Manufacturers of thermal imaging cameras, e.g. FLIR, note that PV module thermography can be performed when the incident radiation on the surface of the Pv modules is at least 500 Watt/m2, and preferably above 700 Watt/m2.
Moreover, during thermography, the incident radiation must be measured with a pyranometer, in order to verify that it is within permissible levels.
Furthermore, in order to avoid incorrect measurements due to reflections from the sun and clouds, it is necessary that thermography be performed on the rear side of the PV modules.
Additionally, the PV modules must be disconnected so that no current passes through them in order for their heat to be the result of solar radiation only. Then, a load must be applied to each of them so that they can be visualised.
Finally, given that the viewing angle of the PV modules is also important, the experience of the thermal camera operator is essential in this type of inspection.

It can therefore be seen that thermography is a complex process, requiring strict conditions. Especially regarding installations of a few dozen, hundreds, or even thousands of PV modules, it is virtually impossible to fully meet these conditions so as to draw safe and documented conclusions about the condition of the PV modules.
At the same time, it should be understood that thermography can reveal PV module defects on the macro level, but microcracks are almost impossible to reveal, regardless of the resolution that a thermal camera may have. These microcracks, however, are the most important cause of reduced performance.