The client manages a 4 MWp ground-mount solar farm in the East Midlands, built in 2011 with 16,794 modules on a single south-facing plane. Drone Media Imaging has inspected the site in previous years, but each visit is treated as a new and isolated solar farm thermographic inspection, so the result stands on its own evidence rather than leaning on an earlier report. The array is divided into seven reporting zones, matched to the installer’s original layout so that findings can be handed straight to the people who will act on them.

Fifteen years is the point at which an array’s condition starts to tell its own story. Cell defects that were minor at installation can grow, solder bonds fatigue, and connections in the field can open without anyone noticing at the inverter. The owner commissioned a detailed thermal inspection to understand where the risk sits now, which findings are about safety, which are about lost output, and which simply need watching.

Thermography works because a photovoltaic module that is not converting light into current turns that energy into heat. Under strong, steady sunlight a healthy module sits at a predictable temperature, so a cell, a sub-string or a whole run of modules that departs from it shows up clearly to a radiometric camera. The skill lies in reading that pattern correctly: telling a cell defect from a bypass diode conducting, a reflection from a real anomaly, and an open-circuit string from a module that is simply shaded. Drone Media Imaging, a trading name of VisualChaos Studios Ltd, provides that analysis to the IEC 62446-3:2017 standard.

The survey was flown on a September morning in two flights of about thirty minutes each, under a near-clear sky. Plane-of-array irradiance was 721 W/m² at the start of the first flight and 850 W/m² at the start of the second, rising to 881 W/m² by its end, all comfortably above the 600 W/m² minimum IEC 62446-3:2017 requires for a detailed inspection. Air temperature sat between 16 and 18 °C with light south-westerly wind, and the array was generating under load throughout. Each flight’s conditions were applied to the zones it covered, so the measurements rest on the conditions present when each thermogram was taken.

Capture used a radiometric thermal camera and a matched visual camera on a drone, with survey-grade RTK positioning. Detailed capture was flown at 30 m above the modules, with an overview at 50 m used only for orientation and triage. Reflected apparent temperature was measured on site from a sky thermogram, and emissivity was set for glass at the viewing angle the 30 degree tilt produces. Irradiance was read with an irradiance meter, both flat and in the plane of the array.

Every thermogram was analysed and classified by our Level 3 Master Thermographer: the anomaly type, a severity band on the measured temperature difference, a consequence (Safety, Yield or Degradation Trajectory) and the matching IEC 62446-3:2017 condition. Each finding was located by row and column on a grid reference for its zone, which the client can use directly on site.

• Included: detailed aerial thermography of all seven zones, analysis and classification of every thermogram, a findings table, annotated thermogram pages and a signed Level 3 report.
• Included: a grid reference for each zone, locating every finding by row and column.
• Excluded: electrical testing, string testing and any access to inverters or switchgear.
• Excluded: modules shaded by trees or undergrowth, which cannot be assessed thermally and are recorded as such.