1、Designation: C1549 09Standard Test Method forDetermination of Solar Reflectance Near AmbientTemperature Using a Portable Solar Reflectometer1This standard is issued under the fixed designation C1549; the number immediately following the designation indicates the year oforiginal adoption or, in the c
2、ase of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a technique for determining thesolar reflectance of flat opaque m
3、aterials in a laboratory or inthe field using a commercial portable solar reflectometer. Thepurpose of the test method is to provide solar reflectance datarequired to evaluate temperatures and heat flows across sur-faces exposed to solar radiation.1.2 This test method does not supplant Test Method E
4、903which measures solar reflectance over the wavelength range250 to 2500 nm using integrating spheres. The portable solarreflectometer is calibrated using specimens of known solarreflectance to determine solar reflectance from measurementsat four wavelengths in the solar spectrum: 380 nm, 500 nm,650
5、 nm, and 1220 nm. This technique is supported bycomparison of reflectometer measurements with measurementsobtained using Test Method E903. This test method is appli-cable to specimens of materials having both specular anddiffuse optical properties. It is particularly suited to themeasurement of the
6、solar reflectance of opaque materials.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the u
7、ser of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents22.1 ASTM Standards:C168 Terminology Relating to Thermal InsulationE691 Practice for Conducting an Interlaboratory Study toDetermi
8、ne the Precision of a Test MethodE903 Test Method for Solar Absorptance, Reflectance, andTransmittance of Materials Using Integrating Spheres3E1980 Practice for Calculating Solar Reflectance Index ofHorizontal and Low-Sloped Opaque Surfaces2.2 Additional Reference:“Instructions for the Solar Spectru
9、m Reflectometer ModelSSR-ER,” Devices and Services Company43. Terminology3.1 DefinitionsFor definitions of some terms used in thetest method, refer to Terminology C168.3.2 Definitions of Terms Specific to This Standard:3.2.1 air massair mass is related to the path length ofsolar radiation through th
10、e Earths atmosphere to the site ofinterest.Air mass 1 is for a path of normal solar radiation at theEarths equator while air mass 2 indicates two times this pathlength.3.2.2 solar reflectancethe fraction of incident solar radia-tion upon a surface that is reflected from the surface.3.3 Symbols:A = a
11、rea normal to incident radiation, m2Qabs= rate at which radiant heat is absorbed per m2ofarea, Wqsolar= solar flux, W/m2r = solar reflectance, dimensionless4. Summary of Test Method4.1 This test method employs a diffuse tungsten halogenlamp to illuminate a flat specimen for two seconds out of aten-s
12、econd measurement cycle. Reflected light is measured atan angle of 20 from the incident angle with four detectors.Each detector is equipped with color filters to tailor itselectrical response to a range of wavelengths in the solarspectrum. Software in the instrument combines the outputs ofthe four d
13、etectors in appropriate proportions to approximate theresponse for incident solar radiation through air mass 0, 1, 1.5,1This test method is under the jurisdiction ofASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.30 on ThermalMeasurement.Current edition a
14、pproved Nov. 1, 2009. Published January 2010. Originallyapproved in 2002. Last previous edition approved in 2002 as C1549 02. DOI:10.1520/C1549-09.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandard
15、s volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.4The sole source of supply of the apparatus known to the committee at this timeis Devices reflectometer; solar reflecta
16、nce;solar reflectometerTABLE 1 Solar Reflectances (%) of Roofing MaterialsPrecisionStatisticsMaterial Average SrSRrRA 5.79 0.10 0.15 0.29 0.43B 13.85 0.06 0.17 0.17 0.48C 28.93 0.17 0.72 0.47 2.01D 35.57 0.15 0.23 0.41 0.65E 49.53 0.12 0.46 0.34 1.27F 76.00 0.14 0.51 0.38 1.42G 84.69 0.21 0.43 0.59
17、1.21TABLE 2 Bias of Test Method C1549 for Solar Reflectance fromTest Method E903Material E903 C1549 C1549 E903A 6.0 5.8 -0.2B 13.0 13.9 0.9C 26.0 28.9 2.9D 34.0 35.6 1.6E 47.0 49.5 2.5F 74.0 76.0 2.0G 83.0 84.7 1.7C1549 093APPENDIX(Nonmandatory Information)X1. TECHNIQUE FOR MEASURING SOLAR REFLECTAN
18、CE OF A FLAT, OPAQUE, AND HETEROGENEOUS SURFACEUSING A PORTABLE SOLAR REFLECTORX1.1 ScopeThis is a technique for measuring the meansolar reflectance of a flat, opaque, and heterogeneous surfacesuch as a variegated, granule-covered asphalt roofing shingle atstandard conditions. The mean solar reflect
19、ance of the surfaceis determined by averaging the solar reflectances of spots(small regions) measured with a commercial portable solarreflectometer built and operated in accordance with ASTMC1549. This technique does not purport to address all of thesafety concerns, if any, associated with its use.
