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    ASTM E903 - 20

    Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres

    Active Standard ASTM E903 | Developed by Subcommittee: E44.20

    Book of Standards Volume: 12.02

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    Significance and Use

    5.1 Solar-energy absorptance, reflectance, and transmittance are important in the performance of all solar energy systems ranging from passive building systems to central receiver power systems. This test method provides a means for determining these values under fixed conditions that represent an average that would be encountered during use of a system in the temperate zone.

    5.2 Solar-energy absorptance, reflectance, and transmittance are important for thermal control of spacecraft and the solar power of extraterrestrial systems. This test method also provides a means for determining these values for extraterrestrial conditions.

    5.3 This test method is designed to provide reproducible data appropriate for comparison of results among laboratories or at different times by the same laboratory and for comparison of data obtained on different materials.

    5.4 This test method has been found practical for smooth materials having both specular and diffuse optical properties. Materials that are textured, inhomogeneous, patterned, or corrugated require special consideration.

    5.4.1 Surface roughness may be introduced by physical or chemical processes, such as pressing, rolling, etching, or deposition of films or chemical layers on materials, resulting in textured surfaces.

    5.4.2 The magnitude of surface roughness with respect to the components of the spectrophotometer and attachments (light beam sizes, sphere apertures, sample holder configuration) can significantly affect the accuracy of measurements using this test method.

    5.4.3 Even if the repeatability, or precision of the measurement of textured materials is good, including repeated measurements at various locations within or orientations of the sample, the different characteristics of different spectrophotometers in different laboratories may result in significant differences in measurement results.

    5.4.4 In the context of 5.4.3, the term ‘significant’ means differences exceeding the calibration or measurement uncertainty, or both, established for the spectrophotometers involved, through measurement of or calibration with standard reference materials.

    5.4.5 The caveats of 5.4.3 and 5.4.4 apply as well to measurement of smooth inhomogeneous or diffusing materials, where incident light may propogate to the edge of the test material and be ‘lost’ with respect to the measurement.

    5.5 This test method describes measurements accomplished over wider spectral ranges than the Photopic response of the human eye. Measurements are typically made indoors using light sources other than natural sunlight, though it is possible to configure systems using natural sunlight as the illumination source, as in Practice E424. Practice E971 describes outdoor methods using natural sunlight over the spectral response range of the human eye.

    5.6 Light diffracted by gratings is typically significantly polarized. For polarizing samples, measurement data will be a function of the orientation of the sample. Polarization effects may be detected by measuring the sample with rotation at various angles about the normal to the samples.

    1. Scope

    1.1 This test method covers the measurement of spectral absorptance, reflectance, and transmittance of materials using spectrophotometers equipped with integrating spheres.

    1.2 Methods of computing solar weighted properties from the measured spectral values are specified.

    1.3 This test method is applicable to materials having both specular and diffuse optical properties.

    1.4 This test method is applicable to material with applied optical coatings with special consideration for the impact on the textures of the material under test.

    1.5 Transmitting sheet materials that are inhomogeneous, textured, patterned, or corrugated require special considerations with respect to the applicability of this test method. Test Method E1084 may be more appropriate to determine the bulk optical properties of textured or inhomogeneous materials.

    1.6 For homogeneous materials this test method is preferred over Test Method E1084.

    1.7 This test method refers to applications using standard reference solar spectral distributions but may be applied using alternative selected spectra as long as the source and details of the solar spectral distribution and weighting are reported.

    1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

    1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    E275 Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers

    E424 Test Methods for Solar Energy Transmittance and Reflectance (Terrestrial) of Sheet Materials

    E490 Standard Solar Constant and Zero Air Mass Solar Spectral Irradiance Tables

    E772 Terminology of Solar Energy Conversion

    E971 Practice for Calculation of Photometric Transmittance and Reflectance of Materials to Solar Radiation

    E1084 Test Method for Solar Transmittance (Terrestrial) of Sheet Materials Using Sunlight

    E1175 Test Method for Determining Solar or Photopic Reflectance, Transmittance, and Absorptance of Materials Using a Large Diameter Integrating Sphere

    E2554 Practice for Estimating and Monitoring the Uncertainty of Test Results of a Test Method Using Control Chart Techniques

    G173 Tables for Reference Solar Spectral Irradiances: Direct Normal and Hemispherical on 37 Tilted Surface

    G197 Table for Reference Solar Spectral Distributions: Direct and Diffuse on 20 Tilted and Vertical Surfaces

    Other Documents

    ASHRAE Standard 74-1988 Available from American Society of Heating, Refrigeration, and Air-Conditioning Engineers, Inc., 191 Tullie Circle, NE. Atlanta GA 30329.

    CIE 38 Radiometric and Photometric Characteristics of Materials and their Measurement Available from U.S. National Committee of the CIE (International Commission on Illumination), C/o Thomas M. Lemons, TLA-Lighting Consultants, Inc., 7 Pond St., Salem, MA 01970, http://www.cie-usnc.org.

    Federal Test Method Standard No. 141, Method 6101 Available from Standardization Documents, Order Desk, Building 4, Section D, 700 Robbins Ave., Philadelphia, PA 19111-5049, Attn: NPODS.

    NIST SP 250-48 Spectral Reflectance Online, Available: https://www.nist.gov/publications/spectral-reflectance

    ICS Code

    ICS Number Code 77.140.80 (Iron and steel castings)

    UNSPSC Code

    UNSPSC Code

    Referencing This Standard
    Link Here
    Link to Active (This link will always route to the current Active version of the standard.)

    DOI: 10.1520/E0903-20

    Citation Format

    ASTM E903-20, Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres, ASTM International, West Conshohocken, PA, 2020, www.astm.org

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