Significance and Use

The useful life of photovoltaic modules may depend on their ability to withstand repeated temperature cycling with varying amounts of moisture in the air. These test methods provide procedures for simulating the effects of cyclic temperature and humidity environments. An extended duration damp heat procedure is provided to simulate the effects of long term exposure to high humidity.

The durations of the individual environmental tests are specified by use of this test method; however, commonly used durations are 50 and 200 thermal cycles, 10 humidity-freeze cycles, and 1000 h of damp heat exposure, as specified by module qualification standards such as IEC 61215 and IEC 61646. Longer durations can also be specified for extended duration module stress testing.

Mounting Test modules are mounted so that they are electrically isolated from each other, and in such a manner to allow free air circulation around the front and back surfaces of the modules.

Current Biasing :

During the thermal cycling procedure, test modules are operated without illumination and with a forward-bias current equal to the maximum power point current at standard reporting conditions (SRC, see Test Methods E 1036 ) flowing through the module circuitry.

The current biasing is intended to stress the module interconnections and solder bonds in ways similar to those that are believed to be responsible for fill-factor degradation in field-deployed modules.

Effects of Test Procedures Data generated using these test methods may be used to evaluate and compare the effects of simulated environment on test specimens. These test methods require determination of both visible effects and electrical performance effects.

Effects on modules may vary from none to significant changes. Some physical changes in the module may be visible when there are no apparent electrical changes in the module. Similarly, electrical changes may occur with no visible changes in the module.

All conditions of measurement, effects of cycling, and any deviations from this test method must be described in the report so that an assessment of their significance can be made.

Sequencing If these test methods are performed as part of a combined sequence with other environmental or non-environmental tests, the results of the final electrical tests (6.2) and visual inspection (6.3) determined at the end of one test may be used as the initial electrical tests and visual inspection for the next test; duplication of these tests is not necessary unless so specified.

1. Scope

1.1 These test methods provide procedures for stressing photovoltaic modules in simulated temperature and humidity environments. Environmental testing is used to simulate aging of module materials on an accelerated basis.

1.2 Three individual environmental test procedures are defined by these test methods: a thermal cycling procedure, a humidity-freeze cycling procedure, and an extended duration damp heat procedure. Electrical biasing is utilized during the thermal cycling procedure to simulate stresses that are known to occur in field-deployed modules.

1.3 These test methods define mounting methods for modules undergoing environmental testing, and specify parameters that must be recorded and reported.

1.4 These test methods do not establish pass or fail levels. The determination of acceptable or unacceptable results is beyond the scope of these test methods.

1.5 Any of the individual environmental tests may be performed singly, or may be combined into a test sequence with other environmental or non-environmental tests, or both. Certain pre-conditioning tests such as annealing or light soaking may also be necessary or desirable as part of such a sequence. The determination of any such sequencing and pre-conditioning is beyond the scope of this test method.

1.6 These test procedures are limited in duration and therefore the results of these tests cannot be used to determine photovoltaic module lifetimes.

1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

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

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

E772 Terminology of Solar Energy Conversion

E1036 Test Methods for Electrical Performance of Nonconcentrator Terrestrial Photovoltaic Modules and Arrays Using Reference Cells

E1328 Terminology Relating to Photovoltaic Solar Energy Conversion

E1462 Test Methods for Insulation Integrity and Ground Path Continuity of Photovoltaic Modules

E1799 Practice for Visual Inspections of Photovoltaic Modules

Keywords

damp heat exposure; environmental testing; humidity-freeze cycling; modules; photovoltaics; solar energy; thermal cycling; Electrical performance--solar devices; Temperature tests--solar devices/applications; Visual examination--solar devices; Cycling; Defects; Degradation; Ground path continuity; Hi-pot test; Humidity; Instrumental measurement; Moisture analysis; Anomalies; Photovoltaic (PV) power systems; Solar collectors; Thermal cycling test;

ICS Code

ICS Number Code 27.160 (Solar energy engineering)

DOI: 10.1520/E1171-09

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ASTM E1171