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ASTM E948-95(2001)

(Test Method)

Standard Test Method for Electrical Performance of Photovoltaic Cells Using Reference Cells Under Simulated Sunlight

Standard Test Method for Electrical Performance of Photovoltaic Cells Using Reference Cells Under Simulated Sunlight

SCOPE
1.1 This test method covers the determination of the electrical performance of a photovoltaic cell under simulated sunlight by means of a calibrated reference cell procedure.  
1.2 Electrical performance measurements are reported with respect to a select set of standard reporting conditions (SRC) (see Table 1) or to user-specified conditions.  
1.2.1 The SRC or user-specified conditions include the cell temperature, the total irradiance, and the reference spectral irradiance distribution.  
1.3 This test method is applicable only to photovoltaic cells with a linear response over the range of interest.  
1.4 The cell parameters determined by this test method apply only at the time of test, and imply no past or future performance level.  
1.5 There is no similar or equivalent ISO standard.  
1.6 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

Status
Historical
Publication Date
09-Oct-1995
ICS
27.160 - Solar energy engineering
Technical Committee
E44 - Solar, Geothermal and Other Alternative Energy Sources
Drafting Committee
E44.09 - Photovoltaic Electric Power Conversion
Current Stage
Ref Project

Relations

Replaces
ASTM E948-95 - Standard Test Method for Electrical Performance of Photovoltaic Cells Using Reference Cells Under Simulated Sunlight
Effective Date
10-Oct-1995
Replaced By
ASTM E948-05 - Standard Test Method for Electrical Performance of Photovoltaic Cells Using Reference Cells Under Simulated Sunlight
Effective Date
01-Apr-2005
Referred By
ASTM E1021-15(2019) - Standard Test Method for Spectral Responsivity Measurements of Photovoltaic Devices
Effective Date
10-Oct-1995
Referred By
ASTM E2236-10(2019) - Standard Test Methods for Measurement of Electrical Performance and Spectral Response of Nonconcentrator Multijunction Photovoltaic Cells and Modules
Effective Date
10-Oct-1995
Referred By
ASTM E1040-10(2020) - Standard Specification for Physical Characteristics of Nonconcentrator Terrestrial Photovoltaic Reference Cells
Effective Date
10-Oct-1995
Referred By
ASTM E1125-16(2020) - Standard Test Method for Calibration of Primary Non-Concentrator Terrestrial Photovoltaic Reference Cells Using a Tabular Spectrum
Effective Date
10-Oct-1995
Referred By
ASTM E1036-15(2019) - Standard Test Methods for Electrical Performance of Nonconcentrator Terrestrial Photovoltaic Modules and Arrays Using Reference Cells
Effective Date
10-Oct-1995
Referred By
ASTM E2848-13(2023) - Standard Test Method for Reporting Photovoltaic Non-Concentrator System Performance
Effective Date
10-Oct-1995
Referred By
ASTM E772-15(2021) - Standard Terminology of Solar Energy Conversion
Effective Date
10-Oct-1995
Referred By
ASTM E973-16(2020) - Standard Test Method for Determination of the Spectral Mismatch Parameter Between a Photovoltaic Device and a Photovoltaic Reference Cell
Effective Date
10-Oct-1995
Referred By
ASTM E1143-05(2019) - Standard Test Method for Determining the Linearity of a Photovoltaic Device Parameter with Respect To a Test Parameter
Effective Date
10-Oct-1995
Referred By
ASTM E927-19 - Standard Classification for Solar Simulators for Electrical Performance Testing of Photovoltaic Devices
Effective Date
10-Oct-1995
Referred By
ASTM E1362-15(2019) - Standard Test Methods for Calibration of Non-Concentrator Photovoltaic Non-Primary Reference Cells
Effective Date
10-Oct-1995

