A review of the application of radiative sky cooling in buildings: Challenges and optimization

Wu, Yunyi; Zhao, Hengxin; Sun, Hongli; Duan, Mengjie; Lin, Boqiang; Wu, Shuangdui

doi:10.1016/j.enconman.2022.115768

Cited by 46 publications

(11 citation statements)

References 148 publications

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“…The above studies discussed state-of-the-art solutions to change the solar transmittance of PV windows through thin films or gas layers with variable transmittance. In recent years, sky radiation cooling technology has been developing rapidly [85], and using semi-transparent cooling films in PV windows can reduce the cooling load of buildings. Tang et al [86] proposed a window that generates electricity during the daytime and utilizes sky radiant cooling during the nighttime and carried out the performance tests and the development of a MATLAB-based simulation program.…”

Section: Radiation-regulated Switchable Pv Windowsmentioning

confidence: 99%

Challenges and Optimization of Building-Integrated Photovoltaics (BIPV) Windows: A Review

Shi,

Zhu

2023

Sustainability

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PV windows are seen as potential candidates for conventional windows. Improving the comprehensive performance of PV windows in terms of electrical, optical, and heat transfer has received increasing attention. This paper reviews the development of BIPV façade technologies and summarizes the related experimental and simulation studies. Based on the results of the literature research, the average comprehensive energy-saving rate of BIPV façades can reach 37.18%. Furthermore, limitations and optimization directions of photovoltaic integrated shading devices (PVSDs), photovoltaic double-skin façades, and photovoltaic windows are presented. To improve the energy-saving potential of windows as non-energy efficiency elements of buildings, smart PV windows are proposed to be the key to breakthrough comprehensive performance. However, not all switchable windows concepts can be applied to PV windows. Typical studies on smart windows and PV windows are sorted out to summarize the challenges and optimization of smart PV window technical solutions. Considering the technological innovations in smart PV windows, two requirements of energy-saving materials and building envelopes are put forward. The advances in materials and the building envelope are complementary, which will promote the sophistication and promotion of solar building technology.

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Section: Radiation-regulated Switchable Pv Windowsmentioning

confidence: 99%

Challenges and Optimization of Building-Integrated Photovoltaics (BIPV) Windows: A Review

Shi,

Zhu

2023

Sustainability

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“…The long-wave radiation between the sky and the building has an impact on the building's energy demand [76]. Some studies considered the sky as a cooling source for radiative cooling, which can significantly reduce the roof surface temperature and building cooling load [77]. The second factor is the sky view factor (SVF), which refers to the proportion of visible sky above the observation point.…”

Section: Skymentioning

confidence: 99%

A Review on the Impact of Outdoor Environment on Indoor Thermal Environment

Lin,

Huang,

Yang

et al. 2023

Buildings

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Outdoor environment exchanges heat with indoor environment, enabling pollutants to infiltrate indoors, affecting buildings’ energy efficiency, comfort, and indoor air quality. Investigating the impact of the outdoor environment on the indoor thermal environment is crucial. Firstly, this paper reviews the coupling method to link the outdoor environment with the indoor environment. Secondly, it examines the impact of the outdoor physical environment, including neighboring buildings, greening, road surface, water body, and sky, on the indoor thermal environment. During the hottest summer, an increase of 17% in trees can reduce indoor temperature by 1.1 °C. Thirdly, the impact of weather conditions, including outdoor temperature, outdoor humidity, external wind, global warming, extreme weather conditions, and solar radiation, on the indoor thermal environment is studied. Due to global warming, cooling energy consumption and heating energy consumption in 2050 could increase by 223% to 1050%, and heating demand could decrease by 36% to 58%. Finally, the impact of outdoor air pollution on indoor environment and energy consumption is analyzed. For every 75 μg/m3 increase in PM2.5 concentration, average power consumption could increase by 11.2%. Recommendations for future research are provided. This study contributes to the understanding of the outdoor–indoor thermal relationship and offers insights into enhancing indoor thermal comfort and reducing building energy consumption.