20、It is theresponsibility of the user to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use. The results obtained using this appen-dix apply only to the material tested.X1.2 TerminologyX1.2.1 estimate of sample mean standard errorthes
21、ample standard deviation divided by the square root of thenumber of elements in the sample.X1.2.2 heterogeneousconsisting of dissimilar or diverseingredients or constituents.X1.2.3 populationthe set of values about which conclu-sions are to be drawn, such as a set of solar reflectance valuesdetermin
22、ed from non-overlapping spots that cover an entire testsurface.X1.2.4 population meanthe arithmetic mean of the prop-erty values (that is, solar reflectances) measured for all mem-bers of a population.X1.2.5 population standard deviationthe square root ofthe arithmetic mean of the squares of the dev
23、iation from thepopulation mean.X1.2.6 reflectometera device that measures reflectance.X1.2.7 sample meanthe arithmetic mean of the propertyvalues (that is, solar reflectances) measured for all members ofa sample set.X1.2.8 sample mean standard errorthe population stan-dard deviation divided by the s
24、quare root of the number ofsamples.X1.2.9 sample seta subset of the population, such as a setof non-overlapping spots on a test surface.X1.2.10 sample standard deviationthe square root of theratio of the sum of the squares of the deviation from the samplemean to a number one less than the number of
25、samples.X1.2.11 spota small region of a test surface, such as a 25by 25 mm square or a 25 mm diameter circle.X1.2.12 test surfacea flat, opaque, and heterogeneoussurface, for example, a variegated, granule-covered asphaltshingle.X1.2.13 test surface mean solar reflectancethe ratio ofsolar energy ref
26、lected from a test surface to the solar energyincident on a test surface (equal to the ratio of area-integratedsolar reflectance to area).X1.2.14 variegatedhaving discrete markings of differentcolors.X1.3 Summary of TechniqueX1.3.1 For a flat, opaque, and heterogeneous test surface,solar reflectance
27、s shall be measured in accordance with TestMethod C1549 at a series of randomly located, non-overlapping spots until the sample mean standard error is smallenough to use the sample mean as an estimate of the mean solarreflectance of the test surface. An algorithm for selectingmeasurement locations,
28、computing the sample mean, andcomputing the sample mean standard error is available fromthe Cool Roof Rating Council (CRRC).6X1.4 Significance and UseX1.4.1 This technique provides a method for determiningthe mean solar reflectance of a flat, opaque, and heterogeneoussurface, from multiple, random a
29、nd non-duplicative spot mea-surements of solar reflectance.X1.5 ProcedureX1.5.1 Set-up:X1.5.1.1 Obtain a representative test specimen, as definedby CRRC 1.6X1.5.1.2 Let w and h represent the width and height of thetest surface in mm.X1.5.1.3 Place a pair of rulers at a right angle on two sidesof the
30、 test Surface to establish a grid of square cells, each 25 by25 mm and centered on integer coordinates. (A ruler marked ininches is convenient for this step.) If the area of the test surfacedoes not exceed 0.019 m2, then apply Procedure A. If the areais 0.019 m2or greater, then apply Procedure B.X1.