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ASTM E948-95(2001) - Standard Test Method for Electrical Performance of Photovoltaic Cells Using Reference Cells Under Simulated SunlightASTM E948-95(2001) - Standard Test Method for Electrical Performance of Photovoltaic Cells Using Reference Cells Under Simulated Sunlight
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ASTM E948-95(2001) - Standard Test Method for Electrical Performance of Photovoltaic Cells Using Reference Cells Under Simulated Sunlight
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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:E948–95 (Reapproved 2001)
Standard Test Method for
Electrical Performance of Photovoltaic Cells Using
Reference Cells Under Simulated Sunlight
This standard is issued under the fixed designation E948; 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 (e) indicates an editorial change since the last revision or reapproval.
TABLE 1 Standard Reporting Conditions
1. Scope
1.1 This test method covers the determination of the elec- NOTE 1—The extraterrestrial solar constant and spectral irradiance
contained in Tables E490 do not represent the latest measurements of
trical performance of a photovoltaic cell under simulated
these quantities. The World Radiation Center recommends a value of
sunlight by means of a calibrated reference cell procedure.
−2
1367Wm for the solar constant along with more reliable measurements
1.2 Electrical performance measurements are reported with
of the extraterrestrial spectral irradiance.
respect to a select set of standard reporting conditions (SRC)
Reference Spectral Irradiance Total Irradiance Temperature
(see Table 1) or to user-specified conditions.
−2
Distribution (Wm ) (°C)
1.2.1 The SRC or user-specified conditions include the cell
Tables E 891 1000 25
temperature, the total irradiance, and the reference spectral
Tables E 892 1000 25
irradiance distribution. Tables E 490 1353 25
1.3 This test method is applicable only to photovoltaic cells
with a linear response over the range of interest.
1.4 The cell parameters determined by this test method
E927 Specification for Solar Simulation for Terrestrial
apply only at the time of test, and imply no past or future
Photovoltaic Testing
performance level.
E973 Test Method for Determination of the Spectral Mis-
1.5 There is no similar or equivalent ISO standard.
match Parameter Between a Photovoltaic Device and a
1.6 This standard does not purport to address all of the
Photovoltaic Reference Cell
safety concerns, if any, associated with its use. It is the
E1021 Test Methods for Measuring Spectral Response of
responsibility of the user of this standard to establish appro-
Photovoltaic Cells
priate safety and health practices and determine the applica-
E 1039 Test Method for Calibration of Silicon Non-
bility of regulatory limitations prior to use.
Concentrator Photovoltaic Primary Reference Cells Under
Global Irradiation
2. Referenced Documents
E1040 Specification for Physical Characteristics of Non-
2.1 ASTM Standards:
concentrator Terrestrial Photovoltaic Reference Cells
E490 Solar Constant and Zero Air Mass Solar Spectral
E1125 Test Method for Calibration of Primary Non-
Irradiance Tables
Concentrator Terrestrial Photovoltaic Reference Cells Us-
E491 Practice for Solar Simulation for Thermal Balance
ing a Tabular Spectrum
Testing of Spacecraft
E1328 Terminology Relating to Photovoltaic Solar Energy
E691 Practice for Conducting an Interlaboratory Study to
Conversion
Determine the Precision of a Test Method
E1362 Test Method for Calibration of Non-Concentrator
E772 Terminology Relating to Solar Energy Conversion
Photovoltaic Secondary Reference Cells
E891 Terrestrial Direct Normal Solar Spectral Irradiance
Tables for Air Mass 1.5
3. Terminology
E892 Tables for Terrestrial Solar Spectral Irradiance atAir
3.1 Definitions—Definitions of terms in this test method
Mass 1.5 for a 37° Tilted Surface
may be found in Terminology E772 and Terminology E1328.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 cell temperature, °C, n—the temperature of the semi-
1 conductor junction of a photovoltaic cell.
This test method is under the jurisdiction of ASTM Committee E44 on Solar,
3.2.2 junction temperature, n—synonym for cell tempera-
Geothermal,andOtherAlternativeEnergySourcesandisthedirectresponsibilityof
Subcommittee E44.09 on Photovoltaic Electric Power Conversion.
ture.
Current edition approved Oct. 10, 1995. Published March 1996.
3.2.3 light source, n—a source of radiant energy used for
Annual Book of ASTM Standards, Vol 15.03.
cellperformancemeasurementsthatsimulatesnaturalsunlight.
Annual Book of ASTM Standards, Vol 14.02.
Annual Book of ASTM Standards, Vol 12.02. 3.3 Symbols:Symbols:
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E948
3.3.1 The following symbols and units are used in this test such as different manufacturers’ products. Repeated measure-
method: ments of the same cell may be used to study changes in device
A—cell area, m performance.
−1
a —temperature coefficient of reference cell,° C 5.3 This test method determines the electrical performance
r
2 −1
C—calibration constant of reference cell, Am W of a cell based upon the output power at a single instant of
−2
E—irradiance, Wm time. It does not provide for integrating the output power over
−2
E —standard reporting irradiance, Wm a given period of time and conditions to predict an energy
o
h—efficiency, % output.
FF—fill factor, % 5.4 Thistestmethodrequiresareferencecellcalibratedwith
I—current, A respect to an appropriate reference spectral irradiance distribu-
