Experimental investigation of indoor lighting/thermal characteristics of highly sensitive mechano-chromic energy-saving windows

Windows play a crucial role in reducing energy consumption in buildings. In the case of conventional static windows, it is difficult to strike a balance between heating and cooling in winter and summer. Dynamic windows are adjustable but have a complex structure, with high cost and low sensitivity, limiting their suitability in residential buildings. In this study, we propose a novel mechano-chromic energy-saving window that effectively regulates indoor solar radiation heat gain. The proposed structure outperforms existing mechano-chromic windows, achieving significant transmittance modulation with small associated strains, attaining a solar light transmittance modulation of 24.09 % with a strain of 5 %. In a series of experimental tests, the force-induced chromogenic energy-saving window lowered the average indoor air temperature in summer mode by 1.61 °C and 4.46 °C compared with standard double-pane insulating windows when subjected to strains of 5 % and 10 %, respectively. In winter mode, the associated decrease in temperature is 0.37 °C. Tests in summer have established differences in average indoor illuminance of 102 lux and 155 lux for a strain of 5 % and 10 %, respectively. The difference in indoor illuminance for the experimental (mechano-chromic) and control (double pane insulation) groups in winter mode is negligible.