Abstract
The continuous increase of installed photovoltaic (PV) capacity, connected to the ongoing establishment of new PV plants, has led to increased scientific interest of making maintenance more efficient and reliable. An important role plays the inspection of PV modules as the core of PV systems. This work provides an economic cost-benefit analysis of different inspection techniques and their applicability in different climate zones. The focus lays on the most widely applied inspection infrared thermography (IRT) in comparison to the luminescence techniques electroluminescence (EL) and daylight photoluminescence (DPL). The luminescence techniques provide a more in-depth analysis of PV modules health status but are more difficult to conduct than IRT. The cost to conduct each of these methods is evaluated with a technical approach combining mandatory cost parameters and equipment-related thresholds limiting the imaging speeds. The initial analysis focusses on available time to conduct the different inspection techniques based on environmental parameter necessary for (such as sufficient irradiance) or preventing inspection (such as high wind speeds during aerial inspection). The analysis is done for different climate zones following the Köppen-Geiger Photovoltaic-Climate (KGPV) classification [1], and includes a sensitivity analysis. All parameters influencing the costs of performing an inspection (hardware, personnel, software, computing power, appliances) are identified and brought to inspection costs given in €/MWp. The main impact factor is the personnel costs, which are directly dependent on the imaging speed (MWp/h). To give precise values for inspection costs and allow for simple updates, all parameters influencing the imaging speed are evaluated and brought into an equation. This includes hardware related specifications like camera resolution, flight height and speed, structure of PV plant, as well as regulatory issues to ensure reasonable results, like ground sampling distance (GSD) or inspection type. This calculation will be published as a tool, which allows to alter all parameters, of the acquisition system as well as of the PV plant layout, to calculate the inspection costs of individual cases. As imaging speed is an important parameter, the current best practices (taken from literature and interviews with aerial service providers) are compared with future developments, which show the most significant changes in imaging speed, such as high-resolution InGaAs cameras, EL- and DPL-ready inverters. But also, the movement towards autonomous inspection is included: moving from piloted aircraft to autonomous drones or ground-based in-field robotic. Even though ground-based robots have a much slower inspection speed, once the personnel costs are taken out of the equation, they can become a profitable alternative. The comparison study is performed for three example PV plant layouts, comparing the different approaches and including all cost factors identified before. Finally, the benefit of conducting the individual inspection techniques is shown by analyzing the identifiable defects and their impact on performance and safety. Also factors which are not directly measurable are included, like preventive maintenance or knowledge for PV module re-use scenarios. Even though the costs for IRT are outperforming the ones for luminescence techniques now, preliminary results suggest that break-even will be reached soon, just by implementing recent developments into the common practice. A detailed analysis will be given in the final work.