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Tian Q, Tu X, Yang L, Liu H, Zhou Y, Xing Y, Chen Z, Fan S, Evans J, He S. Super-Large-Scale Hierarchically Porous Films Based on Self-Assembled Eye-Like Air Pores for High-Performance Daytime Radiative Cooling. Small 2022; 18:e2205091. [PMID: 36328709 DOI: 10.1002/smll.202205091] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 10/04/2022] [Indexed: 06/16/2023]
Abstract
Metal-free polymer daytime radiative cooling coatings with hierarchical eye-like air pores are proposed and fabricated with a super-large-scale film-stretching method. The hierarchically porous film (HPF) can be further coated with polymethyl methacrylate (PMMA) micro-hemispheres, forming coated HPF (cHPF), which do not dramatically change the optical or thermal properties. The cHPF is slightly better with a lower solar absorptivity (2.4%) and a higher thermal emissivity over the atmospheric transparency window (90.1%). The low solar absorptivity is due to the strong scattering of the hierarchical eye-like air pores, while the molecular vibrations and the focusing effect of the PMMA micro-hemispheres contribute to the high emissivity. An average mid-day temperature reduction of 7.92 °C is achieved relative to the air temperature, and the average cooling power reaches 116.0 W m-2 , which are much better than the cooling performances of the commercial cooling cushion. During the day, the cHPF-covered simulated building is up to 6.47 and 4.84 °C cooler than the ambient and the white painted counterpart, respectively. The film is durable and resistant to chemical etching, and very promising to use globally, especially in warm and tropical regions.
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Affiliation(s)
- Qing Tian
- Centre for Optical and Electromagnetic Research, National Engineering Research Center for Optical Instruments, College of Optical Science and Engineering, Zhejiang University, Hangzhou, 310058, China
| | - Xitao Tu
- Centre for Optical and Electromagnetic Research, National Engineering Research Center for Optical Instruments, College of Optical Science and Engineering, Zhejiang University, Hangzhou, 310058, China
| | - Liu Yang
- Centre for Optical and Electromagnetic Research, National Engineering Research Center for Optical Instruments, College of Optical Science and Engineering, Zhejiang University, Hangzhou, 310058, China
- Ningbo Research Institute, Zhejiang University, Ningbo, 315100, China
| | - Haibo Liu
- Ningbo Solartron Technology Co., Ltd, Ningbo, 315034, China
| | - Yubo Zhou
- Ningbo Solartron Technology Co., Ltd, Ningbo, 315034, China
| | - Yuxin Xing
- Centre for Optical and Electromagnetic Research, National Engineering Research Center for Optical Instruments, College of Optical Science and Engineering, Zhejiang University, Hangzhou, 310058, China
- Shanghai Institute for Advanced Study, Zhejiang University, Shanghai, 200135, China
| | - Zhe Chen
- Ningbo Solartron Technology Co., Ltd, Ningbo, 315034, China
| | - Shanhui Fan
- E. L. Ginzton Laboratory, and Department of Electrical Engineering, Stanford University, Stanford, CA, 94305, USA
| | - Julian Evans
- Centre for Optical and Electromagnetic Research, National Engineering Research Center for Optical Instruments, College of Optical Science and Engineering, Zhejiang University, Hangzhou, 310058, China
| | - Sailing He
- Centre for Optical and Electromagnetic Research, National Engineering Research Center for Optical Instruments, College of Optical Science and Engineering, Zhejiang University, Hangzhou, 310058, China
- Ningbo Research Institute, Zhejiang University, Ningbo, 315100, China
- JORCEP, School of Electrical Engineering, Royal Institute of Technology (KTH), Stockholm, S-100 44, Sweden
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