31、5.1.4 Procedure A:(1) Measure the solar reflectance at the center of each cellwith a solar spectrum reflectometer in accordance with TestMethod C1549, centered over each cell.(2) Report the mean value of cell solar reflectance as themean solar reflectance of the test surface.X1.5.1.5 Procedure B:(1)
32、 Measure the solar reflectances at the centers of aminimum of 30 different and randomly selected cells inaccordance with Test Method C1549.(2) Compute the mean, standard deviation, and estimate ofstandard error of the solar reflectance of the sample set. Thesequantities are defined in Equations in X
33、1.5.2.6Available from Cool Roof Rating Council (CRRC)1610 Harrison StreetOakland, CA 94612. http:/www.coolroofs.orgC1549 094(3) If the estimate of sample mean standard error exceeds0.005, increase the number of samples by measuring solarreflectances of additional, different, and randomly selectedcel
34、ls(4) Repeat (2) and (3) until the estimate of sample meanstandard error of the sample set does not exceed 0.005.(5) Report the sample mean plus or minus twice theestimate of sample mean standard error as the mean solarreflectance to within 95% confidence.X1.5.2 Calculations:X1.5.2.1 All reflectance
35、s in the following discussion aresolar reflectances.The mean reflectance:r A21*ArdA (X1.1)of a test surface of area is equal to the mean reflectance of theentire population of surface “spots,”1n(i51nri(X1.2)Each spot is a region of reflectance and area that is smallenough to be measured with the ref
36、lectometer, and does notoverlap any of its neighbors. If is large, it is convenient toestimate the population mean spot reflectance , and hence thetest surface mean reflectance , of a large surface by randomlysampling a population subset. Consider a sample set ofdifferent, non-overlapping, and rando
37、mly located spots thathave mean reflectance:r1n(i51nri(X1.3)with standard deviation:s1n(i51n ri rn!2(X1.4)By the Central Limit theorem, the sample mean has a standarderror:sr5s/=n (X1.5)where s is the standard deviation of the spot reflectances of theentire population (Crow et al., 1960). The popula
38、tion meanspot reflectance (which is also the mean solar reflectance of thetest surface,) is equal to (95% confidence). If the sample size nis sufficiently large (say, n $ 30), then the population standarddeviation s is well approximated by the sample standarddeviation s , and the estimate of the sam
39、ple mean standard errorissr s=n (X1.6)The instrument used to measure spot reflectance in accordancewith Test Method C1549 has a circular aperture. Hence, the testsurface formed by a matrix of contiguous, non-overlappingcircular measurement spots will cover a fraction p/4 0.79 ofthe rectangular regio
40、n bounding the matrix of circles. Theremaining 21% of the rectangular region will not be sampled.This should be acceptable if the optical properties of the areabetween each measurement circle and its bounding square areexpected to be the same as those of the surface within eachmeasurement circle.X1.
41、6 ReportX1.6.1 Include the following in the report in addition to therequirements stated in Test Method C1549.(1) The width, length, and area of the test surface,(2) The solar reflectance measurement procedure followed(A or B),(3) The central coordinates and solar reflectance of eachcell measured,(4
42、) For Procedure A, the mean solar reflectance of the testsurface, equal to the mean value of cell solar reflectance,(5) For Procedure B (applied to test surfaces exceeding0.019 m2, the mean solar reflectance of the test surface towithin 95% confidence, expressed as the sample mean plus orminus two t
43、imes the estimate of sample mean standard error,(6) Manufacturer of the product,(7) Manufacturer-designated product name and color, and(8) Date specimen was tested.X1.7 Precision and BiasX1.7.1 BiasNo statement concerning bias is made sincethere is no standard reference material for solar reflectanc
44、e.X1.7.2 Procedure B was evaluated in a round robin involv-ing five laboratories and six products. A precision statementbased on E691 is shown in Table X1.1. Precision characterizedby the reproducibility standard deviations, SR, and the 95%reproducibility limits R have been determined. R values were
45、calculated using 2.8 times SR. Data needed for repeatabilitywere not obtained.X1.7.3 PrecisionThis precision statement is provisionalsince the data obtained do not meet the minimum requirementsof E691.TABLE X1.1 Solar Reflectance (%) for Six MaterialsMaterial Average Solar Reflectance SRR1 6.06 0.57
46、 1.592 3.76 0.26 0.733 19.10 1.09 3.044 6.90 0.33 0.935 6.14 0.34 0.966 5.66 0.47 1.30C1549 095ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determina
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