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ASTM E2481-06

(Test Method)

Standard Test Method for Hot Spot Protection Testing of Photovoltaic Modules

Standard Test Method for Hot Spot Protection Testing of Photovoltaic Modules

SCOPE
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 non-uniform) 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.
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-2006
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

Replaced By
ASTM E2481-08 - Standard Test Method for Hot Spot Protection Testing of Photovoltaic Modules
Effective Date
01-Nov-2008
Referred By
ASTM E2908-12(2023) - Standard Guide for Fire Prevention for Photovoltaic Panels, Modules, and Systems
Effective Date
01-Mar-2006

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ASTM E2481-06 - Standard Test Method for Hot Spot Protection Testing of Photovoltaic ModulesASTM E2481-06 - Standard Test Method for Hot Spot Protection Testing of Photovoltaic Modules
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ASTM E2481-06 - Standard Test Method for Hot Spot Protection Testing of Photovoltaic Modules
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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:E2481–06
Standard Test Method for
Hot Spot Protection Testing of Photovoltaic Modules
This standard is issued under the fixed designation E 2481; 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.
1. Scope E 1799 Practice for Visual Inspections of Photovoltaic
Modules
1.1 This test method provides a procedure to determine the
E 1802 Test Methods forWet Insulation IntegrityTesting of
ability of a photovoltaic (PV) module to endure the long-term
Photovoltaic Modules
effects of periodic “hot spot” heating associated with common
fault conditions such as severely cracked or mismatched cells,
3. Terminology
single-point open circuit failures (for example, interconnect
3.1 Definitions—definitions of terms used in this test
failures), partial (or non-uniform) shadowing or soiling. Such
method may be found in Terminology E 772 and Terminology
effects typically include solder melting or deterioration of the
E 1328.
encapsulation, but in severe cases could progress to combus-
3.2 Definitions of Terms Specific to This Standard:
tion of the PV module and surrounding materials.
3.2.1 hot spot—aconditionthatoccurs,usuallyasaresultof
1.2 There are two ways that cells can cause a hot spot
shadowing, when a solar cell or group of cells is forced into
problem; either by having a high resistance so that there is a
reverse bias and must dissipate power, which can result in
large resistance in the circuit, or by having a low resistance
abnormally high cell temperatures.
area (shunt) such that there is a high-current flow in a localized
region. This test method selects cells of both types to be
4. Significance and Use
stressed.
4.1 The design of a photovoltaic module or system intended
1.3 This test method does not establish pass or fail levels.
to provide safe conversion of the sun’s radiant energy into
The determination of acceptable or unacceptable results is
useful electricity must take into consideration the possibility of
beyond the scope of this test method.
partial shadowing of the module(s) during operation. This test
1.4 This standard does not purport to address all of the
method describes a procedure for verifying that the design and
safety concerns, if any, associated with its use. It is the
construction of the module provides adequate protection
responsibility of the user of this standard to establish appro-
against the potential harmful effects of hot spots during normal
priate safety and health practices and determine the applica-
installation and use.
bility of regulatory limitations prior to use.
4.2 This test method describes a procedure for determining
2. Referenced Documents the ability of the module to provide protection from internal
2 defects which could cause loss of electrical insulation or
2.1 ASTM Standards:
combustion hazards.
E 772 Terminology Relating to Solar Energy Conversion
4.3 Hot-spot heating occurs in a module when its operating
E 927 Specification for Solar Simulation for Photovoltaic
current exceeds the reduced short-circuit current (Isc) of a
Testing
shadowed or faulty cell or group of cells. When such a
E 1036 Test Methods for Electrical Performance of Non-
condition occurs, the affected cell or group of cells is forced
concentrator Terrestrial Photovoltaic Modules and Arrays
into reverse bias and must dissipate power, which can cause
Using Reference Cells
overheating.
E 1328 Terminology Relating to Photovoltaic Solar Energy
Conversion
NOTE 1—The correct use of bypass diodes can prevent hot spot damage
from occurring.
4.4 Fig. 1 illustrates the hot-spot effect in a module of a
This test method is under the jurisdiction of ASTM Committee E44 on Solar,
series string of cells, one of which, cell Y, is partially
Geothermal and Other Alternative Energy and is the direct responsibility of
shadowed. The amount of electrical power dissipated in Y is
Subcommittee E44.09 on Photovoltaic Electric Power Conversion.
Current edition approved March 1, 2006. Published March 2006.
equal to the product of the module current and the reverse
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
voltage developed across Y. For any irradiance level, when the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
reversevoltageacross Yisequaltothevoltagegeneratedbythe
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. remaining (s-1) cells in the module, power dissipation is at a
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2481–06
FIG. 1 Hot Spot Effect
maximum when the module is short-circuited.This is shown in 4.6.1.2 Oftenlowshuntresistancecellsarethiswaybecause
Fig. 1 by the shaded rectangle constructed at the intersection of oflocalizedshunts.Inthiscasehotspotheatingoccursbecause
the reverse I-V characteristic of Y with the image of the a large amount of current flows in a small area. Because this is
forward I-V characteristic of the (s-1) cells. a localized phenomenon, there is a great deal of scatter in
4.5 By-pass diodes, if present, as shown in Fig. 2, begin performance of this type of cell. Cells with the lowest shunt
conducting when a series-connected string in a module is in resistance have a high likelihood of operating at excessively
reverse bias, thereby limiting the power dissipation in the high temperatures when reverse biased.
reduced-output cell.
4.6.1.3 Because the heating is localized, hot spot failures of
low shunt resistance cells occur quickly.
NOTE 2—If the module does not contain bypass diodes, check the
manufacturer’sinstructionstoseeifamaximumnumberofseriesmodules 4.6.2 High Shunt Resistance Cells:
is recommended before installing bypass diodes. If the maximum number
4.6.2.1 The worst case shadowing conditions occur when a
of modules recommended is greater than one, the hot spot test should be
small fraction of the cell is shadowed.
preformed with that number of modules in series. For convenience, a
4.6.2.2 High shunt resistance cells limit the reverse current
constant current power supply may be substituted for the additional
modules to maintain the specified current. flow of the circuit and therefore heat up. The cell with the
highest shunt resistance will have the highest power dissipa-
4.6 The reverse characteristics of solar cells can vary
tion.
considerably. Cells can have either high shunt resistance where
4.6.2.3 Because the heating is uniform over the whole area
the reverse performance is voltage-limited or have low shunt
of the cell, it can take a long time for the cell to heat to the
resistance where the reverse performance is current-limited.
point of causing damage.
Each of these types of cells can suffer hot spot problems, but in
different ways. 4.6.2.4 High shunt resistance cells define the need for
4.6.1 Low-Shunt Resistance Cells: bypass diodes in the module’s circuit, and their performance
4.6.1.1 The worst case shadowing conditions occur when characteristics determine the number of cells that can be
the whole cell (or a large fraction) is shadowed. protected by each diode.
FIG. 2 Bypass Diode Effect
E2481–06
4.7 The major technical i
...

