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| Fig. 1: A 49.5 MW solar farm in Vietnam. (Source: Wikimedia Commons) |
Solar power is the third largest renewable energy source currently used in the United States. The abundance of raw solar energy available to the earth has led to large efforts in recent years to improve solar panel technology in order to make solar assets more efficient and cost effective. Aerial thermography is the latest technology for inspecting photovoltaic (PV) solar panels and is proving to be the superior means of optimizing solar assets at the commercial level. This report will explore the benefits offered by aerial thermography of PV systems over traditional inspection practices.
Traditional means of inspecting PV solar farms includes in-house technicians conducting field walks and I-V curve tracing. I-V curve tracing uses sensors on strings of PV modules to measure current and power as a function of voltage, comparing measurements to expected numbers in order to determine which strings are underperforming. [1,2] Field technicians, in addition to making repairs where needed, also inspect for visible wear and tear damage. For large farms, both of these practices have efficiency problems. I-V curve tracing is expensive and time consuming. Because of this, standard practice for larger farms (above 25 MW capacity) is to inspect only a small fraction of the total farm every year. This limitation means that a module could be underproducing for several years before any steps are taken to remediate it. Additionally, I-V curve tracing exposes technicians to high voltage DC components, meaning that technicians must be in full arc-flash equipment during testing and poses a safety hazard.
Aerial PV inspection involves using drones or manned aircraft to fly over the entire site and scan all modules using infrared (IR) cameras. Scans are stitched together to form a complete thermal map of the solar farm. Light spots in the map indicate where potential problems may lie. Problems with strings or individual modules can be spotted easily. Aerial inspections can be done in a matter of hours and require far less manpower to conduct. [3] Typical aerial inspection drones can cover up to 10 MW per hour, whereas manual inspections would be lucky to cover 1 MW in 10 hours of work. Fig. 1 depicts a 49.5 MW solar farm in vietnam. As one can see from the image, solar farms can cover vast areas of land, and inspecting them can be a painstakingly long process for field technicians. With aerial inspection, field technicians can be alerted where specific problems exist rather than having to manually inspect each and every module in the farm. IR cameras can even detect micro-damages in individual solar modules that are too miniscule for field technicians to uncover manually. Aerial thermography allows for entire solar farms to be inspected in a single day, rather than only a small fraction. Aside from convenience and speed of results, aerial inspection is also significantly cheaper than manual inspection. [4] Aerospec Technologies, a company that provides aerial inspection services, has estimated that their services save clients an average of $1,916 per MW per inspection. Clients with large solar farms can easily save hundreds of thousands of dollars annually using aerial inspection services. Clients can also expect a relatively low margin of error for estimations of power output loss, which typically fall between 0.5%-5%. Additionally, as inspections are done by drone or aircraft, the amount of time that field technicians are required to spend in hazardous environments is reduced down to only the amount of time spent actually making repairs.
Aerial thermography solar PV inspection is superior to traditional manual inspection and I-V curve tracing due to its increased efficiency, cost-effectiveness, and safety. Drones and aircraft can inspect solar farms at rates that are orders of magnitude faster than manual inspection. Time efficiency turns into reduced labor cost and reduced hazardous manhours. Aerial inspection allows maintenance of solar modules to be performed often and efficiently, saving solar PV farm owners money and time.
© Daniel McColl. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] P. Papageorgas et al., "A Low-Cost and Fast PV I-V Curve Tracer Based on an Open Source Platform with M2M Communication Capabilities for Preventive Monitoring." Energy Procedia 74, 423 (2015).
[2] F. Mallor, "A Method for Detecting Malfunctions in PV Solar Panels Based on Electricity Production Monitoring," Solar Energy 153, 51 (2017).
[3] P. B. Quater et al., "Light Unmanned Aerial Vehicles (UAVs) for Cooperative Inspection of PV Plants," IEEE J. Photovolt. 4, 1107 (2014).
[4] D. H. Lee and J. H. Park, "Developing Inspection Methodology of Solar Energy Plants by Thermal Infrared Sensor on Board Unmanned Aerial Vehicles," Energies 12, 2928 (2019).
