Experimental investigation of indoor lighting/thermal environment of liquid-filled energy-saving windows

To enhance the effectiveness of energy-saving buildings, windows play a crucial role, as they contribute to comfort, energy efficiency, and adaptability. However, traditional static windows, which primarily focus on reducing solar radiation, struggle to strike a balance between heating/cooling requirements during winter and summer seasons. On the other hand, dynamic windows, while offering adjustability, suffer from issues such as high haze and poor color rendering, making them less suitable for residential buildings. In this study, we propose a novel reversible liquid-filled energy-saving window that effectively regulates indoor solar radiation heat gain. To evaluate the dynamic indoor light/heat environment provided by liquid-filled energy-saving windows, we conduct an experimental investigation. Results indicate that windows filled with 10 wt% and 20 wt% CuSO4 solution cause a 1.5 °C and 2.5 °C reduction in indoor mean air temperature compared to water-filled windows during the summer season. Similarly, in the winter season, the decrease is 1.4 °C and 0.5 °C, respectively. Moreover, there is no significant difference in indoor illuminance between energy-saving windows filled with 10 wt% and 20 wt% CuSO4 solution. With the mass concentration of 10%wt CuSO4 solution, indoor mean illuminance difference between the two groups is only 236 lux and 214 lux during the summer and winter seasons, respectively.