From flat to structured : geometry-driven dual-mode radiative emitters for simultaneous hotspot cooling and water harvesting

Poredoš, Primož (author), Silva-Oelker, Gerardo (author), Trajkovski, Dejan (author), Wilson Marangattil, Higgins (author), Ali, Abdallah Y.M. (author), Žižak, Tej (author), Zavrl, Eva (author), Arkar, Ciril (author), Medved, Sašo (author), Domjan, Suzana (author)

Radiative cooling has been developed for two largely separate functions: passive thermal management and atmospheric water harvesting (AWH). Combining them on a single surface under an imposed heat load is intrinsically difficult, as hotspot cooling raises the emitter temperature, whereas condensation requires sustained sub-dew-point regions. Here we establish, to our knowledge, a previously unreported geometry-driven co-functional regime in which a localized hotspot is coupled to an extended planar or pyramidal radiative emitter. Lateral heat spreading creates a warm, dry zone near the hotspot while preserving cooler peripheral regions for dew formation, allowing the same passive platform to reject heat and harvest water simultaneously. We combine angle-resolved optical characterization, raytracing, coupled heat and mass transfer modelling, and outdoor experiments. At a hotspot heat flux of 1021 W m$^{−2}$, the largest planar emitter and 45° pyramidal emitter retain dew fluxes of 9.3 and 7.9 g m▫$^{−2}$▫ h▫$^{−1}$▫, respectively, while lowering the near-hotspot temperature by more than 45 °C relative to a non-concentrated control. At 1500 W m$^{−2}$, the same architectures keep the hotspot below 20 °C, whereas the control approaches 85 °C. Finally, an experiment-calibrated global assessment further identifies where this regime is climatically accessible. These results provide a general framework for the passive co-management of localized heat and atmospheric water harvesting.

• Language: English
• Keywords: radiative sky cooling materials, atmospheric water harvesting, hotspot cooling, heat and mass transfer, ray tracing, numerical simulations, optical characteristics of materials
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: Str. 7064-7088
• Numbering: Vol. 19, iss. 20
• PID: 20.500.12556/RUL-190055
• UDC: 536.24:628.116
• ISSN on article: 1754-5692
• DOI: 10.1039/d6ee04674f
• COBISS.SI-ID: 301807875
• Publication date in RUL: 21.10.2026

Record is a part of a journal

• Title: Energy & environmental science
• Publisher: Royal Society of Chemistry
• ISSN: 1754-5692
• COBISS.SI-ID: 514856729

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: dnevno-sevalni materiali, pridobivanje vode iz atmosfere, hlajenje vročih točk, prenos toplote in snovi, sledenje žarkom, numerične simulacije, optične lastnosti materialov