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ASTM E904-87(2001)

(Practice)

Standard Practice for Generating All-Day Thermal Performance Data for Solar Collectors

Standard Practice for Generating All-Day Thermal Performance Data for Solar Collectors

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1.1 This practice provides a means of generating all-day thermal performance data for flat-plate collectors, concentrating collectors, and tracking collectors.  
1.2 The values stated in SI units are to be regarded as the standard. The values given in the parentheses are for information only.  
1.3 This standard does not purport to address all of the safety problems, 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
30-Jul-1987
ICS
27.160 - Solar energy engineering
Technical Committee
E44 - Solar, Geothermal and Other Alternative Energy Sources
Current Stage
Ref Project

Relations

Replaces
ASTM E904-87(1995) - Standard Practice for Generating All-Day Thermal Performance Data for Solar Collectors
Effective Date
31-Jul-1987
Replaced By
ASTM E904-87(2007) - Standard Practice for Generating All-Day Thermal Performance Data for Solar Collectors (Withdrawn 2013)
Effective Date
01-Mar-2007

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ASTM E904-87(2001) - Standard Practice for Generating All-Day Thermal Performance Data for Solar CollectorsASTM E904-87(2001) - Standard Practice for Generating All-Day Thermal Performance Data for Solar Collectors
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ASTM E904-87(2001) - Standard Practice for Generating All-Day Thermal Performance Data for Solar Collectors
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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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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:E904–87(Reapproved2001)
Standard Practice for
Generating All-Day Thermal Performance Data for Solar
Collectors
This standard is issued under the fixed designation E 904; 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 (e) indicates an editorial change since the last revision or reapproval.
NOTE 1—For concentrating collectors, the gross aperature area includes
1. Scope
anyareaofthereflectororrefractorshadedbythereceiveranditssupports
1.1 This practice covers a means of generating all-day
and including gaps between reflector segments within a collector module.
thermal performance data for flat-plate collectors, concentrat-
Net aperture excludes any shaded area or gaps between reflector segments
ing collectors, and tracking collectors.
and is sometimes called effective aperture area.
1.2 The values stated in SI units are to be regarded as the
(E 772)
standard. The values given in the parentheses are for informa-
3.1.4 heat transfer fluid, n—in solar energy systems, (1)
tion only.
liquid or gas that passes through the solar collector and carries
1.3 This standard does not purport to address all of the
the absorbed thermal energy away from the collector. (2) any
safety concerns, if any, associated with its use. It is the
fluid that is used to transfer thermal energy between sub-
responsibility of the user of this standard to establish appro-
systems in solar energy systems. (E 772)
priate safety and health practices and determine the applica-
3.1.5 non-operational mode exposure, n—condition that
bility of regulatory limitations prior to use.
exists when the collector has been filled, then purged of heat
transferfluid(ifaliquid)andcapped(butnotsealed)toprevent
2. Referenced Documents
introduction of foreign substances, mounted on a test rack, and
2.1 ASTM Standards:
exposed to solar radiation. (E 772)
E 772 Terminology Relating to Solar Energy Conversion
3.1.6 stagnation conditions, n—conditions(thatis,tempera-
2.2 ASHRAE Standards:
ture and pressure) existing when an energy system has attained
93-86 Methods ofTesting to Determine theThermal Perfor-
a quasi-steady state after the flow of heat transfer fluid has
mance of Solar Collectors
stopped, but the absorber continues to receive significant solar
96-80 Methods ofTesting to Determine theThermal Perfor-
irradiance. (E 772)
mance of Unglazed Flat-Plate Liquid-Type Solar Collec-
3.1.7 tilt angle, n—in solar energy applications, angle
tors
between the horizontal and the plane of the detector (collector,
photovoltaic array, instrument) surface. (E 772)
3. Terminology
3.1.8 time constant, n—time required for the temperature
3.1 Definitions:
change in the fluid leaving a solar collector to attain 63.2 % of
3.1.1 Terms from Terminology E 772 and solar nomencla-
its equilibrium value following a step change in the solar
ture documents under ballot, are listed for convenience.
irradiance or inlet fluid temperature.
3.1.2 For definitions of other terms used in this practice,
refer to Terminology E 772. NOTE 2—The step change involved should be thoroughly described in
the procedure.
3.1.3 area, aperture, n—of a solar thermal collector, maxi-
mum projected area through which the unconcentrated solar
3.2 Definitions of Terms Specific to This Standard:
radiant energy is admitted, measured in square metres (m )
3.2.1 useful energy (removed), n—time integral of the
(square feet (ft )).
product of mass flow rate, specific heat, and temperature
difference across the collector when the outlet temperature is
greater than the inlet temperature.
This practice is under the jurisdiction of ASTM Committee E44 on Solar,
Geothermal, and otherAlternative Energy Sources and is the direct responsibility of
4. Summary of Practice
Subcommittee E44.05 on Solar Heating and Cooling Subsystems and Systems.
Current edition approved July 31, 1987. Published December 1987. Originally
4.1 The solar collector is mounted in accordance with the
published as E 904 – 82. Last previous edition E 904 – 82.
manufacturer’s instructions. A constant flow rate and inlet
Annual Book of ASTM Standards, Vol 12.02.
Available from the American Society of Heating, Refrigeration, and Air- temperature, and the transfer fluid, is preselected and specified.
conditioning Engineers, Inc. (ASHRAE), Publications Sales Department, 1791
The temperature, fluid flow rate, irradiance, and wind param-
Tullie Circle, N.E.Atlanta, GA30329; orAmerican National Standards Institute, 11
eters are recorded throughout the daylight hours. Data are
W. 42nd St., 13th Flr., New York, NY 10036, for the ANSI standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E904
collectedat1-minintervalsormorefrequently,andtheaverage 7.1.2 Time constant—Determine the collector time constant
values are reported for each 5-min interval of the test day. at the mass flow rate utilized in this test method and in
All-day thermal performance is determined from the summa- accordance with ASHRAE 93-86.
tion of energy outputs for all intervals of the test day.
7.2 Test Conditions:
7.2.1 Exposure Conditions—Precondition the solar collec-
5. Significance and Use
tors in accordance with Section 6.
5.1 This practice may be employed for a relative determi- 7.2.2 Operating Conditions—Pump the specified transfer
nation of the useful energy collected by different solar collec-
fluid through the collectors at a constant preselected mass flow
tors tested side-by-side under the same operating and environ- rate and inlet temperature specified by the manufacturer. The
mental parameters, in the same location, and on the same test selected flow rate should be the projected flow rate for the
day. Variations in inlet temperature and transfer fluid flow rate anticipated end-use application, and the inlet temperature
should be minimized for best results. should be selected to provide the anticipated end-use tempera-
5.2 Limitations: Caution should be exercised when com- ture. Maintain the inlet temperatures within6 0.5°C (6 1°F)
paring the all-day thermal performance data for collectors during each 5-min measurement interval and within 6 2.5°C
tested by this practice to the performance of other collectors (6 5°F) during the test day. Maintain the flow rate within 6
not tested at the same time and the same location, or with the 1.0 % during each 5-min measurement interval. Variations in
same test conditions. The data collected by this practice inlet temperature and mass flow rate should be minimized for
represent the behavior of the tested colle
...

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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.  
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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 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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