Solar companies involved in the design, build, management, and/or maintenance of PV systems are increasingly moving to UAS (drones) to replace field work that take large amounts of time and money. Field walks, IV curve tests, voltage checks, and handheld thermal scans of modules are just a few examples of tasks being replaced with drones by O&M teams around the world. Drones set up with both thermal (IR) and high-resolution (RGB) imaging cameras allow for common mislabeled anomalies (ie. soiling) to be properly identified and not mistaken for module hot spots.
Before we get started, it’s important to make sure you’re familiar with the general workings of PV systems. This is a must when it comes to inspecting solar sites effectively with a drone. Here’s a quick breakdown:
Solar sites → A solar site can have hundreds of rows→ Single or multiple strings are within a row→ Strings are made up of modules→ Modules are made up of several photovoltaic cells (Polycrystalline, amorphous, TPV, multi-junction)
1. Combiner off-nominal (warm) or offline
Site level issues such as off-nominal or offline combiners pose a serious threat to the efficiency of a PV system. An anomaly of this scale requires immediate maintenance and is always considered an issue of the highest priority. Combiner anomalies are often mistaken for string level issues. However, their identifying quality is when entire rows clustered together present as warm abnormal geometry in your thermal imagery. To determine it is a combiner issue always reference the as-built. Below is an example of a off-nominal or offline combiner.
2. Inverter off-nominal (warm) or offline
Inverter anomalies are also a high priority issue that can drastically affect the power production of a solar site. Similar to combiner level issues, inverters present themselves in thermal imagery as multiple rows in a unique geometry that appear warm or offline. Always reference the as-built drawing and site wiring to confirm that it is an inverter issue. Examples of inverter anomalies include:
3. Discrepancies from as-built – missing modules, incorrect build
Another common anomaly often identified with a drone inspection is discrepancy from the as-built documents, shown through missing modules, or incorrect builds. These differences are often missed from ground level, but easy to identify within an aerial inspection dataset. Before you perform your PV system inspection make sure you have documents such as site information, layout, and as-built diagrams for reference. When entire modules/parts of PV strings are missing, overall DC power production is dramatically affected.
4. Weather damage – hail damage, flooding, windstorm, tornado
With little to no protection PV systems are regularly exposed to the elements and extreme weather conditions. Tornadoes, lightning, high-speed winds, hail, and flooding can all cause tremendous damage to solar sites. Large hail can cause cause shattering, while strong winds can uproot and displace modules from their original position. Although it may not be easily identifiable with system monitoring, weather damage can greatly impact PV health/performance and requires immediate attention.
5. Delamination and Other Types of Potential Module Anomalies
Delamination and other suspected module defects are commonly found on both new and old sites. Delamination and other module defects can be spotted in either thermal (radiometric) or RGB imagery, depending on the anomaly, and can appear in several forms. They most commonly look similar to:
Are you interested in learning more about UAS, drone inspections of solar assets, and having your data converted into PV analytics and system reports? If so, please contact us here and our team will be in touch.