Optically Modulated Passive Broadband Daytime Radiative Cooling Materials Can Cool Cities in Summer and Heat Cities in Winter

Khan, Ansar; Carlosena, Laura; Feng, Jie; Khorat, Samiran; Khatun, Rupali; Doan, Quang-Van; Santamouris, Mattheos

doi:10.3390/su14031110

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Optically Modulated Passive Broadband Daytime Radiative Cooling Materials Can Cool Cities in Summer and Heat Cities in Winter

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Department of Geography, Lalbaba College, University of Calcutta, Howrah 711202, India

Department of Engineering, Arrosadia Campus, Public University of Navarra (UPNA), 31006 Pamplona, Spain

Faculty of Built Environment, University of New South Wales, Sydney, NSW 2052, Australia

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Department of Geography, University of Calcutta, Kolkata 700019, India

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School of Environmental Studies, Jadavpur University, Kolkata 700032, India

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Centre for Computational Sciences, University of Tsukuba, Tsukuba 305 8577, Ibaraki, Japan

Author to whom correspondence should be addressed.

Academic Editors: Steve Kardinal Jusuf, Soh Chew Beng, Elsa Feng and Szu-Cheng Chien

Sustainability 2022, 14(3), 1110; https://doi.org/10.3390/su14031110

Received: 19 December 2021 / Revised: 14 January 2022 / Accepted: 15 January 2022 / Published: 19 January 2022

(This article belongs to the Special Issue Pro-environmental Decisions: Sustainable Use of Urban Rooftops)

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Abstract

Broadband passive daytime radiative cooling (PDRC) materials exhibit sub-ambient surface temperatures and contribute highly to mitigating extreme urban heat during the warm period. However, their application may cause undesired overcooling problems in winter. This study aims to assess, on a city scale, different solutions to overcome the winter overcooling penalty derived from using PDRC materials. Furthermore, a mesoscale urban modeling system assesses the potential of the optical modulation of reflectance (ρ) and emissivity (ε) to reduce, minimize, or reverse the overcooling penalty. The alteration of heat flux components, air temperature modification, ground and roof surface temperature, and the urban canopy temperature are assessed. The maximum decrease of the winter ambient temperature using standard PDRC materials is 1.1 °C and 0.8 °C for daytime and nighttime, respectively, while the ρ+ε-modulation can increase the ambient temperature up to 0.4 °C and 1.4 °C, respectively, compared to the use of conventional materials. Compared with the control case, the maximum decrease of net radiation inflow occurred at the peak hour, reducing by 192.7 Wm⁻² for the PDRC materials, 5.4 Wm⁻² for ρ-modulated PDRC materials, and 173.7 Wm⁻² for ε-PDRC materials; nevertheless, the ρ+ε-modulated PDRC materials increased the maximum net radiation inflow by 51.5 Wm⁻², leading to heating of the cities during the winter. View Full-Text

Keywords: urban heat mitigation; broadband radiative cooling emitters; overcooling; optical modulation; WRF-SLUCM; Kolkata

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MDPI and ACS Style

Khan, A.; Carlosena, L.; Feng, J.; Khorat, S.; Khatun, R.; Doan, Q.-V.; Santamouris, M. Optically Modulated Passive Broadband Daytime Radiative Cooling Materials Can Cool Cities in Summer and Heat Cities in Winter. Sustainability 2022, 14, 1110. https://doi.org/10.3390/su14031110

AMA Style

Khan A, Carlosena L, Feng J, Khorat S, Khatun R, Doan Q-V, Santamouris M. Optically Modulated Passive Broadband Daytime Radiative Cooling Materials Can Cool Cities in Summer and Heat Cities in Winter. Sustainability. 2022; 14(3):1110. https://doi.org/10.3390/su14031110

Chicago/Turabian Style

Khan, Ansar, Laura Carlosena, Jie Feng, Samiran Khorat, Rupali Khatun, Quang-Van Doan, and Mattheos Santamouris. 2022. "Optically Modulated Passive Broadband Daytime Radiative Cooling Materials Can Cool Cities in Summer and Heat Cities in Winter" Sustainability 14, no. 3: 1110. https://doi.org/10.3390/su14031110

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Optically Modulated Passive Broadband Daytime Radiative Cooling Materials Can Cool Cities in Summer and Heat Cities in Winter

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