Automatic inspection of Photovoltaic systems with thermal imaging drones

Abstract

Due to its economic and environmental advantages, solar photovoltaic (PV) energy has attracted significant interest in recent decades. In addition, thanks to the enormous potential of solar energy, today, photovoltaic (PV) energy is one of the fastest-growing clean energy resources. Thereby, the number of grid-connected photovoltaic (PV) systems installations is constantly growing worldwide than ever before. Commonly, solar photovoltaic (PV) power plants are comprised of hundreds or thousands of solar PV modules, which represent the main component for PV power production. However, due to various types of stresses, PV modules might be subjected to different kinds of failures and defects over their lifetime. Thus, the out-put power of the PV power plant might be dramatically reduced. The most common types of PV modules failures are snail trails, cracked PV cells, delamination, bypass diode failure, hot spots, EVA degradation, short-circuited sub-string, etc. Therefore, regular inspection is essential to maintain the optimal efficiency and energy yield of the PV systems. Different techniques are used for the detection of PV modules defects and failures. The most known inspection techniques are I-V curve measurement, electroluminescence (EL) imaging, fluorescence imaging, and infrared thermography. The conventional manual inspection methods such as visual inspection and I-V curve measurement are time-consuming, inaccurate, and require significant human work. Furthermore, some of the inspection techniques are applicable only to identify specific PV module defects and are not helpful for other defects types. In recent years, the infrared thermography technique has become increasingly popular for inspection defects and failures of PV systems. This technique is fast, contactless, and cost-effective. In this technique, defective PV modules can be detected by infrared camera depending on the temperature deviations of the modules. In this respect, unmanned aerial vehicles (UAV) or drones equipped with thermal infrared imaging have become a powerful technique to detect and identify the precise location of detective cells and PV modules in PV systems. In addition, this technique can be carried out under real operating conditions of the PV system. Moreover, applying drone thermography technology for PV systems inspection saves time and reduces maintenance costs compared to the traditional inspection methods. The main goals of this thesis are to explore and evaluate the use of aerial thermography technology to detect possible PV modules failures and defects at Tampere University Solar PV Power Research Station. This thesis was carried out in cooperation with Cleaner Future Oy. DJI Mavic 2 Enterprise Dual was used in this investigation as an inspection tool. The drone has dual infrared thermal and visual cameras. The practical measurements were carried out on 12th and 13th of May 2021. The thermographic and visual images of PV modules are captured during the measurements and subsequently extracted from DJI remote controller for further analysis. In this investigation, the achieved results showed that several defects and failures were detected by thermal drone camera, such as hot spots, EVA discoloration, and ac-cumulation of soiling. Finally, the study results have proven that the DJI Mavic 2 Enterprise Dual with its thermal and visual cameras was helpful and reliable to identify possible failures of PV modules at Tampere University Solar PV research power station.