I —current with respect to SRC, A tion, such as Tables E490, E891, or E892. It is the respon-
o
I —reference cell short-circuit current, A sibility of the user to determine which reference spectral
r
I —short-circuit current, A irradiance distribution is appropriate for a particular applica-
sc
M—spectral mismatch parameter tion.
P —maximum power, W
m
R —series resistance, V
6. Apparatus
s
T—temperature,° C
6.1 Photovoltaic Reference Cell—A calibrated reference
T —standard reporting temperature,° C
o
cell is used to determine the total irradiance during the
T —temperature of reference cell,° C
r
electrical performance measurement.
V—voltage, V
6.1.1 Reference cells may be calibrated in accordance with
V —voltage with respect to SRC, V
o
Test Methods E1039, E1125, or E1362, as is appropriate for
V —open-circuit voltage, V
oc
a particular application.
NOTE 1—No reference cell calibration standards presently exist for
4. Summary of Test Method
space applications, although procedures such as high-altitude balloon and
4.1 The performance test of a photovoltaic cell consists of
low-earth orbit flights are being used to calibrate such reference cells.
measuring the electrical current versus voltage (I-V) charac-
6.1.2 A current measurement instrument (see 6.3) shall be
teristic of the cell while illuminated by a suitable light source.
used to determine the I of the reference cell under the light
sc
4.2 Acalibratedphotovoltaicreferencecell(see6.1)isused
source.
to determine the total irradiance during the test and to account
6.2 Test Fixture— Both the cell to be tested and the
for the spectral distribution of the light source.
referencecellaremountedinafixturethatmeetsthefollowing
4.3 Simulated sunlight is used as the light source for the
requirements.
electrical performance measurement, and solar simulation
6.2.1 Thetestfixtureshallensureauniformlateraltempera-
requirements are defined in Specification E927 (terrestrial
ture distribution to within 60.5°C during the performance
applications) and Practice E491 (space applications).
measurement.
4.4 The data from the measurements are corrected to stan-
6.2.2 The test fixture shall include a provision for maintain-
dard reporting conditions, or to optional user-specified report-
ing a constant cell temperature for both the reference cell and
ingconditions.Thestandardreportingconditionsaredefinedin
the cell to be tested (see 7.6.1).
Table 1.
4.4.1 Measurement error caused by deviations of the irradi- NOTE 2—When using pulsed or shuttered light sources, it is possible
thatthecelltemperaturewillincreaseuponinitialillumination,evenwhen
ance conditions from the SRC is corrected using the total
the cell temperature is controlled.
irradiance measured with the reference cell and the spectral
mismatch parameter, M, which is determined in accordance
6.2.3 Thetestfixture,whenplacedinthesimulatedsunlight,
with Test Method E973.
shallensurethatthefield-of-viewofboththereferencecelland
4.4.2 Measurement error caused by deviation of the cell
the cell to be tested are identical.
temperaturefromtheSRCisminimizedbymaintainingthecell
NOTE 3—Some solar simulators may have significant amounts of
temperature close to the required value (see 7.6.1).
irradiation from oblique or non-perpendicular angles to the test plane. In
these cases, it is important that the cell to be tested and the reference cell
5. Significance and Use
have similar reflectance and cosine-response characteristics.
5.1 It is the intent of this test method to provide a recog-
6.2.4 A four-terminal connection (also known as a Kelvin
nized method for testing and reporting the electrical perfor-
connection, see Fig. 1) from the cell to be tested to the I-V
mance of photovoltaic cells.
measurement instrumentation (see 6.3-6.5) shall be used.
5.2 The test results may be used for comparison of cells
6.3 Current Measurement Equipment— The instrument or
among a group of similar cells or to compare diverse designs,
instruments used to measure the cell current and the I of the
sc
reference cell shall have a resolution of at least 0.02% of the
maximum current encountered, and shall have a total error of
less than 0.1% of the maximum current encountered.
Wehrli, C., Extraterrestrial Solar Spectrum, Publ. No. 615, Physikalisch-
6.4 Voltage Measurement Equipment—The instrument or
Meteorologisches Observatorium and World Radiation Center, Davos Switzerland,
1985. instruments used to measure the cell voltage shall have a
E948
7.1.1 If the total irradiance during the performance mea-
surement as measured by the reference cell is within 62%of
the standard reporting total irradiance, the series resistance is
not needed.
7.2 Measure the cell area, A, using the definition in Termi-
nology E1328.
7.3 Determine the spectral mismatch parameter, M, using
Test Method E973.
7.4 Mount the cell to be tested and the reference cell in the
test fixture.
NOTE 5—Any nonuniformity of irradiance (see Specification E927)
between the locations of the reference cell and the cell to be tested will
introduce a bias error in the measured cell performance.
7.4.1 Ifapulsedorshutteredlightsourceisused,exposethe
test fixture to the source illumination.
FIG. 1 I-V Measurement Schematic
7.5 Measure the temperature of the reference cell, T .
r
7.5.1 If the temporal instability of the light source (as
defined in Specification E927) is less than 0.1%, the total
resolution of at least 0.02% of the maximum voltage encoun-
irradiance may be determined with the reference cell prior to
tered, and shall have a tota
...

