{"paper_id":"00ffb818-24ce-403d-9f76-cfdc2b148de4","body_text":"Optimizing Thermal Radiation Control with Ultra-Broadband Metamaterials for High Passive Radiative Cooling Efficiency | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Optimizing Thermal Radiation Control with Ultra-Broadband Metamaterials for High Passive Radiative Cooling Efficiency Tesfaye Feyisa, Abebe Belay, Fekadu Tolessa, Kusse Kudishe, Umer sherefedin, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6718827/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 04 Dec, 2025 Read the published version in Scientific Reports → Version 1 posted 17 You are reading this latest preprint version Abstract Managing high energy consumption and thermal energy has become crucial for ensuring a sustainable and stable environment. Recently, passive radiative cooling (PRC) has emerged as an innovative method for reducing environmental energy density without requiring external energy input. This study focused on three wavelength ranges: 2.5–5 µm, 8–13 µm, and 16–27 µm, to optimize net cooling power. We acquired the optical and electrical properties of the materials utilized in this study through density functional theory (DFT). A cylinder-centered honeycomb structure was designed as a spectrally selective emitter by using Finite Element Method (FEM) method to enhance radiative properties. We analyzed how geometric parameters affect absorbance and emissivity performance. With the optimal geometry, we achieved a net cooling power of 150.4 W/m² under 994 W/m² of direct solar irradiation during the day. At night, in the absence of sunlight, the net cooling power increased to 198 W/m². The system reached equilibrium temperatures of 256 K during the day and 244 K at night, assuming an ambient temperature of 300 K. Even when considering parasitic convection and conduction, the cooler successfully maintained sub-ambient temperatures. Furthermore, the designed cooler exhibited polarization independence and high emissivity across a wide range of incidence angles (from 0° to 75°). Earth and environmental sciences/Climate sciences Earth and environmental sciences/Environmental sciences Physical sciences/Energy science and technology Physical sciences/Materials science Physical sciences/Optics and photonics Physical sciences/Physics/Electronics photonics and device physics Physical sciences/Physics/Optical physics Electronic structure Metamaterial Solar irradiation Selective-emissivity Atmospheric Window Radiative Cooling Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 04 Dec, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 12 Aug, 2025 Reviews received at journal 10 Aug, 2025 Reviews received at journal 08 Aug, 2025 Reviewers agreed at journal 06 Aug, 2025 Reviews received at journal 05 Aug, 2025 Reviewers agreed at journal 01 Aug, 2025 Reviewers agreed at journal 31 Jul, 2025 Reviewers agreed at journal 31 Jul, 2025 Reviewers agreed at journal 31 Jul, 2025 Reviewers agreed at journal 30 Jul, 2025 Reviewers agreed at journal 30 Jul, 2025 Reviewers agreed at journal 29 Jul, 2025 Reviewers agreed at journal 29 Jul, 2025 Reviewers invited by journal 29 Jul, 2025 Editor assigned by journal 13 Jun, 2025 Submission checks completed at journal 11 Jun, 2025 First submitted to journal 11 Jun, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-6718827\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Article\",\"associatedPublications\":[],\"authors\":[{\"id\":493142860,\"identity\":\"d7cee626-2a6c-42dc-8f90-2b354767fe3e\",\"order_by\":0,\"name\":\"Tesfaye 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Recently, passive radiative cooling (PRC) has emerged as an innovative method for reducing environmental energy density without requiring external energy input. This study focused on three wavelength ranges: 2.5\\u0026ndash;5 \\u0026micro;m, 8\\u0026ndash;13 \\u0026micro;m, and 16\\u0026ndash;27 \\u0026micro;m, to optimize net cooling power. We acquired the optical and electrical properties of the materials utilized in this study through density functional theory (DFT). A cylinder-centered honeycomb structure was designed as a spectrally selective emitter by using Finite Element Method (FEM) method to enhance radiative properties. We analyzed how geometric parameters affect absorbance and emissivity performance. With the optimal geometry, we achieved a net cooling power of 150.4 W/m\\u0026sup2; under 994 W/m\\u0026sup2; of direct solar irradiation during the day. At night, in the absence of sunlight, the net cooling power increased to 198 W/m\\u0026sup2;. 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