On the energy potential of daytime radiative cooling for urban heat island mitigation

Carlosena, Laura; Ruiz–Pardo, Álvaro; Feng, Jie; Irulegi, O.; Hernández-Minguillón, Rufino; Santamouris, M.

doi:10.1016/j.solener.2020.08.015

Cited by 45 publications

(14 citation statements)

References 60 publications

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“…Therefore, the choice of the appropriate DRC type depends on the boundary conditions. [120,121] Ensuring the high cooling performance of DRCs in the long run and their compatibility under real-life conditions, while maintaining easy and low-cost production and scalability, are the primary prerequisites that need to be addressed currently.…”

Section: Daytime Radiative Cooling Application: Research Progress And...mentioning

confidence: 99%

Toward the Scaling up of Daytime Radiative Coolers: A Review

Kousis,

Pisello

2023

Advanced Optical Materials

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Daytime Radiative Cooling (DRC) is a highly effective passive cooling technique that holds great potential for enhancing energy efficiency and promoting decarbonization. Several Daytime Radiative Coolers (DRCs) are reported in the literature to highly reflect shortwave radiation and emit thermal radiation, either specifically in the Atmospheric Window (AW) wavelengths (8–13 µm) (Selective DRCs) or in both AW and non‐AW wavelengths (Broadband DRCs). This review presents the advancements in the six key categories of DRCs identified in the literature based on their design characteristics: i) multilayer DRCs, ii) metamaterial DRCs, iii) randomly distributed particle DRC structures, iv) porous DRCs, v) colored DRCs, and vi) adaptive DRCs. The review discusses their main attributes in terms of their demonstrated thermo‐optical performance. Research gaps include the need for real‐life studies to investigate scaling up DRCs in the built environment and their effects on indoor thermal comfort and air temperature reduction. Finally, an eight‐step feedback‐loop scheme is proposed to establish efficient design and implementation protocols for DRC materials in the built environment.

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Section: Daytime Radiative Cooling Application: Research Progress And...mentioning

confidence: 99%

Toward the Scaling up of Daytime Radiative Coolers: A Review

Kousis,

Pisello

2023

Advanced Optical Materials

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“…Since heat is absorbed by water vapor at specific wavelengths, clouds and precipitable water vapor operate as a barrier to heat transmission, reducing outgoing radiation through the atmospheric band and increasing the effective temperature of the sky. Previous research conducted a sensitivity analysis on the impact of wavelength emissivity [61] and climate parameters [23] on the ability to achieve daytime radiative cooling.…”

Section: Study Cases: Kolkata Metropolitan Areamentioning

confidence: 99%

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

et al. 2022

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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.

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“…A range of heat mitigation technologies has been proposed to combat environmental consequences associated with extreme urban heat. These strategies fall under the broad umbrella of green infrastructure (e.g., urban lawns, trees, and green roofs (GRs)) and biophysical, or engineered, materials (e.g., cool materials (CMs)), including pavements and roofs, and super-cool broadband radiative coolers (Akbari et al, 2001;Baniassadi et al, 2019;Carlosena et al, 2020;Chow et al, 2012;Georgescu et al, 2013Georgescu et al, , 2014Krayenhoff et al, 2018;Santamouris, 2014aSantamouris, , 2014bSantamouris & Yun, 2020;Takebayashi & Moriyama, 2007). Broadband radiative coolers are emerging as a promising technology (Zhao et al, 2019), in large part because most heat mitigation technologies reduce daytime urban temperatures but have minimal impact during the evening and nighttime hours (Georgescu, 2015).…”

Section: Introductionmentioning

confidence: 99%

Exploring the Meteorological Impacts of Surface and Rooftop Heat Mitigation Strategies Over a Tropical City

et al. 2023

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Different heat mitigation technologies have been developed to improve the thermal environment in cities. However, the regional impacts of such technologies, especially in the context of a tropical city, remain unclear. The deployment of heat mitigation technologies at city‐scale can change the radiation balance, advective flow, and energy balance between urban areas and the overlying atmosphere. We used the mesoscale Weather Research and Forecasting model coupled with a physically based single‐layer urban canopy model to assess the impacts of five different heat mitigation technologies on surface energy balance, standard surface meteorological fields, and planetary boundary layer (PBL) dynamics for premonsoon typical hot summer days over a tropical coastal city in the month of April in 2018, 2019, and 2020. Results indicate that the regional impacts of cool materials (CMs), super‐cool broadband radiative coolers, green roofs (GRs), vegetation fraction change, and a combination of CMs and GRs (i.e., “Cool city (CC)”) on the lower atmosphere are different at diurnal scale. Results showed that super‐cool materials have the maximum potential of ambient temperature reduction of 1.6°C during peak hour (14:00 LT) compared to other technologies in the study. During the daytime hours, the PBL height was considerably lower than the reference scenario with no implementation of strategies by 700 m for super‐cool materials and 500 m for both CMs and CC cases; however, the green roofing system underwent nominal changes over the urban area. During the nighttime hours, the PBL height increased by CMs and the CC strategies compared to the reference scenario, but minimal changes were evident for super‐cool materials. The changes of temperature on the vertical profile of the heat mitigation implemented city reveal a stable PBL over the urban domain and a reduction of the vertical mixing associated with a pollution dome. This would lead to crossover phenomena above the PBL due to the decrease in vertical wind speed. Therefore, assessing the coupled regional impact of urban heat mitigation over the lower atmosphere at city‐scale is urgent for sustainable urban planning.

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On the energy potential of daytime radiative cooling for urban heat island mitigation

Cited by 45 publications

References 60 publications

Toward the Scaling up of Daytime Radiative Coolers: A Review

Toward the Scaling up of Daytime Radiative Coolers: A Review

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

Exploring the Meteorological Impacts of Surface and Rooftop Heat Mitigation Strategies Over a Tropical City

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