1、Designation: G 173 03e1Standard Tables forReference Solar Spectral Irradiances: Direct Normal andHemispherical on 37 Tilted Surface1This standard is issued under the fixed designation G 173; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEThe reference to ADJG0173CD was added editorially in March 2006.INTRODUCTIONA wide variety of solar spe
3、ctral energy distributions occur in the natural environment and aresimulated by artificial sources during product, material, or component testing. To compare the relativeoptical performance of spectrally sensitive products a reference standard solar spectral distribution isrequired. These tables rep
4、lace ASTM standard G 159, which has been withdrawn. The solar spectralenergy distribution presented in this standard are not intended as a benchmark for ultraviolet radiationin weathering exposure testing of materials. The spectra are based on version 2.9.2 of the SimpleModel of the Atmospheric Radi
5、ative Transfer of Sunshine (SMARTS) atmospheric transmission code(1,2).2SMARTS uses empirical parameterizations of version 4.0 of the Air Force GeophysicalLaboratory (AFGL) Moderate Resolution Transmission model, MODTRAN (3,4) for some gaseousabsorption processes, and recent spectroscopic data for o
6、thers. An extraterrestrial spectrum differingonly slightly from the extraterrestrial spectrum in ASTM E 490 is used to calculate the resultantspectra (5). The hemispherical tilted spectrum is similar to the hemispherical spectrum in use since1987, but differs from it because: (1) the wavelength rang
7、e for the current spectrum has been extendeddeeper into the ultraviolet; (2) uniform wavelength intervals are now used; (3) more representativeatmospheric conditions are represented,; and (4) SMARTS Version 2.9.2 has been used as thegenerating model. For the same reasons, and particularly the adopti
8、on of a remarkably less turbidatmosphere than before, significant differences exist in the reference direct normal spectrum comparedto previous versions of this standard. The input parameters used in conjunction with SMARTS for theselected atmospheric conditions are tabulated. The SMARTS model and d
9、ocumentation are availableas an adjunct (ADJG01733) to this standard.1. Scope1.1 These tables contain terrestrial solar spectral irradiancedistributions for use in terrestrial applications that require astandard reference spectral irradiance for hemispherical solarirradiance (consisting of both dire
10、ct and diffuse components)incident on a sun-facing, 37 tilted surface or the direct normalspectral irradiance. The data contained in these tables reflectreference spectra with uniform wavelength interval (0.5 na-nometer (nm) below 400 nm, 1 nm between 400 and 1700 nm,an intermediate wavelength at 17
11、02 nm, and 5 nm intervalsfrom 1705 to 4000 nm). The data tables represent reasonablecloudless atmospheric conditions favorable for photovoltaic(PV) energy production, as well as weathering and durabilityexposure applications.1.2 The 37 slope of the sun-facing tilted surface waschosen to represent th
12、e average latitude of the 48 contiguousUnited States. A wide variety of orientations is possible forexposed surfaces. The availability of the SMARTS model (asan adjunct, ADJG0173CD3) to this standard) used to generatethe standard spectra allows users to evaluate differencesrelative to the surface sp
13、ecified here.1.3 The air mass and atmospheric extinction parameters arechosen to provide (1) historical continuity with respect toprevious standard spectra, (2) reasonable cloudless atmo-spheric conditions favorable for photovoltaic (PV) energyproduction or weathering and durability exposure, based
14、uponmodern broadband solar radiation data, atmospheric profiles,and improved knowledge of aerosol optical depth profiles. In1These tables are under the jurisdiction ofASTM Committee G03 onWeatheringand Durability and is the direct responsibility of Subcommittee G03.09 onRadiometry.Current edition ap
15、proved Jan. 10, 2003. Published April 2003.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3Available from ASTM International Headquarters. Order Adjunct No.ADJG0173CD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken
16、, PA 19428-2959, United States.nature, an extremely large range of atmospheric conditions canbe encountered even under cloudless skies. Considerabledeparture from the reference spectra may be observed depend-ing on time of day, geographical location, and changingatmospheric conditions. The availabil
17、ity of the SMARTSmodel (as an adjunct (ADJG0173CD3)to this standard) used togenerate the standard spectra allows users to evaluate spectraldifferences relative to the spectra specified here.2. Referenced Documents2.1 ASTM Standards:4E 490 Standard Solar Constant and Zero Air Mass SolarSpectral Irrad
