Figure 1 - Optical Features and Schematic Diagram of the Ideal Windows for Hot and Cold Seasons
Figure 2 - Schematic Representation of the Rotatochromic Window
Figure 3 - Operating Principle of the Rotatochromic Window
Windows are often considered the weakest link in terms of building energy efficiency, accounting for approximately 40% of energy loss in buildings. To achieve carbon neutrality in buildings, it is crucial to focus on energy-saving innovations for windows. One effective approach to enhance window energy efficiency is by enabling dynamic solar spectrum regulation.
Solar radiation transmitted through windows consists of ultraviolet (UV), visible light (VIS), and near-infrared light (NIR). While VIS provides daylight, UV and NIR carry thermal energy that can heat up the indoor environment. During cold seasons, windows should be fully transparent across the entire solar spectrum to maximize solar heat gain in buildings. On the other hand, during hot seasons, windows should reject NIR and UV to reduce cooling energy consumption while maintaining high VIS transparency to optimize daylighting.
In our project, we propose a new concept of a rotatochromic window for solar regulation. This concept involves the synergistic development of two static optical materials and a reversible structure, allowing the window to switch between two distinct modes to adapt to the ideal features for both hot and cold seasons. The newly developed window can reduce the indoor surface temperature by approximately 11.2℃ and decrease building space cooling and heating energy consumption by 30% to 40%. It demonstrates excellent solar modulation ability (Tsol = 61%), high visible transmittance in both bleached (91%) and colored (56%) states, a high color rendering index (CRI > 80), and long-cyclic stability after 1000 cycles. With the advantages of facile fabrication and scalability, it is foreseen that the newly developed window holds promising prospects for next-generation low-carbon buildings.
Figure 1 - Optical Features and Schematic Diagram of the Ideal Windows for Hot and Cold Seasons
Figure 2 - Schematic Representation of the Rotatochromic Window
Figure 3 - Operating Principle of the Rotatochromic Window
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窗戶是建築節能的薄弱環節，窗戶冷熱損失造成建築約40%的能耗佔比。窗戶的光譜調控是實現窗戶節能的重要手段。太陽光譜是一多頻複光譜，包含紫外線、可見光以及近紅外線。建築全年期望引入可見光以提供自然照明，而對於紫外線和近紅外線的需求則因冬夏而異。
在我們小組的作品中，我們提出了一種新型可調控光譜的翻致變色窗。首先，我們提出一種翻致變色的窗框結構，並向窗體內部填充兩種光學性質截然相反且互不相溶的流體。由於兩種流體光學性質不同，配合窗體的特殊結構設計，可賦予窗戶兩種截然相反的光學特性，可適應冬夏不同需求。我們新開發的窗戶可將室內表面溫度降低11℃左右，同時降低約30%的建築能耗，有望為下一代低碳綠色建築提供技術支援。
圖1 - 理想窗戶在冷熱季節的光學特性與示意圖
圖2 - 翻致變色窗示意圖
圖3 - 翻致變色窗的操作原理
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