Solar PV thermal anomalies, from signature to fix
Every fault class our analysis can flag on an aerial thermal inspection — the same taxonomy that appears in your report. For each anomaly: what it looks like in a thermal frame, the typical temperature differential, what causes it, what it costs you, and what to do about it.
Guides
IEC TS 62446-3 thermal inspections, explained
What IEC TS 62446-3 covers for aerial thermography of PV plants: abnormality classes as typically interpreted in industry, the ≥600 W/m² irradiance requirement, capture conditions, and what a compliant report includes.
Read the guideDrone thermal inspection guide for solar PV
How to fly a solar thermal inspection that produces trustworthy findings: irradiance, nadir angle, sun glint, focus, thermal contrast and file handling — mapped to the capture-quality checks our analysis runs on every frame.
Read the guideWhat a solar thermal inspection costs
How solar PV thermal inspection pricing works — per-MW rates, minimum charges, what drives industry quotes up or down, and how to estimate your site's inspection cost instantly.
Read the guideAnomaly reference — 17 fault classes
Ordered as they appear in an inspection report, most severe first. Severity shown is the static per-type grade; a measured ΔT on your site can raise it.
String offline (open circuit)
An entire string of modules is electrically disconnected and producing nothing. It is usually the single largest energy loss visible on a thermal inspection.
Module offline (open circuit)
A single module is not exporting power while the rest of its string keeps operating. The whole panel runs warm because its bypass diodes carry the string current around it.
Missing module
A module is physically absent from the racking. The gap is obvious in imagery, and the electrical consequences depend on how the remaining string was left.
Multi hotspot
Several distinct hotspots on a single module. Multiple simultaneous hot cells usually mean widespread cell damage rather than a one-off local defect.
Hotspot
A localised area of one cell running significantly hotter than its neighbours — the classic PV thermal fault, and a defect that degrades the module further the longer it runs hot.
Heated junction box
The module's junction box is running abnormally hot — a high-resistance connection or failing diode dissipating real power in a small plastic enclosure. This is one of the few PV thermal findings with a direct fire-risk pathway.
Combiner box anomaly
Abnormal heating in or around a DC combiner box — typically a high-resistance termination or a failing protection device carrying the combined current of many strings. Treated as a safety-critical finding.
PID (potential induced degradation)
Potential induced degradation — leakage current driven by high system voltage degrades cells, showing up as a patchwork of warm cells that is worst near one end of each string. It is progressive and, caught early, partly reversible.
Double bypassed (2 substrings)
Two of the module's three substrings are being carried by their bypass diodes, so two-thirds of the module is out of production. Persistent double bypassing usually means hardware failure rather than shading.
Broken glass
The module's front glass is shattered or cracked. The module may still produce, but moisture ingress degrades it quickly and the electrical insulation can no longer be trusted.
Suspected PID
A thermal pattern consistent with early potential induced degradation, but not yet definitive. Flagged separately so it can be verified before committing to PID mitigation.
Single bypassed (1 substring)
One of the module's three substrings is being carried by its bypass diode, taking roughly a third of the module out of production. The key question is whether the cause is external (shading, soiling) or internal (cells, diode).
Bypass diode anomaly
A bypass diode behaving abnormally — shorted, leaking or overheating — rather than cleanly switching a shaded substring. Failed diodes cost energy and remove the module's hotspot protection.
Cracked cell
A cell with visible thermal evidence of cracking — current crowding through the intact portion of a fractured cell. Small today, but cracks propagate with thermal cycling.
Vegetation / shading
Shadows from vegetation or structures falling across modules. An operational finding rather than a module fault — but persistent shading costs real energy and can create genuine cell damage over time.
Soiling
Dirt on the glass — dust films, bird droppings, ash or lichen. Mostly an energy-yield issue, but hard localised soiling behaves like shading and can drive real cell heating.
Miscellaneous anomaly
A genuine thermal irregularity that does not match any canonical fault pattern. Flagged for field verification rather than forced into the wrong category.
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