Prediction of space heating and formaldehyde degradation behaviors for the sorption heat storage-photocatalysis combined solar envelope

This article introduces a solar building envelope that integrates salt hydrate-based sorption thermochemical energy storage and photocatalysis to provide a dual functionality of space heating and formaldehyde degradation. The system's heat output and air purification effectiveness under dynamic exterior conditions are numerically investigated based on the developed multi-physics coupling model. Numerical results reveal that during the charging phase, both the outlet air temperature and the formaldehyde degradation rate initially rise and then decline, peaking at a temperature of 45.1 °C at about 14:30. The clean air delivery rate and degradation rate achieved are 25.5 m³/h, and 7.3425 μg/s, with a total energy efficiency of 72.9 %. The discharging phase commences at 19:40, elevating the outlet air temperature from 30 °C to approximately 38.4 °C, and the discharging period extends for over 10 h. The average temperature lift of air and heating power of the storage wall are 17 °C and 19.1 kW/m³, respectively. Moreover, the influence of various factors such as solar radiation intensity and relative humidity on the system's performance are systematically investigated. The findings of this study may contribute valuable insights into the advancement of efficient solar building envelopes.