An investigation into hot‐spots in two large grid‐connected PV plants

Abstract

This paper details an investigation into the appearance of hot-spots in two large grid-connected photovoltaics (PV) plants, which were detected after the visual inspection of trackers whose energy output was decreasing at anomalous rate. Detected hot-spots appeared not only in the solar cells but also in resistive solder bonds (RSB) between cells and contact ribbons. Both types cause similar irreversible damage to the PV modules, but the latter are the main responsible for the detected decrease in energy output, which was confirmed in an experimental testing campaign. The results of this investigation, for example, how hot-spots were detected or their impact on the output power of PV modules, may be of interest for the routine maintenance of large grid-connected PV plants.

Observed degradation in photovoltaic plants affected by hot‐spots

“…This concentration of the current in small areas is responsible for the temperature increase in these areas and is therefore the cause of the hot‐spots observed. This cause is different from the one found in other plants also experiencing soldering problems .…”

“…This concentration of the current in small areas is responsible for the temperature increase in these areas and is therefore the cause of the hot-spots observed. This cause is different from the one found in other plants also experiencing soldering problems [6]. Weak solder joints were observed not only on cells affected by localized heating phenomena but also on cells that were apparently sound and even on cells of modules that had never been exposed to solar radiation.…”

Tracking and back‐tracking

“…That helps us to understand why it is not implemented in today's commercial vertical axis trackers. However, it must be noted that shade is prone to inducing hot-spots, which can even result in PV module destruction after a certain operating time [12] and that back-tracking fully avoids shade. Hence, even irrespective of the energy balance, we think back-tracking can still be attractive in practise.…”

Reliability of a 13 000‐SHS photovoltaic rural electrification programme

“…This battery failure is known in reliability engineering as a secondary failure, as it is caused by the failure of another in the solar cells, and even in the interconnections between cells (bus), as a result of defects in the manufacturing process, which can be detected by infrared thermographic cameras. The affected cell becomes reverse biassed and dissipates power in the form of heat [13,14], and can destroy the PV module.…”