All-day passive radiative cooling using common salts

Journal Article · 28 September 2023 · Materials Horizons

DOI: https://doi.org/10.1039/d3mh01139a · OSTI ID:2007567

Reale Batista, Mariana Desireé  ^[1]; Troksa, Alyssa L.  ^[1]; Eshelman, Hannah V.  ^[1]; Bagge-Hansen, Michael  ^[1]; Roehling, John D.  ^[1]

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1. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Radiative cooling materials underperform compared to their theoretical potential due to parasitic heating from contact with ambient air. Solutions to this problem can be 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 foam structures to provide thermally insulating properties. The salt foams, 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 an 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.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); USDOE Laboratory Directed Research and Development (LDRD) Program
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 2007567
• Alternate ID(s): OSTI ID: 2204952
• Report Number(s): LLNL-JRNL-845039; 1068492
• Journal Information: Materials Horizons, Journal Name: Materials Horizons; ISSN 2051-6347
• Publisher: Royal Society of ChemistryCopyright Statement
• Country of Publication: United States
• Language: English