Development of spectrally self-switchable cover with phase change material for dynamic radiative cooling

Su, Weiguang; Kang, Ruigeng; Cai, Pei; Hu, Mingke; Kokogiannakis, Georgios; Darkwa, Jo; Chen, Jun; Xu, Shuhui; Wang, Li

Abstract

Radiative cooling promises an effective strategy against global warming by sending waste heat to the deep universe in a passive manner. However, the mismatch between cooling supply and demand can significantly compromise the efficacy of spectrally-static radiative cooling devices in cold weather. Therefore, the present work introduced paraffin wax as the phase change material (PCM) to develop a spectrally self-switchable cover (SSC) for flexible radiative cooling. The transmittance of the paraffin wax at different temperatures, thicknesses and phases was characterized. In the UV-VIS-NIR band, the transmittance of the paraffin wax was over 90% in the liquid phase but below 5% in the solid phase. In the “atmospheric window” band, the transmission of the paraffin wax in the liquid phase was also much higher than that in the solid phase with a maximum difference of 41.1%. The optical constants of various paraffin waxes in solid and liquid phases were calculated according to the two-thickness inversion method. The average error of transmittance between the calculated and measured values was only 1.8% and 4% for the 0.19–1.1 μm and 8–13 μm bands, respectively. Moreover, the microstructure analysis of the solid-state paraffin wax revealed that the size of paraffin grains was around 10 μm with interlocking and irregular grain boundaries. The integrated multilayered-like structure resulted in a significant transmittance reduction of the solid-state paraffin wax. In the end, self-switchable PE-PCM-PE (polyethylene-phase change material-polyethylene) covers were prepared and spectrally characterized. The paraffin-based cover provided a new and low-cost candidate solution for achieving dynamic radiative cooling.

Citation

Su, W., Kang, R., Cai, P., Hu, M., Kokogiannakis, G., Darkwa, J., …Wang, L. (2023). Development of spectrally self-switchable cover with phase change material for dynamic radiative cooling. Solar Energy Materials and Solar Cells, 251, Article 112125. https://doi.org/10.1016/j.solmat.2022.112125

• Journal Article Type: Article
• Acceptance Date: Nov 20, 2022
• Online Publication Date: Nov 30, 2022
• Publication Date: Mar 1, 2023
• Deposit Date: Nov 25, 2022
• Publicly Available Date: Dec 1, 2023
• Journal: Solar Energy Materials and Solar Cells
• Print ISSN: 0927-0248
• Electronic ISSN: 1879-3398
• Publisher: Elsevier BV
• Peer Reviewed: Peer Reviewed
• Volume: 251
• Article Number: 112125
• DOI: https://doi.org/10.1016/j.solmat.2022.112125
• Keywords: Surfaces, Coatings and Films; Renewable Energy, Sustainability and the Environment; Electronic, Optical and Magnetic Materials
• Public URL: https://nottingham-repository.worktribe.com/output/14039077
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S0927024822005426?via%3Dihub
• Additional Information: Article Title: Development of spectrally self-switchable cover with phase change material for dynamic radiative cooling; Journal Title: Solar Energy Materials and Solar Cells; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.solmat.2022.112125