ASTM E772-15(2021)
(Terminology)Standard Terminology of Solar Energy Conversion
Standard Terminology of Solar Energy Conversion
SCOPE
1.1 This terminology pertains to the conversion of solar energy into other forms of energy by various means, including thermal absorption (i.e., solar thermal) and the photovoltaic effect (i.e., photovoltaics).
1.2 This terminology also pertains to instrumentation used to measure solar radiation.
1.3 This terminology also pertains to glass for solar energy applications.
1.4 Fundamental terms associated with electromagnetic radiation that are indicates as derived units in Standard IEEE/ASTM SI 10 are not repeated in this terminology.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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.
General Information
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Standards Content (Sample)
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.
Designation: E772 − 15 (Reapproved 2021)
Standard Terminology of
Solar Energy Conversion
This standard is issued under the fixed designation E772; 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.
1. Scope by Chemical Microscopy
D4865Guide for Generation and Dissipation of Static Elec-
1.1 This terminology pertains to the conversion of solar
tricity in Petroleum Fuel Systems
energy into other forms of energy by various means, including
D5544Test Method for On-Line Measurement of Residue
thermal absorption (i.e., solar thermal) and the photovoltaic
After Evaporation of High-Purity Water
effect (i.e., photovoltaics).
D7236Test Method for Flash Point by Small Scale Closed
1.2 This terminology also pertains to instrumentation used
Cup Tester (Ramp Method)
to measure solar radiation.
E349Terminology Relating to Space Simulation
1.3 This terminology also pertains to glass for solar energy
E490Standard Solar Constant and Zero Air Mass Solar
applications.
Spectral Irradiance Tables
1.4 Fundamental terms associated with electromagnetic ra- E491Practice for Solar Simulation for Thermal Balance
diation that are indicates as derived units in Standard IEEE/ Testing of Spacecraft
ASTM SI 10 are not repeated in this terminology.
E927Classification for Solar Simulators for Electrical Per-
formance Testing of Photovoltaic Devices
1.5 The values stated in SI units are to be regarded as
E948Test Method for Electrical Performance of Photovol-
standard. No other units of measurement are included in this
taic Cells Using Reference Cells Under Simulated Sun-
standard.
light
1.6 This international standard was developed in accor-
E816Test Method for Calibration of Pyrheliometers by
dance with internationally recognized principles on standard-
Comparison to Reference Pyrheliometers
ization established in the Decision on Principles for the
E1021TestMethodforSpectralResponsivityMeasurements
Development of International Standards, Guides and Recom-
of Photovoltaic Devices
mendations issued by the World Trade Organization Technical
E1036Test Methods for Electrical Performance of Noncon-
Barriers to Trade (TBT) Committee.
centrator Terrestrial Photovoltaic Modules and Arrays
Using Reference Cells
2. Referenced Documents
E1125 Test Method for Calibration of Primary Non-
2.1 ASTM Standards:
Concentrator Terrestrial Photovoltaic Reference Cells Us-
C162Terminology of Glass and Glass Products
ing a Tabular Spectrum
C1048Specification for Heat-Strengthened and Fully Tem-
E1171Test Methods for Photovoltaic Modules in Cyclic
pered Flat Glass
Temperature and Humidity Environments
C1651Test Method for Measurement of Roll Wave Optical
E1362Test Methods for Calibration of Non-Concentrator
Distortion in Heat-Treated Flat Glass
Photovoltaic Non-Primary Reference Cells
D1003Test Method for Haze and Luminous Transmittance
E1462Test Methods for Insulation Integrity and Ground
of Transparent Plastics
Path Continuity of Photovoltaic Modules
D1245Practice for Examination of Water-Formed Deposits
E2236Test Methods for Measurement of Electrical Perfor-
mance and Spectral Response of Nonconcentrator Multi-
junction Photovoltaic Cells and Modules
This terminology is under the jurisdiction ofASTM Committee E44 on Solar,
GeothermalandOtherAlternativeEnergySourcesandisthedirectresponsibilityof
E2527Test Method for Electrical Performance of Concen-
Subcommittee E44.01 on Terminology and Editorial.
trator Terrestrial Photovoltaic Modules and Systems Un-
Current edition approved Nov. 1, 2021. Published November 2021. Originally
der Natural Sunlight
approved in 1980. Last previous edition approved in 2015 as E772–15. DOI:
10.1520/E0772-15R21.