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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.  
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SCOPE
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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 E744-07(2022)(Practice)
Standard Practice for Evaluating Solar Absorptive Materials for Thermal Applications

SIGNIFICANCE AND USE
4.1 The methods in this practice are intended to aid in the assessment of long-term performance by comparative testing of absorptive materials. The results of the methods, however, have not been shown to correlate to actual in-service performance.  
4.2 The testing methodology in this practice provides two testing methods, in accordance with Fig. 1.
FIG. 1 Outline of Test Method Options  
4.2.1 Method A, which aims at decreasing the time required for evaluation, uses a series of individual tests to simulate various exposure conditions.  
4.2.2 Method B utilizes a single test of actual outdoor exposure under conditions simulating thermal stagnation.  
4.2.3 Equivalency of the two methods has not yet been established.
SCOPE
1.1 This practice covers a testing methodology for evaluating absorptive materials used in flat plate or concentrating collectors, with concentrating ratios not to exceed five, for solar thermal applications. This practice is not intended to be used for the evaluation of absorptive surfaces that are (1) used in direct contact with, or suspended in, a heat-transfer liquid, (that is, trickle collectors, direct absorption fluids, etc.); (2) used in evacuated collectors; or (3) used in collectors without cover plate(s).  
1.2 Test methods included in this practice are property measurement tests and aging tests. Property measurement tests provide for the determination of various properties of absorptive materials, for example, absorptance, emittance, and appearance. Aging tests provide for exposure of absorptive materials to environments that may induce changes in the properties of test specimens. Measuring properties before and after an aging test provides a means of determining the effect of the exposure.  
1.3 The assumption is made that solar radiation, elevated temperature, temperature cycles, and moisture are the primary factors that cause degradation of absorptive materials. Aging tests are described for exposure of specimens to these factors.  
Note 1: For some geographic locations, other factors, such as salt spray and dust erosion, may be important. They are not evaluated by this practice.  
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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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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