategies in building engineering.