Leveraging Drones for PV Plant Inspections

Drones are reducing labor costs, maximizing performance and providing granular insights for PV systems. In addition to enabling the taking of aerial photos, they support aerial thermography, capturing PV system performance data with thermal infrared (IR) cameras.

Also known as an unmanned aerial vehicle, a drone is an aircraft without a human operator aboard. A drone in combination with a ground station, typically a smartphone or tablet and controller, comprises an unmanned aerial system. Drones can be either fixed-wing types, which resemble an airplane, or multicopter models, which have several propellers and can hover in place.

O&M providers, EPC firms and asset owners are increasingly adopting drone technology for its lower data acquisition costs and superior data collection and analysis flexibility compared to boots-on-the-ground inspections with handheld analysis tools. In the past 2 years, machine learning and artificial intelligence, improvements in drone hardware and a favorable regulatory environment have combined to push drones to the forefront of aerial thermography.

“This year, we are flying drones over most of our power plants under management,” says Angelo Purpura, director of operations at SOLV, a Swinerton company. “Asset owners are recognizing that drones can replace the majority of I-V curve tracing, which enables us to provide a faster, more detailed analysis and maximize output.” SOLV recently completed a survey of a utility-scale (200 MWdc plus) installation via drone in less than 6 hours, and the inspection team produced its detailed report in less than a week. Comparable assessment with I-V curve tracing would have required weeks to perform. SOLV’s aerial imaging approach resulted in a savings of approximately 50%.

Put Drones to Work for Your Business

Drones put the power of aerial thermal inspections in the hands of EPC firms, O&M technicians and regional drone service providers. They can minimize or eliminate the need for ground site inspections with handheld I-V curve tracers and other analytics tools, improving overall worker safety while lowering O&M cost. Some of the largest national insurance companies, such as State Farm and Travelers, also now use drones for rooftop inspections.

Drones offer some powerful features, such as tunable deliverables. For instance, an EPC firm may opt to obtain an extremely high-resolution dataset on areas of interest, such as a defective subarray for warranty prosecution, or a site-level overview. These tunable variables create flexibility in the type and means of data collection. The rapid growth of the commercial drone sector has fostered the creation of automated, industry-specific software with flexible outputs including paper reports and backend system integration. As a result, aerial inspections typically streamline reporting turnaround time, in some cases allowing preparation of comprehensive reports in a single day.

Aerial inspections complement on-site data collection systems and their cloud-based monitoring counterparts. Asset-monitoring solutions that utilize on-site hardware provide monitoring with a high temporal resolution (the precision of a measurement with respect to time) or constant measurement. These solutions also typically monitor energy and environmental data to optimize asset performance. Drones complement these systems with high spatial resolution that can localize issues to the cell level and also detect possible site-level issues such as vegetation growth or excessive soiling. Monitoring solutions can guide plant operators to determine when and where to send a drone within a PV system.

Keith Aubin, geographic information system manager at Enel Green Power North America, used drones to inspect over 70 MWdc of capacity across nine power plants in 2017. In 2018, he is working to spread this technology to Enel Green Power’s O&M teams around the world. “As we standardize our process for localizing string and module-level defects, we expect to save significantly on the labor cost to manually identify, log and correct issues.”

Drones make aerial thermography accessible for commercial and industrial (C&I) solar projects by improving site access to these installations. The fixed cost to deploy a manned aircraft can easily outweigh the benefits for C&I sites. A technician with a drone in his or her vehicle, in contrast, can quickly deploy it during a site visit, completing data capture in minutes. C&I sites tend to be located in more densely populated areas, making it easy to source qualified drone service providers.

Worker safety is another important consideration in favor of using drones to perform inspections. PV arrays in C&I installations are often located on facility rooftops or carports that expose workers to fall hazards. Technicians that perform system inspections on rooftops require special fall protection training and equipment.

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