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ASTM E782-95(2007)

(Practice)

Standard Practice for Exposure of Cover Materials for Solar Collectors to Natural Weathering Under Conditions Simulating Operational Mode

Standard Practice for Exposure of Cover Materials for Solar Collectors to Natural Weathering Under Conditions Simulating Operational Mode

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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

Status
Historical
Publication Date
28-Feb-2007
ICS
27.160 - Solar energy engineering
Technical Committee
E44 - Solar, Geothermal and Other Alternative Energy Sources
Current Stage
Ref Project

Relations

Replaces
ASTM E782-95(2001) - Standard Practice for Exposure of Cover Materials for Solar Collectors to Natural Weathering Under Conditions Simulating Operational Mode
Effective Date
01-Mar-2007
Referred By
ASTM E881-92(2022) - Standard Practice for Exposure of Solar Collector Cover Materials to Natural Weathering Under Conditions Simulating Stagnation Mode
Effective Date
01-Mar-2007

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ASTM E782-95(2007) - Standard Practice for Exposure of Cover Materials for Solar Collectors to Natural Weathering Under Conditions Simulating Operational ModeASTM E782-95(2007) - Standard Practice for Exposure of Cover Materials for Solar Collectors to Natural Weathering Under Conditions Simulating Operational Mode
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ASTM E782-95(2007) - Standard Practice for Exposure of Cover Materials for Solar Collectors to Natural Weathering Under Conditions Simulating Operational Mode
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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: E782 − 95(Reapproved 2007)
Standard Practice for
Exposure of Cover Materials for Solar Collectors to Natural
Weathering Under Conditions Simulating Operational Mode
This standard is issued under the fixed designation E782; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Significance and Use
1.1 This practice provides a procedure for the exposure of
3.1 This practice describes a weathering box test fixture and
cover materials for flat-plate solar collectors to the natural provides uniform exposure guidelines to minimize the vari-
weather environment at temperatures that are elevated to
ables encountered during outdoor exposure testing.
approximate operating conditions.
3.2 This practice may be useful in comparing the perfor-
1.2 This practice is suitable for exposure of both glass and
mance of different materials at one site or the performance of
plastic solar collector cover materials. Provisions are made for the same material at different sites, or both.
exposure of single and double cover assemblies to accommo-
3.3 Since the combination of elevated temperature and solar
date the need for exposure of both inner and outer solar
radiation may cause some solar collector cover materials to
collector cover materials.
degrade more rapidly than either alone, a weathering box that
1.3 This practice does not apply to cover materials for
elevates the temperature of the cover materials is used.
evacuated collectors or photovoltaics.
3.4 This practice is intended to assist in the evaluation of
1.4 The values stated in SI units are to be regarded as the
solar collector cover materials in the operational, not stagna-
standard.
tion mode. Insufficient data exist to obtain exact correlation
between the behavior of materials exposed according to this
1.5 This standard does not purport to address all of the
practice and actual in-service performance.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.5 Means of evaluation of effects of weathering are pro-
priate safety and health practices and determine the applica-
vided in Practice E781, and in other ASTM test methods that
bility of regulatory limitations prior to use.
evaluate material properties.
3.6 Tests of the type described in this practice may be used
2. Referenced Documents
to evaluate the stability of solar collector cover materials when
2.1 ASTM Standards:
exposed outdoors to the varied influences which comprise
E781 Practice for Evaluating Absorptive Solar Receiver
weather. Exposure conditions are complex and changeable.
Materials When Exposed to Conditions Simulating Stag-
Important factors are solar radiation, temperature, moisture,
nation in Solar Collectors With Cover Plates
time of year, presence of pollutants, etc. These factors vary
E881 Practice for Exposure of Solar Collector Cover Mate-
from site to site and should be considered in selecting locations
rials to Natural Weathering Under Conditions Simulating
for exposure. Control samples must always be used in weath-
Stagnation Mode
ering tests for comparative analysis. Outdoor exposure for at
G7 Practice for Atmospheric Environmental Exposure Test-
least two years is required to make evident changes, such as
ing of Nonmetallic Materials
surface degradation without the use of sophisticated analytical
