A simple, accurate, and universal method for characterizing and comparing radiative cooling materials and devices

Fan, Fan; Xu, Dikai; Zhu, Yazhu; Tan, Guofu; Zhao, Dongliang

doi:10.1016/j.ijheatmasstransfer.2022.123494

Cited by 14 publications

(4 citation statements)

References 38 publications

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“…The uncovered surface was limited to < 3 °C while the SFP achieved up to 6 °C below ambient, due to the decrease in parasitic heating by the insulating SFP. To quantify the reduction in the parasitic heating rate, the parasitic heat transfer coefficients were measured with and without the SFP, using the method described by Fan et al 35 In this method, the cooling power at ambient temperature and the maximum temperature drop are measured simultaneously with two identical devices. The uncovered 3M ESR surface was found to have a parasitic heat transfer coefficient of h = 8.1 W m −2 K −1 .…”

Section: Resultsmentioning

confidence: 99%

All-day passive radiative cooling using common salts

Reale Batista,

Troksa,

Eshelman

et al. 2023

Mater. Horiz.

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Section: Resultsmentioning

confidence: 99%

All-day passive radiative cooling using common salts

Reale Batista,

Troksa,

Eshelman

et al. 2023

Mater. Horiz.

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“…The polystyrene lid is coated with a highly reflective white layer, and the box is wrapped in aluminum foil. Note that this setup allows for simultaneously measuring both TDrop and PCool, which is fundamental to compare and characterize passive radiative cooling materials under the same environmental conditions [41].…”

Section: Outdoor Testsmentioning

confidence: 99%

Radiative cooling performance of a modified paint formulation with an integrated UV and convection shielding layer

Lio,

Levorin,

Erdogan

et al. 2024

Preprint

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Passive radiative cooling (PRC) technology promises to reduce a significant fraction of our energy needs and carbon footprint associated with cooling. Among different approaches, paint-like systems present several advantages in cost-effectiveness, scalability, and application ease. We report on a PRC system consisting of a paint mixture modified with 50 %wt glass bubbles and a top polypropylene-polyethylene-polypropylene (PP-PE-PP) film typically used as a battery separator. The resulting material exhibits a solar reflectance of 94 % and an absorption (evaluated by Attenuated Total Reflectance spectroscopy) with a peak at 10 µm of 60 %. The addition of the glass bubbles and the top film increases the paint reflectance over the solar spectrum and the UV, thanks to the nanoporous PP-PE-PP film (NPF), while allowing most thermal radiation through, shielding from convection, and making the coating more easily washable. The material has been tested under realistic outdoor conditions, checking the different performance obtained when sticking the PP-PE-PP film directly onto the wet paint layer or by using it as a separate windshield enclosing the sample test chamber. Despite its high solar reflectance, no radiative cooling is observed with respect to ambient temperature during the peak hours (solar irradiation >500 W m −2). Below this threshold, a temperature drop of −3 °C and a cooling power exceeding 100 W m−2 is observed. Notably, even using a visibly opaque convection shield, the configuration where the PP-PE-PP film seals the sample results in a substantial overheating of the air pocket surrounding the sample , which is detrimental to obtaining a temperature drop with respect to the true ambient temperature.

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“…The uncovered surface was limited to < 3 °C while the SAP achieved up to 6 °C below ambient, due to the decrease in parasitic heating by the insulating SAP. To quantify the reduction in the parasitic heating rate, the parasitic heat transfer coefficients were measured with and without the SAP, using the method described by Fan et al [35] In this method, the cooling power at ambient temperature and the maximum temperature drop are measured simultaneously with two identical devices. The uncovered 3M ESR surface was found to have a parasitic heat transfer coefficient of h = 8.1 W m -2 K -1 .…”

Section: Outdoor Testingmentioning

confidence: 99%

All-day passive radiative cooling using common salts

Batista

Troksa

Eshelman

et al. 2023

Preprint

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Radiative cooling materials continue to underperform compared to their theoretical potential due to parasitic heating from contact with ambient air. Solutions to this problem are expensive or complex to fabricate. Here, a potentially inexpensive, simply fabricated material that improves cooling performance by reducing parasitic heating was created using naturally abundant salts. NaCl and KCl are not typically considered for radiative cooling because of their high hygroscopicity and low mechanical strength; however, these compounds are highly infrared-transparent and can be fabricated into aerogel-like structures to provide thermally insulating properties. Salt aerogels, described herein, scattered (reflected) visible light, transmitted infrared radiation, and provided thermal insulation. They were packaged into mechanical supporting panels to avoid physical disruption and the nanostructure was stabilized to moisture by adding anti-caking agent. The panels were able to keep an underlying surface below ambient temperature for a full 24-hour cycle and reduced parasitic heating rate by more than half (compared to an uncovered surface). The panels were able to cool a variety of underlying surfaces, even highly absorbing surfaces that are normally well above ambient temperature during the day. This work demonstrates an affordable, easily produced, electricity-free cooling technology with potential to be manufactured for large-scale practical applications.

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A simple, accurate, and universal method for characterizing and comparing radiative cooling materials and devices

Cited by 14 publications

References 38 publications

All-day passive radiative cooling using common salts

All-day passive radiative cooling using common salts

Radiative cooling performance of a modified paint formulation with an integrated UV and convection shielding layer

All-day passive radiative cooling using common salts

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