Reduction of Reflected Heat by Retroreflective Materials

Sakai, Hideki; Emura, Kazuo; Igawa, Norio

doi:10.3130/aijs.73.1239

Cited by 20 publications

(15 citation statements)

References 9 publications

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“…Sakai et al [32] and Yuan et al [33,34] estimated the solar reflectances of retroreflective test specimens by comparing their temperature rises under near-normal direct sunlight to those of non-retroreflective reference specimens, then subtracting near normal-hemispherical solar reflectance measured in a UV-vis-NIR spectrophotometer with integrating sphere. These studies used stationary specimens in their calorimetric trials.…”

Section: Methods C (Calorimeter and Spectrophotometer)mentioning

confidence: 99%

“…Retroreflectance can be assessed by (A) measuring retroreflection with coincident light source and light detector, such as those in a fiber spectrophotometer [20][21][22]; (B) measuring bi-directional reflectivity, or at least the angular distribution of reflected light, with a goniometer [23][24][25][26][27][28][29][30][31]; or (C) using calorimetry to gauge directional-hemispherical solar reflectance from temperature rise in the sun, then subtracting from this value directional-hemispherical solar reflectance measured in a spectrophotometer with fitted with an integrating sphere [32][33][34][35]. Method C works because perfectly retroreflected light escapes through the inlet port of the integrating sphere.…”

Section: Measurement Of Retroreflectancementioning

confidence: 99%

“…"high-intensity"), unmetallized microprism (also Type 3), and unmetallized cube corner microprism (Type 8 or Type 9; neither has a common name) [17][18][19][20]23,24,33,34,37]. Sakai et al [32] applied Method C (calorimeter and spectrophotometer) to measure near-normal (7° incidence) solar retroreflectances of 0.049 -0.129 for enclosed lens glass bead sheeting, 0.178 for an encapsulated lens glass bead sheet, and 0.235 -0.295 for microprismatic sheeting. Yuan et al [33] applied Method C to measure the near-normal (7° incidence) solar retroreflectances of a Type 3 encapsulated lens glass bead sheet (0.18 when new; 0.0072 after 25 months of natural exposure in Osaka, Japan) and a Type 9 microprismatic sheet (0.44 when new; 0.42 after 25 months).…”

Section: Retroreflective Materials 231 Retroreflective Sheeting Formentioning

confidence: 99%

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Design, characterization, and fabrication of solar-retroreflective cool-wall materials

Levinson

Chen

Slack

et al. 2020

Solar Energy Materials and Solar Cells

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Raising urban albedo increases the fraction of incident sunlight returned to outer space, cooling cities and their buildings. We evaluated the angular distribution of solar radiation incident on exterior walls in 17 U.S. climates to develop performance parameters for solar-retroreflective walls, then applied firstprinciple physics and ray-tracing simulations to explore designs. Our analysis indicates that retroreflective walls must function at large incidence angles to reflect a substantial portion of summer sunlight, and that this will be difficult to attain with materials that rely on total internal reflection. Gonio-spectrophotometer measurements of the solar spectral bi-directional reflectivity of a bicycle reflector showed little to no retroreflection at large incidence angles. Visual comparison of retroreflection to specular first-surface reflection for four different retroreflective safety films using violet and green lasers suggest their retroreflection to be no greater than 0.09 at incidence angles up to 45°, and no greater than 0.30 at incidence angles of up to 70°. Attempts to produce a two-surface retroreflector with orthogonal mirror grooves by cutting and polishing an aluminum block indicate that residual surface roughness impedes retroreflection. Ongoing efforts focus on forming orthogonal surfaces with aluminized Mylar film, a material with very high specular reflectance across the solar spectrum. We investigated (1) folding or stamping a free film; (2) adhering the film to a pre-shaped substrate; and (3) attaching the film to a flat ductile substrate, then shaping. The latter two methods were more successful but produced imperfect right angles.

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Section: Methods C (Calorimeter and Spectrophotometer)mentioning

confidence: 99%

Section: Measurement Of Retroreflectancementioning

confidence: 99%

Section: Retroreflective Materials 231 Retroreflective Sheeting Formentioning

confidence: 99%

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Design, characterization, and fabrication of solar-retroreflective cool-wall materials

Levinson

Chen

Slack

et al. 2020

Solar Energy Materials and Solar Cells

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“…Highly reflective materials (HRM) have been studied for possible use to mitigate the urban heat island as a building coating [7]. HRM can reflect solar energy, reduce solar radiation heat penetration into the urban canyon layer, and prevent some of the increase in urban surface temperature [8,9]. A research article has reported that the building surface temperature can be decreased about 10 • C by using highly reflective surfaces [10].…”

Section: Introductionmentioning

confidence: 98%

Development of a retro-reflective material as building coating and evaluation on albedo of urban canyons and building heat loads

Yuan

Farnham

Emura

2015

Energy and Buildings

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“…Structures of the roof, floor, exterior wall, and interior wall are shown in Table 1. Many studies and countermeasures to mitigate the UHI effects have also been implemented widely in Japan [24][25][26][27]. From 2010, HR roofing sheets were installed on the roofs of 70 schools in Osaka, Japan, to mitigate the UHI effect and reduce building energy consumption.…”

Section: Subject School and Hr Roofing Sheetmentioning

confidence: 99%

Highly Reflective Roofing Sheets Installed on a School Building to Mitigate the Urban Heat Island Effect in Osaka

2016

Self Cite

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Abstract:Currently, strategies to mitigate urban heat island (UHI) effects and reduce building energy consumption are implemented worldwide. In Japan, as an effective means of mitigating UHI effects and saving energy of buildings, highly reflective (HR) roofs have increasingly been used. In this study, in order to evaluate the effect of HR roofs on building energy conservation, we investigated the solar reflectivity of a subject school roof in Osaka, Japan, in which HR roofing sheets were installed on the roof from 2010. Additionally, monthly and annual thermal loads, including the cooling load and heating load of the top floor of the school, were calculated using the thermal load calculation software New HASP/ACLD-β. Comparing the calculated thermal loads of the school after HR roofing sheet installation to before, the annual thermal load decreased about 25 MJ/m 2 /year, and the cooling load decreased about 112 MJ/m 2 /year. However, the heating load increased about 87 MJ/m 2 /year in winter. To minimize the annual thermal load, thermal insulation of the roof was also considered to be used together with HR roofing sheets. Thermal load calculations showed that the combination of HR roofing sheets and thermal insulation can be effective in further reducing the annual thermal load.

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Reduction of Reflected Heat by Retroreflective Materials

Cited by 20 publications

References 9 publications

Design, characterization, and fabrication of solar-retroreflective cool-wall materials

Design, characterization, and fabrication of solar-retroreflective cool-wall materials

Development of a retro-reflective material as building coating and evaluation on albedo of urban canyons and building heat loads

Highly Reflective Roofing Sheets Installed on a School Building to Mitigate the Urban Heat Island Effect in Osaka

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