Adaptive building envelope combining variable transparency shape-stabilized PCM and reflective film: Parameter and energy performance optimization in different climate conditions

Abstract

Developing an adaptive building envelope (ABE) to cope with drastic changes in the ambient environment contributes to achieving the goal of net-zero emissions by 2050 in the building industry. In this study, two types of ABE, namely, adaptive ventilation and sunlight regulation wall (AVSRW) and adaptive sunlight regulation wall (ASRW), were designed by combining variable transparency shape-stabilized PCM (VTSS-PCM) and reflective film, and the AVSRW had an air cavity to control the heat storage and release of VTSS-PCM. The numerical models of the two ABEs and the massive wall (MW) were developed and validated by a full-scale experimental test. Based on these validated numerical models and weather datasets in four climate zones of China, the energy performances of AVSRW were simulated under the influence of melting temperature (Tm) of VTSS-PCM, thickness (L) of VTSS-PCM, and reflectivity (R) of reflective film. Then, a bi-objective global optimization was conducted to find the optimal performance and design parameters of AVSRW. Finally, the AVSRW and the ASRW with the optimal design parameters were compared with and the MW. The parameters analysis revealed that the combined action of Tm, L, and R on AVSRW determined the trade-off among the heat conducted to the interior, the solar energy stored by VTSS-PCM, and the solar energy reflected by the reflective film. The optimization results showed that, in the climate conditions of Beijing, Changsha, Guangzhou, and Harbin, the optimal values of Tm were 24.02 ℃, 24.37 ℃, 25.86 ℃, and 23.43 ℃, respectively; the optimal values of L were 0.16 m, 0.16 m, 0.09 m, and 0.16 m, respectively; the optimal values of R were 0.23, 0.29, 0.79, and 0.33, respectively. Under the optimal values of Tm, L, and R, compared with MW, the annual ESRs of AVSRW and ASRW were 84.26 % and 38.71 % in Beijing, 81.98 % and 39.45 % in Shanghai, 70.28 % and 55.53 % in Guangzhou, 76.20 % and 29.54 % in Harbin. This study provides the basis for the design and optimization of AVSRW and ASRW in different climate regions.