F1863Test Method for Measuring the NightVision Goggle-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Weighted Transmissivity of Transparent Parts
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
G113Terminology Relating to Natural andArtificialWeath-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. ering Tests of Nonmetallic Materials
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E772 − 15 (2021)
G130Test Method for Calibration of Narrow- and Broad- absorption, n—transformation of radiant energy to a different
Band Ultraviolet Radiometers Using a Spectroradiometer form of energy by interaction with matter. E349
G138Test Method for Calibration of a Spectroradiometer
aerosol, n—any solid or liquid particles, with a nominal size
Using a Standard Source of Irradiance
range from 10 nm to 100 µm, suspended in a gas (usually
G167Test Method for Calibration of a Pyranometer Using a
air). D5544
Pyrheliometer
G173TablesforReferenceSolarSpectralIrradiances:Direct
aerosol optical depth, AOD, n—a measure of the extinction
Normal and Hemispherical on 37° Tilted Surface
caused by aerosols in the atmosphere relative to the zenith
G197Table for Reference Solar Spectral Distributions: Di-
and modeled with Ångstrom’s turbidity formula.
rect and Diffuse on 20° Tilted and Vertical Surfaces
DISCUSSION—Although it varies with wavelength, it is common to
IEEE/ASTM SI 10American National Standard for Metric
report aerosol optical depth at a single wavelength only, especially 0.5
Practice µm.
2.2 ISO Standard:
air mass, AM, n—relative optical mass (see optical mass,
ISO9060SpecificationandClassificationofInstrumentsfor
relative) calculated using the density of air as a function of
Measuring Hemispherical Solar and Direct Solar Radiai-
altitude.
ton
AM'l /l 5 secθ , for θ #1 rad ~60°! (1)
s z z z
2.3 WMO Document:
DISCUSSION—Eq 1 is a simple approximation of the optical mass,
WMO-No. 8Guide to Meteorological Instruments and
relative (see Eq 5) that uses the ratio of the path length along the sun
Methods of Observation, Seventh ed., 2008, World Me-
vector (l ) to the path length along the zenith (l ) (see sun vector,
s z
teorological Organization (WMO), Geneva
zenith,and zenith angle, solar).Othersolutionsaremorecomplicated
and take factors such as refraction and local air pressure into account.
3. Adjectives for Electromagnetic Radiation
DISCUSSION—Theabbreviation AMisalsocommonlyusedtoreferto
3.1 Properties and quantities associated with electromag-
aparticularstandardsolarspectralirradiance,suchasthoseinStandard
netic radiation vary with: E490, Tables G173, and Table G197. Thus, AM0 can indicate the
extraterrestrial spectral irradiance table in Standard E490, and AM1.5
3.1.1 The direction and geometric extent (solid angle) over
the hemispherical spectral irradiance table in Tables G173. Using
which the incident or exitant flux, or both, is evaluated, and
AM1.5 in this way is discouraged because air mass is but one of many
3.1.2 The relative spectral distribution of the incident flux
variables that modify solar spectral irradiance such as clouds, aerosol
and the spectral response of the detector for exitant flux.
scattering, and water vapor absorption; note that bothTables G173 and
Table G197 use an air mass value of 1.5, but differ greatly. The
3.2 Adjective modifiers can be used to indicate the
distinction between a spectral irradiance and a path length ratio should
geometric, spectral, and polarization conditions under which
be made clear whenever these abbreviations are used.
radiometric properties and quantities are evaluated. The adjec-
tives defined in this Terminology are: conical, diffuse, direct,
air mass one, AM1, n—a relative optical mass (see optical
directional, hemispherical, luminous, normal, and spectral.
mass, relative) that is equal to one. Because of the way in
which relative optical mass is defined,AM1 always denotes
3.3 For reflectance and transmittance, the direction and
a vertical path at sea level.
geometric extent of both the incident beam and exitant beam
must be specified.
air mass, optical—see optical mass, relative.
3.4 For emittance, only the exitant beam need be specified,
air mass, pressure corrected, AM , n—an approximation of
and for absorptance, only the incident beam need be specified. p
air mass for locations above sea level that uses the ratio of
3.5 Radiometricpropertiesalsovarywiththepolarizationof
the local barometric pressure P, to the standard sea level
the incident flux and the sensitivity to polarization of the
atmospheric pressure P = 101.325 kPa (see Eq 2).
collector-detector system for flux incident or exitant at angles
P
greater than about 15° from normal.
AMp' AM (2)
P
3.6 An instrument used for solar energy measurements or a
solar energy receiver will usually determine the directions and air mass ratio—see optical mass, relative.
geometric extents, such as a pyranometer, a pyrheliometer, or
air mass, relative optical—see optical mass, relative.
a flat-plate solar thermal collector.
air mass zero, AM0, n—the absence of atmospheric attenua-
4. Terminology
tion of the solar irradiance at one astronomical unit from the
sun. E491
ELECTROMAGNETIC RADIATION AND OPTICS
albedo—discouraged in favor of the preferred term, reflec-
absorptance, n—ratiooftheabsorbedradiantorluminousflux
tance.
to the incident flux. E349
angle of incidence, rad or °, n—the angle between a ray and
the normal vector to the plane on which the ray is incident;
Available from International Organization for Standardization (ISO), 1, ch. de
especially the angle between the sun vector and the normal
la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http://www.iso.org.
