Definition
PID (Potential Induced Degradation) is a leakage-current-driven loss of PV module performance caused by high-voltage stress between cells and grounded frame. Manifests as 20–50% power loss within months in unmanaged systems.
PID Mechanism
- High voltage between cells and grounded frame.
- Humidity + heat enable ion migration through encapsulant.
- Ions accumulate at cell-glass interface.
- Shunt resistance decreases → Pmax drops.
- Voc drops; FF drops.
Prevention
- PID-free / PID-resistant modules: certified per IEC 62804.
- Recovery systems: nightly reverse-voltage application (some inverters).
- Grounding strategy: PID-N (negative ground).
- Encapsulant quality: high-quality EVA, POE backsheets.
Detection
- IR thermography during operation.
- I-V curve tracing.
- Power output monitoring (sudden drops).
Key Takeaways
- PID = leakage-current-driven module degradation.
- Can cause 20–50% power loss in months on unmanaged systems.
- TOPCon and HJT more PID-resistant than PERC.
- Specify PID-resistant modules per IEC 62804.
- Use PID-recovery systems on long strings in humid/hot climates.
Frequently Asked Questions
5 commonly searched questions about PID (Potential Induced Degradation).
What is PID?
Potential Induced Degradation — leakage current between cells and the grounded module frame causes ion migration and shunting in PV cells, reducing power output 20–50% in months.
What causes PID?
High voltage between cells (typical in long strings) + grounded frame + humidity + heat. Most common at the bottom modules of long strings where voltage to ground is highest.
How is PID prevented?
PID-resistant modules (passivated cells, EVA quality). PID recovery systems (some inverters apply reverse voltage at night). Grounding the negative terminal (PID-N). Use of PID-tested modules.
Are TOPCon and HJT susceptible?
TOPCon: lower susceptibility than PERC. HJT: very low susceptibility (different cell architecture). Both better than PERC for PID resistance.
Is PID covered by warranty?
Yes — module manufacturer power warranty includes PID. But field-detected PID may require IR thermography to document, and warranty claims process is lengthy.
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