As the cost of solar electricity has fallen, the number of grid-connected solar PV systems has grown into the millions and utility and energy companies are building solar power stations with hundreds of megawatts (MW). Solar PV is rapidly becoming an inexpensive, low-carbon technology to harness renewable energy from the sun. The current largest PV power station in the world is the 850 MW Longyangxia Dam Solar Park, in Qinghai, China. In the U.S., California boasts four of the world’s largest plants.
Solar plants inspections are vital to ensuring the solar cells are performing properly, minimizing potential power loss; they are also legally required to maintain certification. By law, solar plants need to be scanned with an infrared camera annually. Drones can provide a comprehensive look by providing accurate imagery of a plant in significantly less time, and with greater accuracy, than it might take for a handheld inspection. Drones are bringing airborne analytics to utility-scale solar operations like PV equipment inspections, resulting in strong time and cost savings. Further, drones and the sophisticated software that powers them are transforming operations and management practices for commercial solar companies.
Options for Plant Inspections
Before drones, there were two choices for inspecting strings, PV panels, and other equipment. PV technicians could conduct inspections on truck rolls and on foot with a handheld thermal camera, inspecting thousands of acres and tens of thousands of panels in large solar farms, a project that can take weeks and often results in flawed data. Inspections have been typically a reactive task, focused on pinpointing problems versus preventive maintenance to reduce equipment downtime. The other choice has been to conduct inspections with manned aircraft mounted with sensors, which can be faster but more expensive, at about $1,000 to $2,000 an hour.
Solar Farm Efficiencies from UAS
Unmanned aerial system (UAS) puts new and emerging data collection, analysis, change detection, and artificial intelligence applications within reach for solar operations managers. Drone capabilities—remote sensing with LiDAR and infrared (IR) technology, high-resolution photography including UV and other spectral, HD video—have potential to keep plants running at peak capacity at more manageable cost.
For example, a pilot can fly a drone equipped with IR sensors over the facility to quickly detect hot spots on PV panels, indicating subpar performance. A unmanned aerial vehicle (UAV) mounted with a high-definition camera allows plant operators to see, capture and log detailed videos and still images of assets that need maintenance, catching them before something goes wrong. This means servicing issues are proactively identified, problem units are brought back to full capacity faster, and plant reliability and output both benefit.
Software can also automatically tag and record GPS locations, temperatures, and other metadata, so plant operators have a searchable map with photos as part of the record for each inspected asset. Plus, the flight planning aspects of a drone inspection, including Federal Aviation Administration approval to fly in busy airspace, is now automated, shaving permission time from months to literally seconds.
Here are some of the ways drones aid in thorough, cost-effective solar utility inspections:
- Finding malfunctioning units in an array.
- Performing preventive maintenance. Panels, mounting systems, wiring, monitoring equipment, and other plant components can be visually imaged for dust and dirt, snail trails, leaves, corrosion, defects, cracks, and water or insect intrusion.
- Monitoring vegetation to keep foliage from casting shade on strings.
- Detecting equipment that may be in danger of overheating (combiner and junction boxes, inverters).
- Assessing damage following wind, seismic, flood, fire, or electrical storm events.
- Inspecting transmission lines.
- Monitoring fencing for security purposes.
When It Does and Doesn’t Pencil Out
Piloted helicopters and planes may still make sense for inspecting facilities of more than 25 MW or covering more than 5,000 acres, since they can carry larger sensor packages that offer economies of scale. For areas where aircraft aren’t readily available for hire, drones can be cost-competitive due to the flight hours necessary to just get to the site. And UAS is proving superior to manned aircraft for site assessments. SunPower, a leading global solar power innovator based in the Silicon Valley, uses drones to survey prospect plant sites, which enables quicker and easier access to remote sites than manual survey methods and allows for faster evaluation of multiple potential sites.
Drones & Commercial Solar: A Power Couple
UAS is bringing powerful airborne analytics to utility-scale solar operations that are translating into very attractive time and cost savings. With the global capacity of utility-scale solar PV expected to be eight times the 2014 level by 2040, drone technology and solar are well positioned for a growing, productive partnership.
Cost Comparison: Ground Crews vs. Drones vs. Manned Aircraft for Commercial Solar Siting & Inspections
*A 2015 EPRI study, done before drones were being widely used for solar farm O&M, estimated a cost of $10 to $25/ kW-yr. for inspections and other standard preventative maintenance activities that would typically be performed at most utility-scale sites (e.g., visual/structural system inspection, wires and combiner box inspection, infrared thermography scanning, IV curve tracing, and inverter maintenance).