Available from World Meteorological Organization, http://www.wmo.int. vector.
E772 − 15 (2021)
angle of reflection,rador°, n—theanglebetweenthedirection diffusion, n—change of the spatial distribution of a beam of
ofpropagationofareflectedrayandthenormalvectortothe radiation when it is deviated in many directions by a surface
surface of interest at the point of reflection. or a medium. E349
angle of refraction, rad or °, n—the angle between the direct, adj—describing solar radiation, a collimated beam.
direction of propagation of a refracted ray and the normal
directional, adj—of or relating to a direction in space.
vector to the interface of interest at the point of refraction.
DISCUSSION—Foropticalproperties,overaninfinitesimalsolidangle,
thepropertyisassumedconstant.Thevariationinopticalpropertywith
altitude angle, solar—see elevation angle, solar.
respect to changing azimuth (counter-clockwise) and incidence angle
attenuation—see extinction. (from the surface normal), with respect to a reference mark on a
sample, is the directional response.
azimuth angle, solar, ψ[rad or °], n—the angle between the
elevation angle, solar, α [rad or °], n—the complement of the
line of longitude (or geographical meridian) at the location
solar zenith angle, i.e. π/2 – θ radians. See zenith angle,
of interest and the horizontal component of the sun vector. z
solar.
Byconvention,theazimuthangleispositivewhenthesunis
east of the line of longitude and negative when it is west of
emission, n—release of radiant energy. E349
the line of longitude.
emissive power—discouraged in favor of the preferred term
beam, n—of radiant energy, a collection of rays confined to a
radiant exitance.
specific path.
emittance, ε, n— for a sample at a given temperature, ratio of
blackbody, Planckian radiator, n—a thermal radiator which
the radiant flux emitted by a sample to that emitted by a
completely absorbs all incident radiation, whatever the
blackbody radiator at the same temperature, under the same
wavelength, the direction of incidence, or the polarization.
spectral and geometric conditions of measurement.
Thisradiatorhas,foranywavelength,themaximumspectral
concentration of radiant exitance at a given temperature. extinction, n—the attenuation of radiant energy from an
incident beam by the processes of molecular absorption and
E491
scattering caused by atmospheric constituents.
Bouguer’s Law, n—an expression of the extinction of radia-
DISCUSSION—Scattering by air molecules can be modeled with
tion in a medium that states the intensity exponentially
Rayleigh scattering, and scattering by aerosols with Ångstrom’s
decreases due to both scattering and absorption as it passes
turbidity formula. Absorption processes are modeled with tables of
through the medium (see Eq 3), where τ is the wavelength- measured absorption coefficients versus wavelength.
λ
dependent extinction optical thickness. The ratio of I to I
extinction coefficient, monochromatic, k [dimensionless],
iλ
is equal to the atmospheric transmittance, T, and τ is equal
λ
n—a measure of the extinction caused by a particular
to the summation of the extinction optical thicknesses
atmosphericconstituent(see Bouguer’s Lawand extinction
associated with each individual scattering or absorption
optical thickness, monochromatic).
process τ .
iλ
n
extinction optical depth, monochromatic, [dimensionless],
I 5 I exp 2τ 5 I exp 2 τ (3)
~ ! S D
0 λ 0 ( iλ
n—theproductofthe extinction coefficient k foraparticu-
iλ
i51
laratmosphericconstituenttimesthepathlengthtothetopof
DISCUSSION—Bouguer’s Law is also known as Lambert’s Law or
theatmosphere, m ,see extinction optical thickness, mono-
Beer’s Law.
r
chromatic and optical mass, relative.
circumsolar diffuse radiation—see radiant energy, circumso-
DISCUSSION—Optical depth is sometimes used synonymously with
lar.
optical thickness, but the preferred distinction between the two is that
optical thickness refers to the extinction along the entire path through
conical, adj—describing a solid angle larger than an infinitesi-
the atmosphere rather than the vertical path.
malelementandlessthanahemisphere(2πsr);thegeometry
extinction optical thickness, monochromatic, τ
of the solid angle must be described in context.
iλ
[dimensionless], n—theproductofthe extinction coefficient
diffuse, adj—describing radiometric quantities, indicates flux
k for a particular atmospheric constituent times the path
iλ
propagating in many directions, as opposed to a collimated
lengththroughatmosphere,see Bouguer’s LawandEq4,in
beam.
which m is the optical mass, actual.
act
τ 5 k ·m (4)
diffuse, adj—describing solar irradiance, the global hemi-
iλ iλ act
spherical irradiance minus the direct beam irradiance.
hemispherical, adj—describing half of a sphere, i.e. a 2π sr
solid angle.
diffuse, adj—describing reflectance
...
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