## 3 Results and Discussion
### Pilot Project of Infrared Thermographic PV Analysis
performed using a VOLTCRAFT RS-350 with an uncertainty measurement of \(\pm\) 0.5 \({}^{\circ}\)C at 100 \({}^{\circ}\)C. The calibration results are shown in Figure 6.  
When analyzing two cameras, calibration data are necessary to reconcile the measurement results because the FLIR E60 bx camera shows an average temperature of 0.8 \({}^{\circ}\)C higher, while the FLIR E6 shows an average temperature of 2.9 \({}^{\circ}\)C higher. To prepare the measurement procedure, a pilot analysis of a small unused module with dimensions of 52 \(\times\) 32.5 cm, placed on supports intended for field use, was performed. Unfortunately, the nameplate, which should be present in accordance with the EN 50380: 2003 Datasheet and nameplate information for the PV modules (or UL 4730), was not attached to the module. Figure 7 shows a photograph of the pilot setup, taken at 720 nm. The expected values of the temperature difference, according to the literature [11], were in the range of 10 \({}^{\circ}\)C. Figure 8 shows the temperature distribution on the module, recorded by the FLIR E60 bx camera. Figure 5: FOV and IFOV of the available Flir E6 and Flir E60 bx cameras. Figure 6: Calibration results of the Flir E6 and Flir E60 bx cameras. Figure 7: Photograph of the pilot setup, taken at 720 nm. Figure 9 shows the thermal patterns of the bottom and top sides of the module, taken with a wide-angle camera, showing higher temperature values on the glass than a module shot with a narrow-angle camera at a higher distance. This analysis indicates that the influence of operator radiation during the thermographic analysis of the PV modules was not significant. A comparison of the thermograms of the modules recorded with the E6 and E60 bx cameras clearly indicates that the apparent temperature of the glass surface will vary significantly depending on the shooting angle, due to the environmental effects. Under real conditions expected in the field, it would not be possible to determine the exact share of reflected radiation that may occur at microlocations. This will be especially true for changes in the position of the sun, which heats the environment, and the elements of which become thermal emitters. The extent to which the camera position affects the reading of the temperature value is best illustrated in Table 3, which provides a comparison of the results of recording the apparent temperature of the glass surface and the substrate temperature using two cameras. Figure 8: Pilot module thermogram recorded by the FLIR E60 bx camera: bottom side (**left**), top side (**right**). Figure 9: Pilot module thermogram recorded with the FLIR E6 camera: bottom side (**left**), top side (**right**). and 160 \({}^{\circ}\)C are not adequate; high cure temperatures of up to 170 \({}^{\circ}\)C and/or long cure times can generate acetophenone, which causes yellowing in the EVA (Ethylene vinyl acetate). According to more recent literature [21], lamination takes place at 150 \({}^{\circ}\)C. According to [15], the operating temperature range to be expected in practice is between 30 \({}^{\circ}\)C and 80 \({}^{\circ}\)C. The reason for the analysis of potential temperature extremes is the fact that the power plant is no longer under normal operations, and testing is only possible with modules experiencing short circuit, i.e., at the highest possible current, which also leads to the highest thermal stress. Otherwise, under normal operations, the increase in temperature of the module parts can be expressed by a simplified expression that takes into account wind speed, irradiance, and ambient temperature [18], given as (1):  
\[T_{c}=T_{a}+\left(\frac{0.32}{8.91+2\cdot V_{f}}\right)\cdot G_{t}\quad\left(V_ {f}>0\right), \tag{1}\]  
where \(T_{a}\) is ambient temperature in K, \(T_{c}\) is cell/module operating temperature in K, \(G_{T}\) is solar irradiance in W/m\({}^{2}\), and \(V_{f}\) is wind speed, ranging between 1-15 m/s.