Statistical analysis of 10+ years field exposed c-Si modules performance degradation

In our previous study1, visual inspections and infra-red (IR) scanning were performed on about 2,000 modules that have been operating under the dry and hot Arizona climate for 10 - 17 years. Most of these modules were installed on 1-axis trackers and grid-connected; and some were installed on a fixed latitude tilt rack in a standalone system. The modules were inspected against a list of historically known field failure modes, but restricted to those that could be visually observed or through IR. An analysis of the data revealed both positive and negative correlations between the failure modes. Failure chains could be constructed from those correlations; such as (1) Discoloration of encapsulant – cell discoloration, and (2) Delamination – broken/chipped cells. This study focuses on modules installed on 2-axis trackers between 8 and 13 years. Statistical degradation analysis is performed on power output data collected throughout the exposure period. The electroluminescence imaging and a more thorough IR scanning are performed on limited (available) samples to complement the visual inspection data from the previous study. This paper also looks into the correlation between those inspection results and the performance degradation data. The objective of this paper is twofold: (1) to present a statistical analysis result of degradation data for field exposed crystalline silicon modules installed on 2-axis trackers between 8 and 13 years. The analysis should provide reliability prediction for up to 30 years of field operation. (2) To investigate the correlation between performance degradation and inspection data. Inspections include visual observations, IR scanning, and electroluminescence imaging.