Criticalities of the Outdoor Infrared Inspection of Photovoltaic Modules by Means of Drones

Photovoltaic plants are helping to reduce CO2 emissions, but the energy performance of photovoltaic systems must remain high throughout their operational life. Supervision and monitoring are mandatory for large photovoltaic plants because failures can cause high power losses due to the large number of photovoltaic modules. Infrared analysis is effective and reliable in detecting anomalies or failures in photovoltaic modules, but it is time-consuming and expensive when the infrared inspection of large photovoltaic plants is manual. Nowadays, the diffusion of unmanned aerial vehicles equipped with infrared cameras can support the fast supervision of photovoltaic plants. Nevertheless, the use of drones is regulated by international and national rules; consequently, it is not always possible to use a drone, or its utilization is limited based on geographic areas and/or authorizations. Moreover, infrared analysis requires additional requirements when done by drone, because the mutual position between the photovoltaic modules and the infrared camera affects the goodness of the infrared acquisition. This article discusses these critical issues, directs the reader to official, national, and geographic maps for drones, and suggests technical solutions for some specific issues not considered in the technical specification for the outdoor infrared thermography of photovoltaic modules. In particular, the paper proposes a systematic procedure for the legal and effective infrared inspection of photovoltaic modules by means of a drone and proposes improvements for some issues not discussed in the international rules: the correction of infrared images with respect to the view angle, the impact of a mid-wave and long-wave infrared sensor on the acquired image, and the impact of air transmittance.