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FIG. 1 Hot Spot Effect  
4.5 Bypass diodes, if present, as shown in Fig. 2, begin conducting when a series-connected string in a module is in reverse bias, thereby limiting the power dissipation in the reduced-output cell.  
FIG. 2 Bypass Diode Effect  
Note 2: If the ...
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1.1 This test method provides a procedure to determine the ability of a photovoltaic (PV) module to endure the long-term effects of periodic “hot spot” heating associated with common fault conditions such as severely cracked or mismatched cells, single-point open circuit failures (for example, interconnect failures), partial (or nonuniform) shadowing, or soiling. Such effects typically include solder melting or deterioration of the encapsulation, but in severe cases could progress to combustion of the PV module and surrounding materials.  
1.2 There are two ways that cells can cause a hot spot problem: either by having a high resistance so that there is a large resistance in the circuit, or by having a low resistance area (shunt) such that there is a high current flow in a localized region. This test method selects cells of both types to be stressed.  
1.3 This test method does not establish pass or fail levels. The determination of acceptable or unacceptable results is beyond the scope of this test method.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 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.  
1.6 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.

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ASTM E781-86(2023)(Practice)
Standard Practice for Evaluating Absorptive Solar Receiver Materials When Exposed to Conditions Simulating Stagnation in Solar Collectors with Cover Plates

SIGNIFICANCE AND USE
4.1 Although this practice is intended for evaluating solar absorber materials and coatings used in flat-plate collectors, no single procedure can duplicate the wide range of temperatures and environmental conditions to which these materials may be exposed during in-service conditions.  
4.2 This practice is intended as a screening test for absorber materials and coatings. All conditions are chosen to be representative of those encountered in solar collectors with single cover plates and with no added means of limiting the temperature during stagnation conditions.  
4.3 This practice uses exposure in a simulated collector with a single cover plate. Although collectors with additional cover plates will produce higher temperatures at stagnation, this procedure is considered to provide adequate thermal testing for most applications.
Note 1: Mathematical modeling has shown that a selective absorber, single glazed flat-plate solar collector can attain absorber plate stagnation temperatures as high as 226 °C (437 °F) with an ambient temperature of 37.8 °C (100 °F) and zero wind velocity, and a double glazed one as high as 245 °C (482 °F) under these conditions. The same configuration solar collector with a nonselective absorber can attain absorber stagnation temperatures as high as 146 °C (284 °F) if single glazed, and 185 °C (360 °F) if double glazed, with the same environmental conditions (see “Performance Criteria for Solar Heating and Cooling Systems in Commercial Buildings,” NBS Technical Note 1187).4  
4.4 This practice evaluates the thermal stability of absorber materials. It does not evaluate the moisture stability of absorber materials used in actual solar collectors exposed outdoors. Moisture intrusion into solar collectors is a frequent occurrence in addition to condensation caused by diurnal breathing.  
4.5 This practice differentiates between the testing of spectrally selective absorbers and nonselective absorbers.  
4.5.1 Testing Spectrally Selective...
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1.1 This practice covers a test procedure for evaluating absorptive solar receiver materials and coatings when exposed to sunlight under cover plate(s) for long durations. This practice is intended to evaluate the exposure resistance of absorber materials and coatings used in flat-plate collectors where maximum non-operational stagnation temperatures will be approximately 200 °C (392 °F).  
1.2 This practice shall not apply to receiver materials used in solar collectors without covers (unglazed) or in evacuated collectors, that is, those that use a vacuum to suppress convective and conductive thermal losses.  
1.3 The values stated in SI units are to be regarded as the standard.  
1.4 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.  
1.5 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.