18、iance TablesE 772 Terminology Relating to Solar Energy ConversionG 113 Terminology Relating to Natural and ArtificialWeathering Tests of Nonmetallic Materials2.2 ASTM Adjunct:3ADJG0173CD Simple Model for Atmospheric Transmis-sion of Sunshine3. Terminology3.1 DefinitionsDefinitions of most terms used
19、 in thisspecification may be found in Terminology E 772.3.2 The following definition differs from that in Terminol-ogy E 772, representing information current as of this revision.3.2.1 solar constantthe total solar irradiance at normalincidence on a surface in free space at the earths meandistance f
20、rom the sun. (1 astronomical unit, or AU = 1.496 31011m).3.2.1.1 DiscussionThe solar constant is now knownwithin about 61.5 Wm-2. Its current accepted values are1366.1 Wm-2(ASTM E 490) or 1367.0 Wm-2(World Meteo-rological Organization, WMO), and are subject to change. Dueto the eccentricity of the e
21、arths orbit, the actual extraterrestrialsolar irradiance varies by 63.4 % about the solar constant asthe earth-sun distance varies through the year. Throughout thisstandard the solar constant is defined as 1367.0 Wm-2.3.3 Definitions of Terms Specific to This Standard:3.3.1 aerosol optical depth (AO
22、D)the wavelength-dependent total extinction (scattering and absorption) by aero-sols in the atmosphere. This optical depth (also called “opticalthickness”) is defined here at 500 nm.3.3.1.1 DiscussionSee Appendix X1.3.3.2 air mass zero (AM0)describes solar radiation quan-tities outside the Earths at
23、mosphere at the mean Earth-Sundistance (1 Astronomical Unit). See ASTM E 490.3.3.3 integrated irradiance El1-l2spectral irradiance inte-grated over a specific wavelength interval from l1to l2,measured in Wm-2; mathematically:El12l25*l1l2Eldl (1)3.3.4 solar irradiance, hemispherical EHon a given plan
24、e,the solar radiant flux received from within the 2p steradianfield of view of a tilted plane from the portion of the sky domeand the foreground included in the planes field of view,including both diffuse and direct solar radiation.3.3.4.1 DiscussionFor the special condition of a horizon-tal plane t
25、he hemispherical solar irradiance is properly termedglobal solar irradiance, EG. Incorrectly, global tilted, or totalglobal irradiance is often used to indicate hemisphericalirradiance for a tilted plane. In case of a sun-tracking receiver,this hemispherical irradiance is commonly called global nor-
26、mal irradiance. The adjective global should refer only tohemispherical solar radiation on a horizontal, not a tilted,surface.3.3.5 solar irradiance, spectral Elsolar irradiance E perunit wavelength interval at a given wavelength l (unit: Wattsper square meter per nanometer, Wm-2nm-1):El5dEdl(2)3.3.6
27、 spectral intervalthe distance in wavelength unitsbetween adjacent spectral irradiance data points.3.3.7 spectral passbandthe effective wavelength intervalwithin which spectral irradiance is allowed to pass, as througha filter or monochromator. The convolution integral of thespectral passband (norma
28、lized to unity at maximum) and theincident spectral irradiance produces the effective transmittedirradiance.3.3.7.1 DiscussionSpectral passband may also be referredto as the spectral bandwidth of a filter or device. Passbands areusually specified as the interval between wavelengths at whichone half
29、of the maximum transmission of the filter or deviceoccurs, or as full-width at half-maximum, FWHM.3.3.8 spectral resolutionthe minimum wavelength differ-ence between two wavelengths that can be identified unam-biguously.3.3.8.1 DiscussionIn the context of this standard, thespectral resolution is sim
30、ply the interval, Dl, between spectraldata points, or the spectral interval.3.3.9 total ozonethe depth of a column of pure ozoneequivalent to the total of the ozone in a vertical column fromthe ground to the top of the atmosphere (unit: atmosphere-cmor atm-cm).3.3.10 total precipitable waterthe dept
31、h of a column ofwater (with a section of 1 cm2) equivalent to the condensedwater vapor in a vertical column from the ground to the top ofthe atmosphere (unit: cm or g/cm2).3.3.11 wavenumbera unit of frequency, n, in units ofreciprocal centimeters (symbol cm-1) commonly used in placeof wavelength, l
32、(units of length, typically nanometers). Toconvert wavenumber to nanometers, l nm=1107/ n cm-1.See X1.2.4. Significance and Use4.1 Absorptance, reflectance, and transmittance of solarenergy are important factors in material degradation studies,solar thermal system performance, solar photovoltaic sys
33、temperformance, biological studies, and solar simulation activities.These optical properties are normally functions of wavelength,which require the spectral distribution of the solar flux beknown before the solar-weighted property can be calculated.4For referenced ASTM standards, visit the ASTM webs
34、ite, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.G17303e12To compare the relative performance of competitive products,or to compare the performance of products b