equipment.
3.7 Temperature conditions attained with this box may not
These test methods are under the jurisdiction of ASTM Committee E44 on
exactly duplicate those that occur under operational conditions
Solar, Geothermal and Other Alternative Energy Sources and is the direct respon-
sibility of Subcommittee E44.05 on Solar Heating and Cooling Systems and with fluid flow. Dependent on environmental exposure
Materials.
conditions, the cover plate temperatures obtained with this box
Current edition approved March 1, 2007. Published April 2007. Originally
may be higher or lower than those obtained under operational
approved in 1981. Last previous edition approved in 2001 as E782 – 95 (2001).
conditions. Additional testing under stagnation conditions,
DOI: 10.1520/E0782-95R07.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
although not covered by this practice should be conducted.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on NOTE 1—Research has shown that exposure outdoors at sites having the
the ASTM website. combination of high levels of humidity, solar energy, and ambient
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E782 − 95 (2007)
temperature can cause more severe degradation of some polymeric cover
materials, (for example, microcracking and leaching of UV radiation
screening additives) than exposure in arid climates.
NOTE 2—Stagnation conditions are a normal occurrence for solar
collectors, for example, during operation when the storage is fully
charged; when the collectors are initially installed, before system start-up;
or when the system is shut down for maintenance or seasonal consider-
ations such as heating only systems in the summer.
4. Weathering Box Test Fixture
4.1 Weathering Box Test Fixture, consisting of a box, rails,
a box top, a glazing frame, and adhesive tapes. The weathering
box test fixture should be constructed in accordance with Figs.
1-5.
4.1.1 The box and box top should be made in metal that is
suitably resistant to corrosion encountered in the exposure
environment.Aweep hole should be drilled at the lower end of
the bottom of the box to provide drainage and to minimize
moisture accumulation.
NOTE 3—The box top is intended to protect the edges of the test
specimen in contact with the box from reaching excessively high
temperatures, to minimize exposure of the adhesive to sunlight, and to
minimize moisture penetration into the exposure test fixture.
4.1.2 The box interior shall be a flat black nonselective
NOTE 1—Make: 4 per box.
coating having an absorptance of not less than 0.90 after
NOTE 2—Material: metal suitably corrosion-resistant for exposure. A
exposure. Organic absorber coatings should be heated in an
typical material would be 24-gage galvanized steel.
oven at 150°C (302°F) for 24 h before the test fixture is 1
NOTE 3—Dimension tolerance 61mm(6 ⁄16 in.).
asssembled. This should minimize outgassing, which results
FIG. 2 Natural Weathering Box—Rolls
NOTE 1—Make: 1 per box.
NOTE 2—Material: metal suit
...

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4.1 The design of a photovoltaic module or system intended to provide safe conversion of the sun's radiant energy into useful electricity must take into consideration the possibility of partial shadowing of the module(s) during operation. This test method describes a procedure for verifying that the design and construction of the module provides adequate protection against the potential harmful effects of hot spots during normal installation and use.  
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4.4 Fig. 1 illustrates the hot spot effect in a module of a series string of cells, one of which, cell Y, is partially shadowed. The amount of electrical power dissipated in Y is equal to the product of the module current and the reverse voltage developed across Y. For any irradiance level, when the reverse voltage across Y is equal to the voltage generated by the remaining (s-1) cells in the module, power dissipation is at a maximum when the module is short-circuited. This is shown in Fig. 1 by the shaded rectangle constructed at the intersection of the reverse I-V characteristic of Y with the image of the forward I-V characteristic of the (s-1) cells.
FIG. 1 Hot Spot Effect  
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FIG. 2 Bypass Diode Effect  
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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.  
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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...
SCOPE
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.  
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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
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...
SCOPE
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
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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