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Potential- Induced Degradation

Potential- Induced Degradation

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The PQP’s Potential Induced Degradation (PID) teest doubles the IEC/UL certification test duration to 192 hours. PID occurs primarily in electrically ungrounded PV systems with high voltages, especially those using transformerless inverters. There are multiple forms of PID, including PID-shunting and PID-polarity. PID-shunting occurs when sodium ions from the glass travel to pinholes in the anti-reflective coatings on the cells, permanently lowering performance. PID-polarity is static charge build-up due to internal circuit voltages, and is possibly reversible.

Key
Takeaways

Only 58% of BOMs tested degraded by < 2%.

This is a significant decrease from the 79% of BOMs reported in last year’s Scorecard. The median degradation following PID increased from 1.1% for BOMs produced in 2022 to 1.8% for BOMs produced in 2023, and the average degradation increased from 1.6% to 2.1%. See the Power Degradation graph below for more. See the Power Degradation graph below for more.

Test Result Spotlight

Potential induced degradation can take many forms, including PID-s (shunting), PID-c (corrosion), and PID-p (polarization). Recent PQP testing has revealed an increasing number of BOMs that are susceptible to PID-p, including the TOPCon module shown here. Kiwa PVEL’s testing has confirmed that many BOMs do not exhibit PID-p, but others can suffer a significant amount of power loss. While a subsequent short duration exposure to UV light can often reverse this effect, some research has shown examples of PID-p occurring in the field.

PRE-STRESS

Test Result Spotlight

The pre-stress image shows a perfect module with no EL anomalies.

PID192(-)

Test Result Spotlight

After 192 hours of PID(-) testing, most cell bus bars show an accumulation of polarization charges.

Power Degradation of PID BOMs

Power degradation chart for PID stress sequence

All 2013/2014 and 2015 results are from 600 hours of PID testing. This was decreased to 192 hours for 2016 results and beyond. Outliers with >10% degradation are not shown. In some cases, these cause a significant reduction in the mean.

View Box Plot Interpretation Guide

A case study on why PID is important, what PV module materials are assessed, and the test procedure can be found here on kiwa.com/pvel.

Kiwa PVEL Top Performer

See PID Top Performers

Click here to see the 145 model types listed as PID Top Performers.

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