As the world races to meet ambitious decarbonization targets, clean energy projects are breaking ground and coming online at a rapid pace. Designing, permitting and building projects is just the beginning for solar PV asset owners. Inspecting and maintaining solar systems are critical and ongoing efforts required so they continue to perform at their best, while also ensuring longevity, safety and ROI. Here are some common issues for technicians to look out for and the tools to use to detect underperformance.
Begin with a visual inspection
Conducting a thorough visual review of the PV system is foundational to each inspection. Through this initial step, you’re able to quickly identify areas of the system that require immediate attention, especially for matters that affect system safety. For example, indicators of dangerous arc faults can be flagged by looking for worn or loose connections, corrosion or gaps in insulation. This initial scan can also identify system components that would benefit from further investigation utilizing the appropriate tools.
Assess the electrical integrity to repair inefficient and damaged system components
Solar contractors will encounter many unforeseen system faults throughout the lifetime of a high-performing solar installation. These scenarios require a versatile toolkit, including digital multimeters, clamp meters, insulation resistance testers and irradiance meters. These tools can test components across the system to fully analyze performance and pinpoint problems, such as testing inverter efficiency, AC/DC voltage and current levels and fuse continuity.
A common issue that can be difficult to diagnose is ground faults, as they can have a variety of causes, including damaged conductor insulation, improper installation, pinched wires and water damage. Insulation resistance monitoring and residual current detectors (RCDs) can be used to detect DC ground faults and help prevent subsequent arc faults, which can lead to energized metal components and increased fire risk. It’s recommended to perform frequent grounding tests using insulation resistance monitors, or by placing RCDs on array conductors to measure for abnormal currents.
Identify temperature abnormalities to diagnose system faults
The origin of many PV system faults can also be diagnosed by capturing thermal images of critical PV system components. Thermal imaging cameras are indispensable for setting temperature benchmarks across the worksite, enabling the contractor to identify temperature anomalies that arise during maintenance procedures.
A higher-than-usual temperature reading in the internal system may indicate that the component is suffering from inefficient wiring or compromised transmission connectivity, indicative of high-resistance connections. Addressing high-temperature readings should be a priority in order to prevent the risk of fire and additional damage to other system components. High temperatures can also indicate an underperforming PV module or string. Alternatively, areas that present a lower temperature reading compared to the baseline may indicate a broken connection or blown fuse.
Address difficult-to-identify internal solar module defects
Solar contractors can use current-voltage (I-V) curve tracers to illuminate system faults, acting as an efficient alternative to the combined use of a digital multimeter, clamp meter and irradiance meter. I-V curve testing measures points between open circuit voltage and short circuit current, displaying a visual curve representing the PV power output. The displayed I-V curve helps contractors identify problems relating to bypass diodes, reduced current or voltage, series resistance and low shunt resistance.
I-V curve testing also helps to assess the financial benefit of certain procedures. For example, many PV systems in dry, dusty areas are faced with the issue of soiling loss, where dust and grime on panels reduce the ability of sunlight to effectively be converted to energy. I-V curve testing can quantify this loss by comparing the measurements of a string of dirty modules against an expected baseline. The selected array of dirty PV modules is tested, then washed and re-tested to compare the results from the initial test. The results from each test can be used to measure the impact of soiling and assess if array cleaning is worthwhile.
Inspection and maintenance can be tedious and require the use of various specialized tools to adapt to unpredictable situations. Investing in multifunction tools and testers with integrated reporting software can lighten a technician’s toolbelt and backpack. High-quality tools help contractors quickly diagnose and resolve system performance issues, reducing the time spent at each site and avoiding costly repairs. The best tools will not only be accurate, but also safe, durable and easy to use.
Rick Hart says
Interesting – however in systems with String inverters – overall output monitoring does not provide data on the individual modules. However systems with Enphase Micro-Inverters and the individual monitoring of these modules – gives a history of the actual modules performance. You can review the modules installed and see differences in the panel performance and see trends of panel performance issues. One one project with the Dallas VA – the Sanyo Panels failed and Panasonic assumed the warrantee issues – yet the response from Panasonic required proof of panel degrading – which the NREL had written papers on these panels and issues. If the system would have been Enphase and had the individual monitoring (Enlighten) then the panel issue(s) and warrantee would have been easy to show. Some of these tools were used by Panasonic when visiting the site – but the greatest tool for performance that I have used is the individual monitoring. This truly shows a pattern that can be discussed and shown to a panel manufacturer for warrantee / panel performance issues. The Dallas VA ended up eating 1700 panels that degraded and with no resolution on the warrantee.