ASTM G173-03(2008)
(Guide)Standard Tables for Reference Solar Spectral Irradiances: Direct Normal and Hemispherical on 37° Tilted Surface
Standard Tables for Reference Solar Spectral Irradiances: Direct Normal and Hemispherical on 37° Tilted Surface
SIGNIFICANCE AND USE
Absorptance, reflectance, and transmittance of solar energy are important factors in material degradation studies, solar thermal system performance, solar photovoltaic system performance, biological studies, and solar simulation activities. These optical properties are normally functions of wavelength, which require the spectral distribution of the solar flux be known before the solar-weighted property can be calculated. To compare the relative performance of competitive products, or to compare the performance of products before and after being subjected to weathering or other exposure conditions, a reference standard solar spectral distribution is desirable.
These tables provide appropriate standard spectral irradiance distributions for determining the relative optical performance of materials, solar thermal, solar photovoltaic, and other systems. The tables may be used to evaluate components and materials for the purpose of solar simulation where either the direct or the hemispherical (that is, direct beam plus diffuse sky) spectral solar irradiance is desired. However, these tables are not intended to be used as a benchmark for ultraviolet radiation used in indoor exposure testing of materials using manufactured light sources.
The total integrated irradiances for the direct and hemispherical tilted spectra are 900.1 W·m-2 and 1000.4 W·m-2, respectively. Note that, in PV applications, no amplitude adjustments are required to match standard reporting condition irradiances of 1000 W·m-2 for hemispherical irradiance.
Previously defined global hemispherical reference spectrum (G159) for a sun-facing 37°-tilted surface served well to meet the needs of the flat plate photovoltaic research, development, and industrial community. Investigation of prevailing conditions and measured spectra shows that this global hemispherical reference spectrum can be attained in practice under a variety of conditions, and that these conditions can be interpreted as representative fo...
SCOPE
1.1 These tables contain terrestrial solar spectral irradiance distributions for use in terrestrial applications that require a standard reference spectral irradiance for hemispherical solar irradiance (consisting of both direct and diffuse components) incident on a sun-facing, 37° tilted surface or the direct normal spectral irradiance. The data contained in these tables reflect reference spectra with uniform wavelength interval (0.5 nanometer (nm) below 400 nm, 1 nm between 400 and 1700 nm, an intermediate wavelength at 1702 nm, and 5 nm intervals from 1705 to 4000 nm). The data tables represent reasonable cloudless atmospheric conditions favorable for photovoltaic (PV) energy production, as well as weathering and durability exposure applications.
1.2 The 37° slope of the sun-facing tilted surface was chosen to represent the average latitude of the 48 contiguous United States. A wide variety of orientations is possible for exposed surfaces. The availability of the SMARTS model (as an adjunct, ADJG173CD ) to this standard) used to generate the standard spectra allows users to evaluate differences relative to the surface specified here.
1.3 The air mass and atmospheric extinction parameters are chosen to provide (1) historical continuity with respect to previous standard spectra, (2) reasonable cloudless atmospheric conditions favorable for photovoltaic (PV) energy production or weathering and durability exposure, based upon modern broadband solar radiation data, atmospheric profiles, and improved knowledge of aerosol optical depth profiles. In nature, an extremely large range of atmospheric conditions can be encountered even under cloudless skies. Considerable departure from the reference spectra may be observed depending on time of day, geographical location, and changing atmospheric conditions. The availability of the SMARTS model (as an adjunct (ADJG173CD )to this standard) used to generate the standard spectra a...
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: G173 − 03 (Reapproved2008)
Standard Tables for
Reference Solar Spectral Irradiances: Direct Normal and
1
Hemispherical on 37° Tilted Surface
This standard is issued under the fixed designation G173; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
A wide variety of solar spectral energy distributions occur in the natural environment and are
simulatedbyartificialsourcesduringproduct,material,orcomponenttesting.Tocomparetherelative
optical performance of spectrally sensitive products a reference standard solar spectral distribution is
required. These tables replace ASTM standard G159, which has been withdrawn. The solar spectral
energydistributionpresentedinthisstandardarenotintendedasabenchmarkforultravioletradiation
in weathering exposure testing of materials. The spectra are based on version 2.9.2 of the Simple
Model of theAtmospheric RadiativeTransfer of Sunshine (SMARTS) atmospheric transmission code
2
(1,2). SMARTS uses empirical parameterizations of version 4.0 of the Air Force Geophysical
Laboratory (AFGL) Moderate Resolution Transmission model, MODTRAN (3,4) for some gaseous
absorption processes, and recent spectroscopic data for others. An extraterrestrial spectrum differing
onlyslightlyfromtheextraterrestrialspectruminTablesE490isusedtocalculatetheresultantspectra
(5).The hemispherical tilted spectrum is similar to the hemispherical spectrum in use since 1987, but
differs from it because: (1) the wavelength range for the current spectrum has been extended deeper
into the ultraviolet; (2) uniform wavelength intervals are now used; (3) more representative
atmospheric conditions are represented,; and (4) SMARTS Version 2.9.2 has been used as the
generating model. For the same reasons, and particularly the adoption of a remarkably less turbid
atmospherethanbefore,significantdifferencesexistinthereferencedirectnormalspectrumcompared
to previous versions of this standard.The input parameters used in conjunction with SMARTS for the
selected atmospheric conditions are tabulated. The SMARTS model and documentation are available
3
as an adjunct (ADJG173CD ) to this standard.
1. Scope 1705 to 4000 nm). The data tables represent reasonable
cloudless atmospheric conditions favorable for photovoltaic
1.1 These tables contain terrestrial solar spectral irradiance
(PV) energy production, as well as weathering and durability
distributions for use in terrestrial applications that require a
exposure applications.
standard reference spectral irradiance for hemispherical solar
irradiance (consisting of both direct and diffuse components)
1.2 The 37° slope of the sun-facing tilted surface was
incidentonasun-facing,37°tiltedsurfaceorthedirectnormal
chosen to represent the average latitude of the 48 contiguous
spectral irradiance. The data contained in these tables reflect
United States. A wide variety of orientations is possible for
reference spectra with uniform wavelength interval (0.5 nano-
exposed surfaces. The availability of the SMARTS model (as
3
meter(nm)below400nm,1nmbetween400and1700nm,an
an adjunct, ADJG173CD ) to this standard) used to generate
intermediate wavelength at 1702 nm, and 5 nm intervals from
the standard spectra allows users to evaluate differences
relative to the surface specified here.
1
ThesetablesareunderthejurisdictionofASTMCommitteeG03onWeathering
1.3 The air mass and atmospheric extinction parameters are
and Durability and is the direct responsibility of Subcommittee G03.09 on
chosen to provide (1) historical continuity with respect to
Radiometry.
previous standard spectra, (2) reasonable cloudless atmo-
Current edition approved June 1, 2008. Published October 2008. Originally
´1
spheric conditions favorable for photovoltaic (PV) energy
approved in 2003. Last previous edition approved in 2003 as G173–03 . DOI:
10.1520/G0173-03R08.
production or weathering and durability exposure, based upon
2
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
modern broadband solar radiation data, atmospheric profiles,
this standard.
3
and improved knowledge of aerosol optical depth profiles. In
Available from ASTM International Headquarters. Order Adjunct No.
ADJG173CD. Original adjunct produced in 2005. nature,anextremelylargerangeofatmosphericconditionscan
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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G173 − 03 (2008)
be encountered even under cloudless skies. Considerable and the foreground included in the plane’s field of view,
depart
...
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