Standard Test Methods for Rating of Solar Reflectance of Built-Up Surfaces and Potential Use of Satellite Remote Sensors

Abstract

More and more attention is being paid to the solar reflectance of built-up surfaces due to its influence on the summer heating of buildings and urban areas and the consequent effects on energy needs for air conditioning, as well as on the peak load of the electric grid. Several standard test methods are available for measuring solar reflectance in the laboratory or in the field, based on different devices and approaches. A convergence of some methods has been achieved by rating programs in the U.S. and, more recently, in Europe and other areas. However, laboratory or field measurements are impractical for characterizing a large number of urban surfaces—whether it is for identifying critical issues, developing policies, or verifying compliance with building requirements. In this regard, satellite remote sensors have recently become available, through which it is possible to estimate the reflectance of roof and pavement surfaces thanks to a spatial resolution that is suitable for identifying and characterizing individual built-up surfaces. In the present paper, the most-used standard test methods for rating of solar reflectance are reviewed. Subsequently, some publicly accessible satellite sensors are examined, through which comparable measurements could be obtained.

Assessing Satellite Data’s Role in Substituting Ground Measurements for Urban Surfaces Characterization: A Step towards UHI Mitigation

“…RMSE serves as a measure of the discrepancy between measured and predicted values, with lower RMSE values indicating higher measurement accuracy. The RMSE values, falling within the 3-4% range, are considered acceptable due to their alignment with the total uncertainty inherent in spectrophotometer/spectroradiometer measurements [16,43]. Among the surfaces analyzed, the "Parking with cobblestones" area stands out for its remarkably low RMSE of 0.01.…”

“…The initial aim of the study was to compare all field measurements, along with satellite data, to laboratory measurements obtained using the Jasco V-670 UV-Vis-NIR spectrophotometer. This instrument was enhanced with an additional 150 mm integrating sphere (ILN 725 model), covering the spectral range from 300 nm to 2500 nm [16]. However, the instrument requires a sample of urban surfaces for analysis, which proved challenging to obtain for the types of surfaces under study.…”

“…These methods employ a range of instruments tailored to specific standards. Notable instruments include a spectrophotometer equipped with a 150 mm integrating sphere spanning wavelengths from 300 to 2500 nm, a reflectometer, and a pyranometer [16]. These instruments are detailed in ASTM standards such as ASTM E903, ASTM C1549, and ASTM E1918, respectively [17,18].…”

Bioinspired daytime radiative cooling performance: a new experimental protocol for scaling up passive cooling through the atmospheric windows

“…In this regard, the Solar Reflectance Index (SRI), developed by Akbari et al [4][5][6][7][8], offers a standardized metric for assessing the thermal behavior of surfaces under solar radiation. This metric has been widely adopted in rating systems and regulations, enabling fair product comparison and assessment of building performance.…”

Mensurando o índice de refletância solar para a superfície de solo

“…A medição da reflectância da superfície do solo, ou o Índice de Reflectância Solar, é uma técnica que tem sido utilizada para medir o albedo espectral dos solos (Costanzini, 2021). Existem muitas aplicações para este índice, uma delas é de quantificar os níveis de umidade do solo, dá a sua correlação com os coeficientes de absorção e espalhamento (Loshelder, 2020) e (Fabre, 2015).…”