The “EN IEC 62716 Photovoltaic (PV) modules - Ammonia corrosion test” standard, which is based on a European standard and later published by the International Electrotechnical Commission (IEC) , describes useful test methods for determining the resistance of photovoltaic (PV) modules to ammonia. Except for the bypass diode functionality test, the details of all tests are included in the following standards:
These test methods are combined in this standard to provide tools for evaluating potential failures in photovoltaic (PV) modules when operating in wet atmospheres containing high levels of dissolved ammonia.
This standard applies to flat plate photovoltaic (PV) modules. The structure of this standard closely follows the standard “IEC 61701 Photovoltaic (PV) modules - Salt fog corrosion test”.
Three identical samples of the photovoltaic (PV) module or assembly of interest are subjected to any of the test sequences given in the figures given in the standard, depending on the photovoltaic (PV) technology considered, i.e. crystalline silicon or thin film respectively. As the figures show, one of these samples shall be used as a control. The control sample shall be used as a control each time the test samples are measured to assess the effect of the ammonia exposure test.
If a full-size sample is too large to fit into the enclosures required for ammonia exposure testing, a smaller, representative sample may be specially designed and manufactured for this test. The representative sample should be carefully designed to reveal similar failure mechanisms to the full-size sample, and the manufacturing process for the representative sample should be as identical as possible to that of the full-size sample. The fact that the test was performed on representative samples and not on full-size samples should be stated in the test report. If the photovoltaic (PV) module is equipped with grounding devices, these form part of the test sample.
The test results relate only to the tested sample structure. If a module manufacturer uses several sources for photovoltaic module components, additional test samples are required. The samples should be selected so that each encapsulation material used in the product range and any components forming the module's outer surface are represented.
All tests in the figures, except the bypass diode functionality test, are fully described in the IEC standards from which the specific tests are taken. The tests in these figures should be performed in the order specified. Any changes or deviations should be recorded and reported in detail.
The purpose of the bypass diode functionality test is to verify that the bypass diode or diodes of the test samples remain functional after exposure to ammonia. In the case of modules without bypass diodes, this test can be skipped.
This procedure can be performed in any environment of 25 degrees plus/minus 10 degrees. The sample should not be exposed to illumination during the test. Electrically short-circuit all blocking diodes included in the test sample. The nominal short-circuit current of the test sample is determined from its label or instruction sheet. The positive output of the DC power supply is connected to the negative terminals of the test sample and the negative output of the DC power supply is connected to the positive terminals of the test sample using the manufacturer's minimum recommended wire gauge. The manufacturer's recommendations for wire entry into the wiring compartment are followed. In this configuration, current should flow in the reverse direction through the cells and forward through the diodes. In modules with overlapping bypass diode circuits, a jumper cable may be installed to ensure that all current flows through a bypass diode. A current equal to 1,25 times the short-circuit current of the test sample (plus7-minus 5 percent) is applied for 1 hour.
After 1 hour of current flow, it is checked that the bypass diodes remain operational. One possible method is to pass reverse current through the cells, then forward current through the diodes, and then monitor the temperature of the diodes with the help of a thermal IR camera. The diodes should reach thermal equilibrium with the environment after the last step above before applying this procedure. Another option is to shade a solar cell protected by each diode in the PV module and verify the characteristics of the resulting curve (under illumination close to standard test conditions) to check whether the bypass diodes are operational.
All test samples are preconditioned with global or direct normal sunlight (natural or simulated) according to the specifications given in the design qualification and type approval IEC standard applicable to the PV module technology in question.
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