ABOUT “ PID“
During Early Stages of Solar industry , There have been reports from field that the module’s power out is going down drastically after few months into operation. The sudden drop in the power output particularly in power projects is attributed to a phenomenon called “ Potential Induced Degradation ( PID )” . Researchers from Solon and Fraunhofer etc., have found that due to improper grounding at Transformerless ( TL ) inverters, certain charge remains in the panels causing the Ion migration from the glass thru EVA to cells and Frame.
What is Potential Induced Degradation:
- Voltage (Potential) aging mechanism of modules which leads to decrease of PV module power.
Modules Exhibit Loss of Power Output due to:
- Polarization of the cell surface
- Polarization changes at the semi-conductive junction
PID Contributing Factors
- Sodium and potassium ion movement from glass towards cell
- Negative bias accelerates more than positive bias
- Temperature ( Hot places )
- Moisture ( Thru back sheet )
- Encapsulant properties ( EVA formulations )
- Modules with ground of cells to frame ground do not exhibit PID
- Reverse bias overnight can help to reduce the effect
- Use of PID resistant materials
Electro Luminance image of local panels before and after 100hr of 1000 V PID test – Power loss was 32%
Electro Luminance image of Sunfuel’s panels before and after 100hr of 1000 V PID test – Power loss was nil.