Bae Minyeol, Kim Do Hyeon, Kim Sun-Kyung, Song Young Min
School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology (GIST), Cheomdangwagi-ro 123, Buk-gu, Gwangju 61005, Republic of Korea.
Department of Applied Physics, Kyung Hee University, Gyeonggi-do 17104, Yongin, Republic of Korea.
Nanophotonics. 2024 Jan 9;13(5):749-761. doi: 10.1515/nanoph-2023-0580. eCollection 2024 Mar.
Passive radiative cooling has emerged as a sustainable energy-saving solution, characterized by its energy-free operation and absence of carbon emissions. Conventional radiative coolers are designed with a skyward orientation, allowing for efficient heat dissipation to the cold heat sink. However, this design feature presents challenges when installed on vertical surfaces, as nearby objects obstruct heat release by blocking the cooler's skyward view. Here, we introduce a directional radiative cooling glass (DRCG) designed to facilitate efficient heat dissipation through angular selective emission. The DRCG is constructed as a multilayer structure incorporating epsilon-near-zero materials, specifically SiN and AlO, layered on an indium-tin-oxide thermal reflector. This innovative design restricts thermal emission to specific angular ranges, known as the Berreman mode. Additionally, the transparent layers enable a visible transmittance exceeding 84 %. Theoretical simulations validate the enhanced cooling performance of the DRCG, exhibiting a temperature reduction of over 1.5 °C compared with conventional glass in hot urban environments characterized by a nearby object temperature exceeding 60 °C and a sky view factor of 0.25. Furthermore, outdoor experiments demonstrate that employing the DRCG as a window enhances space-cooling performance by ∼1.5 °C. These findings underscore the potential of transparent energy-saving windows in mitigating the urban heat island effect.
被动辐射冷却已成为一种可持续的节能解决方案，其特点是无需能源且无碳排放。传统的辐射冷却器设计为朝上放置，以便有效地将热量散发到冷的散热器。然而，当安装在垂直表面上时，这种设计特点会带来挑战，因为附近的物体通过阻挡冷却器向上的视野来阻碍热量释放。在此，我们介绍一种定向辐射冷却玻璃（DRCG），其设计目的是通过角度选择性发射来促进高效散热。DRCG构建为一种多层结构，包含近零介电常数材料，特别是SiN和AlO，层叠在氧化铟锡热反射器上。这种创新设计将热发射限制在特定的角度范围内，即所谓的贝里曼模式。此外，透明层的可见光透过率超过84%。理论模拟验证了DRCG增强的冷却性能，在附近物体温度超过60°C且天空视角因子为0.25的炎热城市环境中，与传统玻璃相比，温度降低超过1.5°C。此外，户外实验表明，将DRCG用作窗户可使空间冷却性能提高约1.5°C。这些发现强调了透明节能窗户在缓解城市热岛效应方面的潜力。
