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ASTM E781-86(2015)

(Practice)

Standard Practice for Evaluating Absorptive Solar Receiver Materials When Exposed to Conditions Simulating Stagnation in Solar Collectors With Cover Plates

Standard Practice for Evaluating Absorptive Solar Receiver Materials When<brk/> Exposed to Conditions Simulating Stagnation in Solar<brk/> 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 modelling 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 11874).  
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 Absor...
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 nonoperational 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

Status
Historical
Publication Date
28-Feb-2015
ICS
27.160 - Solar energy engineering
Technical Committee
E44 - Solar, Geothermal and Other Alternative Energy Sources
Drafting Committee
E44.20 - Optical Materials for Solar Applications
Current Stage
Ref Project

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ASTM E781-86(2015) - Standard Practice for Evaluating Absorptive Solar Receiver Materials When<brk/> Exposed to Conditions Simulating Stagnation in Solar<brk/> Collectors With Cover PlatesASTM E781-86(2015) - Standard Practice for Evaluating Absorptive Solar Receiver Materials When<brk/> Exposed to Conditions Simulating Stagnation in Solar<brk/> Collectors With Cover Plates
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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: E781 − 86 (Reapproved 2015)
Standard Practice for
Evaluating Absorptive Solar Receiver Materials When
Exposed to Conditions Simulating Stagnation in Solar
1
Collectors with Cover Plates
This standard is issued under the fixed designation E781; 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.
3
1. Scope D1898 Practice for Sampling of Plastics (Withdrawn 1998)
E408 Test Methods for Total Normal Emittance of Surfaces
1.1 This practice covers a test procedure for evaluating
Using Inspection-Meter Techniques
absorptive solar receiver materials and coatings when exposed
E434 Test Method for Calorimetric Determination of Hemi-
to sunlight under cover plate(s) for long durations. This
spherical Emittance and the Ratio of Solar Absorptance to
practice is intended to evaluate the exposure resistance of
Hemispherical Emittance Using Solar Simulation
absorber materials and coatings used in flat-plate collectors
E772 Terminology of Solar Energy Conversion
where maximum nonoperational stagnation temperatures will
E903 Test Method for Solar Absorptance, Reflectance, and
be approximately 200°C (392°F).
Transmittance of Materials Using Integrating Spheres
1.2 This practice shall not apply to receiver materials used
E962
in solar collectors without covers (unglazed) or in evacuated
collectors, that is, those that use a vacuum to suppress
3. Terminology
convective and conductive thermal losses.
3.1 Definitions:
1.3 The values stated in SI units are to be regarded as the
3.1.1 See Terminology E772 for definitions.
standard.
4. Significance and Use
1.4 This standard does not purport to address all of the
4.1 Although this practice is intended for evaluating solar
safety concerns, if any, associated with its use. It is the
absorber materials and coatings used in flat-plate collectors, no
responsibility of the user of this standard to establish appro-
single procedure can duplicate the wide range of temperatures
priate safety, health, and environmental practices and deter-
and environmental conditions to which these materials may be
mine the applicability of regulatory limitations prior to use.
exposed during in-service conditions.
1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
4.2 This practice is intended as a screening test for absorber
ization established in the Decision on Principles for the
materials and coatings. All conditions are chosen to be repre-
Development of International Standards, Guides and Recom-
sentative of those encountered in solar collectors with single
mendations issued by the World Trade Organization Technical
cover plates and with no added means of limiting the tempera-
Barriers to Trade (TBT) Committee.
ture during stagnation conditions.
4.3 This practice uses exposure in a simulated collector with
2. Referenced Documents
a single cover plate. Although collectors with additional cover
2
2.1 ASTM Standards:
plates will produce higher temperatures at stagnation, this
B537 Practice for Rating of Electroplated Panels Subjected
procedure is considered to provide adequate thermal testing for
to Atmospheric Exposure
most applications.
NOTE 1—Mathematical modelling has shown that a selective absorber,
single glazed flat-plate solar collector can attain absorber plate stagnation
1
This practice is under the jurisdiction of ASTM Committee E44 on Solar,
temperatures as high as 226°C (437°F) with an ambient temperature of
Geothermal and Other Alternative Energy Sources and is the direct responsibility of
37.8°C (100°F) and zero wind velocity; and a double glazed one as high
Subcommittee E44.20 on Optical Materials for Solar Applications.
as 245°C (482°F) under these conditions. The same configuration solar
Current edition approved March 1, 2015. Published April 2015. Originally
collector with a nonselective absorber can attain absorber stagnation
approved in 1981. Last previous edition approved in 2009 as E781 – 86 (2009).
temperatures as high as 146°C (284°F), if single glazed, and 185°C
DOI: 10.1520/E0781-86R15.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
3
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
E781 − 8
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E781 − 86 (Reapproved 2009) E781 − 86 (Reapproved 2015)
Standard Practice for
Evaluating Absorptive Solar Receiver Materials When
Exposed to Conditions Simulating Stagnation in Solar
1
Collectors With Cover Plates
This standard is issued under the fixed designation E781; 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
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 nonoperational 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
B537 Practice for Rating of Electroplated Panels Subjected to Atmospheric Exposure
3
D1898 Practice for Sampling of Plastics (Withdrawn 1998)
E408 Test Methods for Total Normal Emittance of Surfaces Using Inspection-Meter Techniques
E434 Test Method for Calorimetric Determination of Hemispherical Emittance and the Ratio of Solar Absorptance to
Hemispherical Emittance Using Solar Simulation
E772 Terminology of Solar Energy Conversion
E903 Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres
E962
3. Terminology
3.1 Definitions:
3.1.1 See Terminology E772 for definitions.
4. 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.
1
This practice is under the jurisdiction of ASTM Committee E44 on Solar, Geothermal and Other Alternative Energy Sources and is the direct responsibility of
Subcommittee E44.05 on Solar Heating and Cooling Systems and Materials.
Current edition approved April 1, 2009March 1, 2015. Published June 2009April 2015. Originally approved in 1981. Last previous edition approved in 20032009 as
E781–86(2003).E781–86(2009). DOI: 10.1520/E0781-86R09.10.1520/E0781-86R15.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 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 the ASTM website.
3
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
E781 − 86 (2015)
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 modelling 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 gla
...

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FIG. 2 Bypass Diode Effect  
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1.1 This test method provides measurement and analysis procedures for determining the capacity of a specific photovoltaic system built in a particular place and in operation under natural sunlight.  
1.2 This test method is used for the following purposes:  
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1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.9 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...

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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.  
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 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
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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