When it comes to solar O&M, site inspection is a key component. Whether through ground- or roof-level inspections or aerial assistance, understanding how a system is performing ensures a successful lifespan. Although inspection services by drones are on the rise, manned aircrafts are also excellent at providing precise information on a solar system’s performance.
Solar Power World talked to Heliolytics, a Canadian aerial inspection team specifically catered to the solar industry, about its services and how precisely its aircraft-mounted sensors can pinpoint system problem areas. Besides boosting performance, consistent aerial site inspections can also help with insurance claims in cases of extreme weather damage (like hurricane, tornado and flood events we described here). Heliolytics CEO Rob Andrews answered our questions.
SPW: What services does Heliolytics offer?
Andrews: Heliolytics provides aerial inspections and system performance analytics for solar PV systems. We have developed an aircraft-mounted sensor package and integrated artificial intelligence (AI) analytics package for the inspection of PV projects of all sizes. We have inspected over 6 GW of projects globally.
We use a manned fixed-wing aircraft to collect infrared (IR) and visible imagery of a site, then apply our analysis package to locate and classify every string- and module-level defect on a site that shows a thermal signature, indicating a reduction in energy production. We provide a digital “as-built” map of the site with all the fault locations and classifications, so clients and their technicians can easily identify what the issues are on the site and where to find them when they go to remediate the site.
SPW: What type of solar customer most benefits from your services?
Andrews: We work globally with customers on their distributed portfolios with sites ranging in size from 10 kW to over 700 MW. Our typical customers include system owners, O&M providers, EPC contractors, insurance providers and independent engineers. Our tools are aircraft-mounted, so we are able to service large portfolios of distributed rooftops as well as some of the largest ground-mount sites in the world.
SPW: How does Heliolytics’ method of inspection differ from others?
Andrews: Our manned aircraft-mounted camera system and integrated AI analytics package is specifically designed for the inspection of PV arrays. We have built, from the ground up, a system specifically tuned to the needs of the PV community.
This translates to differences in the capture, classification and delivery of the data we collect. Our aircraft-based platform allows us to provide higher resolution visible and infrared imagery at a faster integration time and higher thermal sensitivity than drone imaging equipment. This allows us to detect much subtler defects, including individual cells and junction box heating. Because of our high speed of acquisition, we can collect data quickly—up to 30 minutes per 50 MW—which allows us to capture a clear thermal snapshot of a site that would normally take days or weeks to inspect.
On the processing side, because we have consistency in our dataset, we have developed new AI-based software specifically designed for the analysis of PV systems, and this provides consistency in detection across large portfolios. We have also leveraged this to provide digital delivery options, which allow the data collected from aerial inspections to be integrated directly into existing customer workflows.
SPW: Why is aerial inspection important on solar arrays?
Andrews: Aerial inspections can uniquely provide 100% visibility into DC system capacity, allowing faster and consistent remediation of string and other DC capacity losses. In one test, we compared our aerial inspection to ground-based string testing and saw that ground testing found only 20% of what we found from the air. The detection of these faults, which would not be found by traditional O&M procedures, provide a payback on services through improved site energy generation in addition to reduced labor costs.
After the scan, these inspections allow for remediation optimization, where a client can quickly asses where remediation is most critical and optimize repair schedules. Technicians can spend their time on site fixing problems rather than searching for them, and they’ll know exactly what type of faults they are dealing with prior to stepping on site.
SPW: How often would you suggest getting aerial inspections?
Andrews: We usually recommend annual site scans to our clients. Annual site scans provide a big-picture understanding of how sites are performing and/or degrading over time. They also help our clients identify performance issues in particular parts of their systems, such as a specific module type that is prone to certain faults on their site, or the occurrence of distributed string faults on the site.
The most effective use of aerial inspections is coupled with advanced data analysis, where aerial data can provide the annual periodic true-up to data analytics, and the optimized performance models can be used throughout the year to better identify DC health issues between scans. It is important to note, however, that due to uncertainties in data collection, data analytics alone cannot identify all the defects identified by aerial inspection, and both provide a good complement to each other.
SPW: What are the most common faults or failures you’ve found? Do you suggest remedies?
Andrews: Aerial inspection can identify any defect which is causing a significant difference in performance between a module and its neighbors. Examples include major anomalies like string, combiner and module outages to more subtle defects like individual hot-spots, PID, module mismatch and MPPT errors. In addition, our visible imagery is critical for the detection of module breakage, dirt and fouling of modules, racking shifts and other visible anomalies.
Based on our data collected from over 6 GW of site inspections, we find that a given site has an energy weighted average DC loss of approximately 1.2%, and median weighted average DC loss of approximately 0.4%. This represents the level of loss which is being missed by current O&M practices and provides an opportunity for site optimization and energy improvement.
By energy impact, the most common fault we find are distributed string outages, which generally have too small of an energy impact to be detected by data analytics alone. The most common failure mode we find are sub-module failures which represent one-third of a crystalline module being deactivated, generally due to soldering issues or junction box damage.
Remediation recommendations depend on the level of energy impact associated with a particular fault, along with their distribution in a site. It is important to flag situations where groupings of failures may represent a serial module defect in a system.
SPW: How can aerial inspections help in extreme weather events?
Andrews: Annual aerial IR scans provide regular site assessment and benchmarking for solar PV sites, which can expedite the process of insurance claims when sites are damaged due to severe storms and other weather events. If we have performed consistent, annual scans for a client, we are able to assist them if one of their sites is affected by a damaging weather event. We create a differential report for this site, where we identify all the pre-existing defects on a site from our most recent aerial inspection before the weather event and what new/different defects have appeared on the site after the weather event from a post-event aerial inspection. This provides a clear picture of the site damage caused by the specific event for the client, including what damage can be claimed through insurance and what issues needs to be remediated on site by the client.