Benefits of integrating phase-change material with solar chimney and earth-to-air heat exchanger system for passive ventilation and cooling in summer

Abstract

A solar chimney (SC) integrated with an earth–air heat exchanger (EAHE) produces a new passive system (SCEAHE) that can passively provide fresh air and cooling capacity. An inherent disadvantage of the coupled system is the mismatch of solar radiation, airflow, and internal load. To mitigate this issue and further improve the indoor thermal environment, a phase-change material (PCM)-based SCEAHE system is proposed and investigated using a validated numerical model. The thermal inertia of the SCEAHE system was improved by integrating PCM. The simulated results showed that the maximum absorber surface temperature of the SCEAHE system with PCM was 78.8 °C, 16.2% lower than without PCM. The PCM charging and discharging periods were approximately 9.5 h (05:30–15:00) and 14.5 h, respectively. The completely melted period lasted approximately 5 h (15:30–20:30); solidified PCM appeared from 02:00 to 7:15 with a maximum of 24% at 05:30. By integrating PCM, the SCEAHE airflow rate was increased by 50% at night, and the maximum airflow rate was reduced by 17.8% to 209.5 m3/h during the day. The EAHE outlet air temperatures varied between 24.8 and 26.5 °C, and between 24.4 and 27.2 °C for the SCEAHE with and without PCM, respectively. With the reduced outlet air temperature, the daily indoor air temperature for the SCEAHE with PCM varied between 25.1 and 28.4 °C; the maximum indoor air temperature was reduced by 0.8 °C compared with a SCEAHE without PCM, suggesting that including PCM in the SCEAHE system increases the useful cooling capacity and creates more stable indoor thermal comfort.