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ASTM E822-92(2023)(Practice)
Standard Practice for Determining Resistance of Solar Collector Covers to Hail by Impact with Propelled Ice Balls

SIGNIFICANCE AND USE
2.1 In many geographic areas there is concern about the effect of falling hail upon solar collector covers. This practice may be used to determine the ability of flat-plate solar collector covers to withstand the impact forces of hailstones. In this practice, the ability of a solar collector cover plate to withstand hail impact is related to its tested ability to withstand impact from ice balls. The effects of the impact on the material are highly variable and dependent upon the material.  
2.2 This practice describes a standard procedure for mounting the test specimen, conducting the impact test, and reporting the effects.  
2.2.1 The procedures for mounting cover plate materials and collectors are provided to ensure that they are tested in a configuration that relates to their use in a solar collector.  
2.2.2 The corner locations of the four impacts are chosen to represent vulnerable sites on the cover plate. Impacts near corner supports are more critical than impacts elsewhere. Only a single impact is specified at each of the impact locations. For test control purposes, multiple impacts in a single location are not permitted because a subcritical impact may still cause damage that would alter the response to subsequent impacts.  
2.2.3 Resultant velocity is used to simulate the velocity that may be reached by hail accompanied by wind. The resultant velocity used in this practice is determined by vector addition of a 20 m/s (45 mph) horizontal velocity to the vertical terminal velocity.  
2.2.4 Ice balls are used in this practice to simulate hailstones because natural hailstones are not readily available to use, and ice balls closely approximate hailstones. However, no direct relationship has been established between the effect of impact of ice balls and hailstones. Hailstones are highly variable in properties such as shape, density, and frangibility.2 These properties affect factors such as the kinetic energy delivered to the cover plate, the period during ...
SCOPE
1.1 This practice covers a procedure for determining the ability of cover plates for flat-plate solar collectors to withstand impact forces of falling hail. Propelled ice balls are used to simulate falling hailstones. This practice is not intended to apply to photovoltaic cells or arrays.  
1.2 This practice defines two types of test specimens, describes methods for mounting specimens, specifies impact locations on each test specimen, provides an equation for determining the velocity of any size ice ball, provides a method for impacting the test specimens with ice balls, and specifies parameters that must be recorded and reported.  
1.3 This practice does not establish pass or fail levels. The determination of acceptable or unacceptable levels of ice-ball impact resistance is beyond the scope of this practice.  
1.4 The size of ice ball to be used in conducting this test is not specified in this practice. This practice can be used with various sizes of ice balls.  
1.5 The categories of solar collector cover plate materials to which this practice may be applied cover the range of:  
1.5.1 Brittle sheet, such as glass,  
1.5.2 Semirigid sheet, such as plastic, and  
1.5.3 Flexible membrane, such as plastic film.  
1.6 Solar collector cover materials should be tested as:  
1.6.1 Part of an assembled collector (Type 1 specimen), or  
1.6.2 Mounted on a separate test frame cover plate holder (Type 2 specimen).  
1.7 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.  
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 internatio...

