Thermal Infrared and Visual Inspection of Photovoltaic Installations by UAV Photogrammetry—Application Case: Morocco

A case study building visible and thermal orthomosaics of PV modules with a small drone and photogrammetry, to find soiling, cell cracks and hot spots. On small installations in Morocco, imagery at about 1 mm and 2 mm ground sampling distance showed cracks clearly at 1 mm but less so at 2 mm. The onboard 80x60 px thermal camera was too coarse for most datasets, while data from a 5,012-module Swiss plant yielded hot spots that matched the operator's report.

Key findings

• Cracks on four cells clearly visible at about 1 mm GSD, harder at about 2 mm
• Processing time cut by up to 86% by reducing overlap and changing parameters
• Onboard thermal sensor (80x60 px, 0.1 C sensitivity) too coarse for most datasets; thermal orthomosaic GSD 13.4 cm
• Swiss 5,012-module plant: hot spots extracted that matched the operator's report

Limitations

• Very small Moroccan test installations (about 39 modules)
• Manual thermal calibration; camera model lacked lens distortion values
• Inconsistent count of installations between sections
• Atmospheric effects and authorisation costs noted