Hotspots in cells
Cracks, defects or partial shading make single cells run hot.
Thermal inspection
Solar plant drone inspection with thermal cameras.
By the NVX engineering team, New Delhi · 3 November 2026 · 6 min read
A thermal drone finds solar plant faults by their heat: a cracked cell, a failed bypass diode or a disconnected string runs at a different temperature from healthy modules. Flying a plant is far faster than checking modules one by one on foot, and the result is a map of every anomaly for the maintenance team. Here is what it finds, the conditions it needs and what a useful report looks like.
What a thermal inspection finds
Typical anomalies seen from the air.
Bypass diode faults
Show as one sub-string (often a third of a module) warmer than the rest.
String or module outages
A whole string or module that is not producing appears uniformly warmer.
Soiling and shading
Dirt, bird droppings and vegetation show as patterns that change after cleaning.
Connection and junction-box problems
Local heating at connectors and boxes.
Conditions for a valid thermal survey
Thermal results depend on the plant working hard. The international guideline for aerial thermography of PV plants, IEC TS 62446-3, calls for strong, steady sunlight (an irradiance of at least 600 W/m² on the modules) and stable conditions. In practice that means a clear day around the middle of the day, low wind and dry modules. Readings taken in cloud or right after cleaning can hide faults.
How the inspection is flown
A typical workflow.
Plan
Flight lines over the module rows at a height that gives enough thermal pixels per cell to see a single hotspot.
Capture
Radiometric thermal images (each pixel holds a temperature) plus visible images of the same areas.
Locate
Each anomaly is positioned on a map or site layout with row and module references.
Classify
Anomalies are grouped by type and severity so the maintenance team can prioritise.
What a good report contains
A list of anomalies with location, type, temperature difference and a thermal plus visible image for each; a plant map showing where they are; and a summary by block and severity. Ask for the raw radiometric images too, so the next inspection can be compared like for like.
FAQ
Solar Drone Inspection: common questions
Can a drone inspect a solar plant at night?
No. Solar thermal inspection needs strong sunlight so the modules are producing power; most faults only show when current flows.
What camera is needed for solar inspection?
A radiometric thermal camera, where each pixel stores a temperature, plus a visible camera to check soiling and physical damage.
How often should a solar plant be inspected?
Many owners inspect at commissioning, before warranty expiry and at least once a year, plus after storms or a drop in performance.
Is a drone inspection better than an I-V curve test?
They answer different questions. A drone finds where the faults are across the whole plant quickly; electrical tests then confirm and quantify specific strings.
Do I need permission to fly over a solar plant?
Drones fly under India's Drone Rules 2021. Check the airspace zone on DigitalSky; plants near airports or defence areas may need approval.
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