Optimization of hydrochromic properties in hygroscopic salt-porous composites: Toward applications in atmospheric water harvesting and smart window

Yue Fei, Tao Wu, Bin Xu, Yan-feng Huang, Xing-ni Chen and Gang Pei

Energy, 2025, vol. 334, issue C

Abstract: Hygroscopic salt-porous composites exhibit significant application value in atmospheric water harvesting and smart windows due to unique hydrochromic properties. However, their potential in passive atmospheric water harvesting and energy-saving windows requires further exploration, and systematic design guidelines for hydrochromic material parameters remain lacking. This study took LiCl/LiBr-SiO2 porous composites as an example to explore hydrochromic behavior and quantitatively evaluated effects of matrix structure parameters and hygroscopic salt types on hydrochromic performance. Results show that this material has characteristics of optical switching between high reflectance in initial state of water adsorption (Rsolar) and high transmittance in equilibrium state (Tsolar). As matrix thickness increases, Rsolar rises while Tsolar decreases. The thickness design of 50 ± 20 μm can meet the synergistic optimization of Rsolar and Tsolar by balancing light scattering and transmission paths. When matrix porosity is 0.8, the effective refractive index difference within the material and the number of scattering interfaces reach optimal balance, resulting in a peak optical modulation effect (ΔTsolar), with Rsolar and Tsolar respectively reaching extreme values. Furthermore, LiBr-porous composites are more suitable for scenarios dominated by optical modulation in medium humidity environments due to superior dynamic refractive index matching effect, achieving a 27.3 % relative improvement in ΔTsolar compared to LiCl-porous composites. LiCl-porous composites are more suitable for scenarios with high moisture absorption requirements in extreme humidity environments, achieving a 32.6 % relative improvement in equilibrium water absorption compared to LiBr-porous composites. This work provides quantitative theoretical guidelines for material design of hydrochromic energy-saving windows and pure passive atmospheric water harvesting.

Keywords: Hygroscopic salt-porous composites; Hydrochromic; Atmospheric water harvesting; Intelligent energy-saving window; Optical modulation (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:334:y:2025:i:c:s036054422503484x

DOI: 10.1016/j.energy.2025.137842

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