A transient numerical simulation of a solar chimney system (SC), considering convective and radiative gains/losses to the exterior environment, in the warmest day of Madrid, Spain is presented. We performed a conjugate heat transfer analysis for SC with three types of absorbing materials:(1) SC with a lightweight plate (copper) - reference case, (2) SC with a phase change material (PCM 46-50) and (3) SC with a heavyweight wall (concrete). Numerical simulations for three orientations east (7:00-12 h), south (8:00-18 h), and west (12:30 to 18 h) were conducted to analyze the overall thermal performance of the SC throughout the day. The numerical in-house code was tested by solving two reference solutions reported in the literature, obtaining good agreement. Based on the numerical heat transfer analysis, the following is concluded: The SC with a copper plate shows the higher mass flow rates of 0.016, 0.019 and 0.016 kg/s for orientations east, west, and south, respectively. While the mass flow rate removed by the PCM configuration is higher than for the concrete wall configuration but is lower than for the copper plate (0.014, 0.017 and 0.0153 kg/s for orientations east, west, and south, respectively). The average thermal efficiencies of the SC with a copper plate are 34, 27 and 34% and with a PCM are 28,19.8, and 27% for orientations east, west, and south, respectively. The SC with a concrete wall shows the lowest thermal efficiency values. Finally, it was observed that for orientations east and south, the PCM layer does not change its phase and it remains in the mushy zone. It reaches its melting point on approximately 30-45 min for the three orientations. Conversely, the PCM changed its phase to a liquid state in 135 min for orientation west. (C) 2018 Elsevier Ltd. All rights reserved.