Correlating Infrared Thermography With Electrical Degradation of PV Modules Inspected in All-India Survey of Photovoltaic Module Reliability 2016

Degradation in electrical performance of photovoltaic (PV) modules is related to the degradation of the solar cells and laminate materials in the modules, which often shows up as hot spots in infrared (IR) thermography. The analysis of the IR data of crystalline silicon modules inspected in the field during the All India Survey of Photovoltaic Module Reliability in 2016 is being presented in this paper, along with its correlation to the electrical degradation in these modules. The thermal mismatch in the PV modules has been quantified in terms of a Thermal Mismatch Index, based on the difference between the highest cell temperature and the representative module temperature. Modules with high thermal mismatch (hot cells) under MPPT condition show high power degradation, caused mainly due to fill factor degradation. Modules with hot cells show higher degradation in "Hot" climatic zones as compared with "Non-Hot" climates. The analysis indicates that modules having cracks and hot cells have higher power degradation than modules having cracks but no hot cells. This indicates that the worst cracks tend to create hot cells in the modules, while the benign cracks (which have lesser impact on power output) do not affect the cell temperature to that extent.