Roof-integrated radiative air-cooling system to achieve cooler attic for building energy saving

Zhao, Dongliang; Aili, Ablimit; Yin, Xiaobo; Tan, Gang; Yang, Ronggui

doi:10.1016/j.enbuild.2019.109453

Roof-integrated radiative air-cooling system to achieve cooler attic for building energy saving

Journal Article · Mon Sep 23 00:00:00 EDT 2019 · Energy and Buildings

DOI:https://doi.org/10.1016/j.enbuild.2019.109453· OSTI ID:1799028

Zhao, Dongliang ^[1]; Aili, Ablimit ^[2]; Yin, Xiaobo ^[2]; Tan, Gang ^[3]; Yang, Ronggui ^[2]

Univ. of Colorado, Boulder, CO (United States); OSTI
Univ. of Colorado, Boulder, CO (United States)
Univ. of Wyoming, Laramie, WY (United States)

The building attic usually subjects to substantial solar heat gain and has much higher temperature compared to the conditioned living space during the day, especially in summer and in hot areas. Reducing attic temperature can reduce cooling energy consumption in buildings. However, conventional techniques such as cool roof or attic ventilation, suffer from either heating penalty in winter or limited attic temperature reduction. In this work, a new roof-integrated radiative air-cooling system is introduced, which couples radiative sky cooling with attic ventilation to reduce attic temperature. A radiative air cooler with 1.08 m² surface area is constructed using a recently developed daytime radiative sky cooling metamaterial [Zhai et al., Science 355, pp. 1062–1066, 2017]. Experimental tests show that sub-ambient air cooling is achieved throughout 24-h day-and-night cycle in a summer day with clear sky conditions. Depending on air flow rates, measured sub-ambient temperature reductions of air are 5–8°C at night and 3–5°C at noon under direct sunlight, respectively. An in-house model is first developed for the radiative air-cooling system, the model is then coupled with EnergyPlus to study annual energy saving of buildings. The performance of the radiative air-cooling system is compared with three reference systems: shingle roof, attic ventilation, and cool roof. Results show that for a single-family house, attic temperature can be substantially reduced by 15.5–21.0°C, varying with attic insulation level, compared to shingle roof on typical summer days. Compared to a shingle roof (solar reflectance 0.25, thermal emittance 0.9) residential building with attic insulations of R-30 (RSI-5.28), R-10 (RSI-1.76), and R-0.8 (RSI-0.14), the roof-integrated radiative air-cooling system can achieve annual cooling energy savings of 0.4–1.5 kWh/m² (4.6–18.8%), 1.2–3.6 kWh/m² (10.2–41.4%), and 3.7–11.8 kWh/m² (26.5–76.1%) respectively.

View Accepted Manuscript (DOE)

Research Organization:: Univ. of Colorado, Boulder, CO (United States)

Sponsoring Organization:: USDOE Advanced Research Projects Agency - Energy (ARPA-E)

Grant/Contract Number:: AR0000580

OSTI ID:: 1799028

Alternate ID(s):: OSTI ID: 1779558

Journal Information:: Energy and Buildings, Journal Name: Energy and Buildings Vol. 203; ISSN 0378-7788

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
attic cooling
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