## 3 Results and Discussion
### Measurements
#### 3.2.4 Infrared Thermographic Analysis of Undamaged Modules  
After the initial analysis, the identification of potential reflections on the site, and taking into account the time needed to inspect one module on average 27 min, it became clear that only 50 % of the available modules can be inspected during the day under the same conditions. The following thermograms show the thermal patterns of the modules in the short-circuit state. To facilitate visual comparison, the temperature range of the pallet is set to a temperature value from 20 \({}^{\circ}\)C to 100 \({}^{\circ}\)C. Figure 20 shows the thermographic analysis of module number 2 (left) and number 3 (right). Figure 21 shows the thermographic analysis of the front side (up) and the backside (down) of module number 4. A hot spot was noticed on module number 4, which can lead to module degradation. The observed anomaly significantly exceeds the temperatures predicted by the standards. Based on previous findings, we decided to investigate the background of the module using a camera with a wider shooting angle FLIR E6 and determine the exact temperature values. The reflected radiation of the substrate was taken from the images recorded with E60 bx. Figure 19: Change in cell temperature of the first five rows of module. Figure 20: Thermographic analysis of module number 2 (left) and number 3 (right). The comparison of the sizes illustrated in the figures shows that the recording parameters were well chosen. The learned hot spot, with its temperature magnitude of 114 \({}^{\circ}\)C, can lead to the destruction of the module, so it was declared defective for further use. Figure 22 shows thermographic analyses of modules 5 and 6, while Figure 23 shows the thermographic analyses of modules 7 and 8. Figure 21: Thermographic analysis of the frontside (**up**) and backside (**down**) of module number 4. Figure 22: Thermographic analysis of module number 5 (**left**) and module number 6 (**right**). The analyzed modules showed different thermal patterns, resulting from the short-circuit current at different solar irradiance values. The recorded values corresponded to the information found in [18,20,29]. Table 12 shows the values of solar irradiance and contact measurement values of the module temperatures that preceded the thermographic test. A graphical representation of the solar irradiance over the thermographic measurements on the modules is provided in Figure 24.  
The graphical representation of solar irradiance over the thermographic measurements must be corrected in order to get precise data according to (1), using the data presented in Figure 25. The average wind speed for the studied location in September is 1.7 m/s, based on the Croatian Meteorological and Hydrological Service data. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Module** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** \\ \hline W/m\({}^{2}\) & 825 & 850 & 833 & 855 & 827 & 781 & 778 & 720 \\ T (\({}^{\circ}\)C) & 38.3 & 37.3 & 34.8 & 41.8 & 45.3 & 39.3 & 40.3 & 41.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Solar irradiance and module temperature at the time of the measurement. Figure 23: Thermographic analysis of module number 7 (**left**) and module number 8 (**right**). The minimum temperature of the module in the short-circuit state, given in Figure 26, shows a growth trend in the daily temperature for September. The increase in the value of module 4 is a result of heating caused by significant dissipation of the hot spot. If we exclude the extreme hotspots on module number 4 and module number 8, the data shown in Table 13 indicate that the difference between the observed maximum and minimum temperature values is 20.5 \({}^{\circ}\)C, which is an average increase of 45.16%. The maximum temperature values, averaging 65.8 \({}^{\circ}\)C, are not a problem for module components under continuous operation. A comparison with the data from the analysis of the new modules in Table 6 shows that the data in Table 13 have similar values.