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“…In this model, thermal radiation is considered as an energy transfer between the boundary and the heat source, and the medium is not involved in the radiation (a transparent medium) [21,22]. The effective radiation force at the surface of the object is…”

Section: 3 Surface-to-surface Radiative Modelmentioning

confidence: 99%

The Mathematical Modeling and Performance of Sky Radiative Coolers

Zhuang,

Yang,

Xie

et al. 2023

Buildings

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Sky radiative cooling is a kind of passive cooling technology that uses the “atmospheric window” to emit the object’s own heat to the low temperature of outer space; this technology has low energy consumption, no pollution, and other useful characteristics, so in recent years it has attracted widespread attention. The cooling effect of the sky radiative cooler is mainly affected by the constantly changing outdoor ambient temperature. In addition, the structure of the radiative cooler itself also means that its radiative cooling power undergoes obvious changes. Here, we utilized COMSOL simulation software to establish a numerical heat transfer model for radiative cooling, aimed at investigating the influencing factors on the sky radiative cooler and methods to enhance the structure of the radiative cooling. This study discusses outdoor ambient wind speed, the inlet flow rate of the cooler, installation angle of the cooler, and different cooler structures. Based on simulation results, it is observed that, for varying wind speeds, when the ambient radiation temperature is higher than the surface temperature of the cooler, a larger ambient wind speed leads to a poorer refrigeration effect. The maximum temperature difference in surface temperature at wind speeds of 0 m/s and 4 m/s is 0.59 °C. When the ambient temperature is lower than the surface temperature of the cooler, a smaller wind speed results in a greater net refrigeration power. The maximum temperature difference in this scenario is 0.32 °C. The net refrigeration power of the radiative cooler increases with an increase in water flow rate. As the water flow rate increases from 0 L/min to 5 L/min, the net refrigeration power increases from 25 W/m2 to 200 W/m2 and gradually stabilizes. Considering the radiative impact of the cooler on the surrounding environment, as the installation angle increases from 0° to 90°, the surface temperature of the cooler first increases and then decreases, reaching its highest temperature of 29.26 °C at 45°. The surface temperature of the cooler varies with the thickness of the air sandwich, increasing from 1 cm to 12 cm, and then decreasing. The lowest temperature of 23.4 °C is achieved at a thickness of 8 cm. The increase in the fin structure on the surface of the radiative cooler leads to a decrease in its refrigeration performance, and the difference between the inlet and outlet temperatures of the radiative cooler with a flat plate structure is always greater than that of the finned plate, and the difference in the average radiance is 23.52 W/m2. Finally, the energy-saving effect of the sky radiative cooling composite system is analyzed. Taking a typical small office building as an example, an energy consumption analysis model is set up, and the energy consumption of the composite system is simulated in four cities with different climates, using EnergyPlus software (version 8.6); the system’s power consumption is the largest in hot and humid climates. Compared with the traditional vapor-compression refrigeration system, the composite system reduces air conditioning power consumption by 25.7%, 32.5%, 37.1%, and 44.8% in Guangzhou, Shanghai, Jinan, and Shenyang, respectively. The main innovations of this paper include analyzing and studying the influence of the tilt angle change of the radiative plate on the refrigeration performance of the cooler and the relationship between the surrounding buildings, adding air sandwiches and ribs to the radiative cooler to analyze the influence of convective heat transfer on the refrigeration effect, which plays a guiding role in the design and research of the sky radiative cooler.

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A review of the application of radiative sky cooling in buildings: Challenges and optimization

Cited by 46 publications

References 148 publications

Challenges and Optimization of Building-Integrated Photovoltaics (BIPV) Windows: A Review

Challenges and Optimization of Building-Integrated Photovoltaics (BIPV) Windows: A Review

A Review on the Impact of Outdoor Environment on Indoor Thermal Environment

The Mathematical Modeling and Performance of Sky Radiative Coolers

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