Utilizing micro-nano dual-sized particles to enhance solar reflection in constructing energy-saving hydrogel for daytime passive cooling

Shuai Zhao, Hao Tu, Jianjun Zhang, Qifeng Tang, Minghuan Hou, Bolin Xie, Xin Xiao and Jian Wang

Renewable Energy, 2025, vol. 249, issue C

Abstract: As a passive cooling technology, evaporative cooling and radiative cooling have the advantages of zero carbon footprint and zero energy consumption, making them one of the effective solutions to reduce the dependence on energy-intensive active cooling technologies such as compression refrigeration. In this work, nano-micro particles/polyvinyl alcohol/polyvinylpyrrolidone/polyethylene glycol hydrogels (NMPs/PVA/PVP/PEG) were prepared by using hydrogels as efficient solar evaporators to construct optical reflective layers with different scale fillers for efficient passive cooling. NMPs/PVA/PVP/PEG has strong solar reflectance (∼89 %) and high emissivity close to a mid-infrared blackbody (∼97 %). Simultaneously, NMPs/PVA/PVP/PEG have good hydration and evaporation properties, and the swollen hydrogel combines evaporative cooling with radiative cooling, achieving an effective cooling of 18.9 °C in an outdoor environment with direct sunlight, with a theoretical total cooling power of 234.24 W/m2. After hydration for 30 min, NMPs/PVA/PVP/PEG can achieve a temperature 17 °C lower than the temperature of the uncovered cavity under direct sunlight of 800 W/m2. Specially, experiments have demonstrated the potential and development prospects of NMPs/PVA/PVP/PEG in the preservation of frozen foods, and through energy simulations, NMPs/PVA/PVP/PEG can save approximately 20.84 MJ/m2 of cooling energy annually, which is of great significance for further exploring the sustainable development of refrigeration technology.

Keywords: Radiation cooling; Evaporative cooling; Synergistic effect; Size effect; Cooling power; Energy saving (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:249:y:2025:i:c:s0960148125009358

DOI: 10.1016/j.renene.2025.123273

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