IR Thermography

Key Takeaways

• IR thermography = thermal imaging of operating PV systems.
• Detects hot spots, connector failures, diode burnout.
• Drone-based for utility-scale; handheld for residential.
• Quarterly inspection typical for large plants.
• Complements EL imaging at commissioning.

What Shows Up in a Thermal Scan

A thermal camera doesn’t measure defects directly — it measures surface temperature, and reads a defect wherever something is dissipating power as heat instead of converting it. That makes IR thermography useful across several different failure modes at once. A hot spot from a shaded or cracked cell shows up as a localized bright patch on a single cell or cell group. A failed or shorted bypass diode runs warmer than a healthy one during bypass diode activation, since a diode that isn’t conducting properly forces the shaded segment to keep dissipating current it should be routing around. On the electrical side, a loose or corroded MC4 connector shows up as a hot point at the connection itself rather than across the module, because resistance is concentrated at that single joint.

Handheld vs. Drone-Based Scans

Which platform makes sense depends mostly on plant size. Handheld thermal cameras are common on residential and small commercial rooftops, where a technician can walk the array during a service visit and check anomalies against the layout by eye. Utility-scale plants use drone-mounted thermal cameras instead, flying a fixed altitude — typically in the 30–50 m range — to cover several megawatts of array area in a single day, well beyond what a ground-based inspection could manage in the same time. The tradeoff is resolution versus coverage: handheld scans catch finer detail on individual modules, while drone sweeps are built to flag which sections of a large plant need closer, module-level follow-up.

Related Reading

IR thermography findings are one of the ways a plant’s actual field performance gets reconciled against what was modeled at the design stage — if a string is underperforming the yield a study projected, a thermal sweep is often the first diagnostic step before a deeper root-cause investigation, a process covered in more depth in our piece on P50, P90, and P99 solar yield reports. Many of the hot spots a thermal scan turns up also trace back to shading that wasn’t fully accounted for at the layout stage, which is why getting the shading model right up front — using the tools discussed in our review of solar shading analysis software — reduces how much a plant depends on catching these issues after the fact. For a defect-detection method that works the opposite way, applying current to a de-energized module in the dark rather than imaging a live array in daylight, see EL imaging, which is typically used earlier in a module’s life at manufacturing and commissioning.