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ASTM E881-92(2022)(Practice)
Standard Practice for Exposure of Solar Collector Cover Materials to Natural Weathering Under Conditions Simulating Stagnation Mode

SIGNIFICANCE AND USE
4.1 This practice describes a weathering box test fixture and establishes limits for the heat loss coefficients. Uniform exposure guidelines are provided to minimize the variables encountered during outdoor exposure testing.  
4.2 Since the combination of elevated temperature and solar radiation may cause some solar collector cover materials to degrade more rapidly than either exposure alone, a weathering box that elevates the temperature of the cover materials is used.  
4.3 This practice may be used to assist in the evaluation of solar collector cover materials in the stagnation mode. No single temperature or procedure can duplicate the range of temperatures and environmental conditions to which cover materials may be exposed during stagnation conditions. To assist in evaluation of solar collector cover materials in the operational mode, Practice E782 should be used. Insufficient data exist to obtain exact correlation between the behavior of materials exposed in accordance with this practice and actual in-service performance.  
4.4 This practice may also be useful in comparing the performance of different materials at one site or the performance of the same material at different sites, or both.  
4.5 Means of evaluating the effects of weathering are provided in Practice E765, and in other ASTM test methods that evaluate material properties.  
4.6 Exposures of the type described in this practice may be used to evaluate the stability of solar collector cover materials when exposed outdoors to the varied influences that comprise weather. Exposure conditions are complex and changeable. Important factors are material temperature, climate, time of year, presence of industrial pollution, etc. Generally, because it is difficult to define or measure precisely the factors influencing degradation due to weathering, results of outdoor exposure tests must be taken as indicative only. Repeated exposure testing at different seasons over a period of more than one year is req...
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1.1 This practice covers a procedure for the exposure of solar collector cover materials to the natural weather environment at elevated temperatures that approximate stagnation conditions in solar collectors having a combined back and edge loss coefficient of less than 1.5 W/(m2·°C).  
1.2 This practice is suitable for exposure of both glass and plastic solar collector cover materials. Provisions are made for exposure of single and double cover assemblies to accommodate the need for exposure of both inner and outer solar collector cover materials.  
1.3 This practice does not apply to cover materials for evacuated collectors, photovoltaic cells, flat-plate collectors having a combined back and edge loss coefficient greater than 1.5 W/(m2·°C), or flat-plate collectors whose design incorporates means for limiting temperatures during stagnation.  
1.4 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.  
1.5 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.

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ASTM E782-95(2022)(Practice)
Standard Practice for Exposure of Cover Materials for Solar Collectors to Natural Weathering Under Conditions Simulating Operational Mode

SIGNIFICANCE AND USE
3.1 This practice describes a weathering box test fixture and provides uniform exposure guidelines to minimize the variables encountered during outdoor exposure testing.  
3.2 This practice may be useful in comparing the performance of different materials at one site or the performance of the same material at different sites, or both.  
3.3 Since the combination of elevated temperature and solar radiation may cause some solar collector cover materials to degrade more rapidly than either alone, a weathering box that elevates the temperature of the cover materials is used.  
3.4 This practice is intended to assist in the evaluation of solar collector cover materials in the operational, not stagnation mode. Insufficient data exist to obtain exact correlation between the behavior of materials exposed according to this practice and actual in-service performance.  
3.5 Means of evaluation of effects of weathering are provided in Practice E781, and in other ASTM test methods that evaluate material properties.  
3.6 Tests of the type described in this practice may be used to evaluate the stability of solar collector cover materials when exposed outdoors to the varied influences which comprise weather. Exposure conditions are complex and changeable. Important factors are solar radiation, temperature, moisture, time of year, presence of pollutants, etc. These factors vary from site to site and should be considered in selecting locations for exposure. Control samples must always be used in weathering tests for comparative analysis. Outdoor exposure for at least two years is required to make evident changes, such as surface degradation without the use of sophisticated analytical equipment.  
3.7 Temperature conditions attained with this box may not exactly duplicate those that occur under operational conditions with fluid flow. Dependent on environmental exposure conditions, the cover plate temperatures obtained with this box may be higher or lower than those obtained und...
SCOPE
1.1 This practice provides a procedure for the exposure of cover materials for flat-plate solar collectors to the natural weather environment at temperatures that are elevated to approximate operating conditions.  
1.2 This practice is suitable for exposure of both glass and plastic solar collector cover materials. Provisions are made for exposure of single and double cover assemblies to accommodate the need for exposure of both inner and outer solar collector cover materials.  
1.3 This practice does not apply to cover materials for evacuated collectors or photovoltaics.  
1.4 The values stated in SI units are to be regarded as the standard.  
1.5 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.  
1.6 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.

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