35、efore and afterbeing subjected to weathering or other exposure conditions, areference standard solar spectral distribution is desirable.4.2 These tables provide appropriate standard spectral irra-diance distributions for determining the relative optical perfor-mance of materials, solar thermal, sola
36、r photovoltaic, and othersystems. The tables may be used to evaluate components andmaterials for the purpose of solar simulation where either thedirect or the hemispherical (that is, direct beam plus diffusesky) spectral solar irradiance is desired. However, these tablesare not intended to be used a
37、s a benchmark for ultravioletradiation used in indoor exposure testing of materials usingmanufactured light sources.4.3 The total integrated irradiances for the direct and hemi-spherical tilted spectra are 900.1 Wm-2and 1000.4 Wm-2,respectively. Note that, in PV applications, no amplitudeadjustments
38、 are required to match standard reporting conditionirradiances of 1000 Wm-2for hemispherical irradiance.4.4 Previously defined global hemispherical reference spec-trum (G 159) for a sun-facing 37-tilted surface served well tomeet the needs of the flat plate photovoltaic research, devel-opment, and i
39、ndustrial community. Investigation of prevailingconditions and measured spectra shows that this global hemi-spherical reference spectrum can be attained in practice undera variety of conditions, and that these conditions can beinterpreted as representative for many combinations of atmo-spheric param
40、eters. Earlier global hemispherical referencespectrum may be closely, but not exactly, reproduced withimproved spectral wavelength range, uniform spectral interval,and spectral resolution equivalent to the spectral interval, usinginputs in X1.4.4.5 Reference spectra generated by the SMARTS Version2.
41、9.2 model for the indicated conditions are shown in Fig. 1.The exact input file structure required to generate the referencespectra is shown in Table 1.4.6 The availability of the adjunct (ADJG0173CD3) stan-dard computer software for SMARTS allows one to (1)reproduce the reference spectra, using the
42、 above input param-eters; (2) compute test spectra to attempt to match measureddata at a specified FWHM, and evaluate atmospheric condi-tions; and (3) compute test spectra representing specific con-ditions for analysis vis-vis any one or all of the referencespectra.4.7 Differences from the previous
43、standard spectra (G 159)can be summarized as follows:4.7.1 Extended spectral interval in the ultraviolet (down to280 nm, rather than 305 nm),4.7.2 Better resolution (2002 wavelengths, as compared to120),4.7.3 Constant intervals (0.5 nm below 400 nm, 1 nmbetween 400 and 1700 nm, and 5 nm above),4.7.4
44、 Better definition of atmospheric scattering and gas-eous absorption, with more species considered,4.7.5 Better defined extraterrestrial spectrum,4.7.6 More realistic spectral ground reflectance, and4.7.7 Lower aerosol optical depth, yielding significantlylarger direct normal irradiance.FIG. 1 Plot
45、of Direct Normal Spectral Irradiance (Solid Line) and Hemispherical Spectral Irradiance on 37 Tilted Sun-Facing Surface(Dotted Line) Computed Using Smarts Version 2.9.2 Model With Input File in Table 1G17303e135. Technical Bases for the Tables5.1 These tables are modeled data generated using an airm
46、ass zero (AM0) spectrum based in part on the extraterrestrialspectrum of Kurucz (5), the 1976 U.S. Standard Atmosphere(6), the Shettle and Fenn Rural Aerosol Profile (7), theSMARTS radiative transfer code, version 2.9.2, and associatedinput data files.5.2 In order to provide spectral data with a uni
47、form spectralstep size and improved spectral resolution, the AM0 spectrumused in conjunction with SMARTS to generate the terrestrialspectrum is slightly different from the ASTM extraterrestrialspectrum, ASTM E 490. Because ASTM E 490 and SMARTSboth use the Kurucz data, the SMARTS and E 490 spectra a
48、rein good agreement though they do not have the same spectralinterval step sizes, spectral interval centers, or spectral resolu-tion.5.3 The 1976 U.S. Standard Atmosphere (USSA) is used toprovide documented atmospheric properties and concentra-tions of absorbers. However, some newly documented (andr
49、elatively minor) absorbers are taken into consideration in thepresent standard spectra. See X1.3.5.4 The SMARTS model code and documentation is avail-able from the NREL(National Renewable Energy Lab) website(www.nrel.gov).5.5 These terrestrial solar spectral data are based on thework of Gueymard (1,2) and Gueymard et al. (8). Previouslydefined reference spectra were based on the work of Bird,Hulstrom, and Lewis (9). The current spectra reflect current (asof 2002) improved knowledge of gaseous absorption, atmo-spheric aerosol optical properties,
