PV

If two or more samples fail any of the test criteria detailed in the applicable standard, the design is deemed to fail qualification. Should one sample fail any test, another two samples undergo the relevant test sequence from the beginning. If one or both of these new samples also fail, the design is deemed to fail qualification requirements. If both samples pass the test sequence, the design is deemed to meet qualification requirements.

Figure: Testing Sequence according to IEC 61215







Figure: Testing Sequence according to IEC 61646

Bypass Diode Thermal Test

The bypass diode test is a thermal test that determines the thermal behaviour of the PV module when placed in a hot-spot condition simulation. This would test the reliability of the PV modules in operation at the collection site.

The test methodology is conducted through attaching a thermocouple to the diode body, heating the module up to 75°C + 5°C, and applying a current equal to the short circuit current measured at standard test conditions for one hour. The temperature of each bypass diode body is measured, and the junction temperature is calculated using a formula derived from the specifications provided by the diode's manufacturer. The current is then increased to 1.25 times the short-circuit current of the module, as measured at standard test conditions for another hour while maintaining the module temperature at the same temperature.

To pass, the diode should still be operational following the test.

Damp Heat Test

The damp-heat test is an environmental test carried out for 1000 hours that is designed to determine the ability of the PV module to withstand long-term exposure to the penetration of humidity by applying 85°C ± 2°C with a relative humidity of 85 percent ± 5 percent for 1,000 hours.

One of the challenges faced by the PV modules is the process of protection from humidity through edge sealing in the lamination process. Humidity penetration results in delamination and the corrosion of cell parts. Even if no major defects are detected after damp heat test, the module would be in a state where it has been stressed to the point that it becomes "fragile" for the subsequent mechanical load test.

Hail Test

The hail impact test is a mechanical test that is designed to determine if the PV module is capable of withstanding the impact of hailstones at a temperature of ~ –4°C. The test equipment consists of a unique launcher, capable of propelling various weights of ice balls at specified velocities, so as to hit the module at 11 specified impact locations.

Figure: Ice-ball masses and test velocities

After the test, there should be no major defects caused by the hailstones.

Humidity Freezing Test

The humidity-freeze test is an environmental test verifies the module's ability to withstand the effects of high temperatures and humidity, immediately followed by extremely low temperatures. The test consists of 10 complete cycles that the module is subjected to. A harmonized profile of the humidity-freeze test is illustrated below:

Harmonized profile for the humidity-freeze test

After this test, the module is allowed to rest between two and four hours before the visual inspection, and before maximum output power and insulation resistance are measured.

Mechanical Loading Test

This loading test verifies the PV module’s ability to withstand wind, snow, static, or ice loads. The Mechanical load testing is carried out after damp heat testing and is performed on a sample that has undergone severe environmental stress.

A most critical aspect of the mechanical loading test is associated to the mounting of the module according to mounting instructions of the manufacturer. Proper care must be taken in regards to mounting. When failures happen, the test must be free of doubts of whether the failure is due to actual structural problems or inappropriate mounting techniques.

2,400 Pa is first applied (which simulates a 130km/hr wind pressure) for 1 hour on each face of the module. If the test requires that the module also withstand the accumulations of ice and snow, the load applied to the front of the module is then further increased from 2,400 Pa to 5,400 Pa. When the test concludes, there should be no major visual defects and no intermittent open-circuits detected during the test.

Robustness of Termination Test

The Robustness of Termination Test is a mechanical test that reflects the robustness of the PV modules and its components. The PV module’s terminations will be put through a stress test would reflect the amount of tensile strength, bending and torque exerted in the processes of normal assembly and handling as referenced in IEC 60068-2-21. This ensures its ability to withstand the stress applied to the modules during its installation or during operations.

The robustness of termination test complies with international test standards of IEC 61216 “Crystalline silicon terrestrial photovoltaic (PV) modules – Design qualification and type approval” and IEC 61646 “Thin-film terrestrial photovoltaic (PV) modules – Design qualification and type approval.”

Temperature Cycling Test

The thermal cycling test for 200 cycles (TC200) is an environmental test that simulates the thermal stresses placed on materials due to changes of extreme temperatures. The most common challenges are faced by soldered connections within the laminate due to the different thermal expansion coefficients of the various encapsulated materials. This may result in failure for major defects, Pmax degradation, or interruption of the electric circuitry.

Part of the requirements of IEC 61215 is having a current pass through with a ±2 percent of the current measured at peak power when the module temperature is above 25°C. IEC 61646 does not specifically mention this current injection, but this is done so to observe the continuity of the electrical circuit. The module is subjected to the cycling temperature limits of –40°C ± 2°C and +85°C ± 2°C with the profile shown in figure 3.

Cycling temperature limits of the TC200 test

Wet Leakage Current Test

The wet leakage is also an electrical safety test used to evaluate the insulation of the module against moisture penetration under wet operating conditions such as rain, fog, dew, melted snow to avoid corrosion, ground fault and electrical shock hazard.

The module is submersed in a shallow tank to a depth covering all surfaces, including mating connectors, but not cable entries of junction boxes not designed for immersion. A test voltage is applied between the shorted output connectors and the water bath solution, up to the maximum system voltage of the module, for two minutes. The insulation resistance should not be less than 40MΩ for every square meter for modules with an area larger than 0.1m².