Know what the camera measures

A thermal camera detects infrared radiation and converts it into a temperature estimate using measurement assumptions. It does not look through a module to identify every internal fault. Surface properties, reflected radiation, atmospheric effects and camera configuration influence the estimate. Treat a displayed temperature as a measurement with conditions and uncertainty, not an unquestionable number.

Radiometric files retain information needed for later temperature analysis. A rendered image may preserve only the chosen colours and annotations. Keep both the original data and a readable export, together with camera details and processing settings. If only a screenshot is available, state that limitation explicitly rather than implying that a complete quantitative analysis has been performed.

Read the operating conditions first

Solar loading affects how some abnormalities become visible. Wind can cool the surface, while clouds can change irradiance during a flight. A pattern recorded after a sudden change may not be comparable with an image acquired under stable conditions. Check the timing and representativeness of weather measurements rather than assigning a single daily weather description to the entire dataset.

The electrical state also matters. A disconnected section and an operating section may exhibit different thermal behaviour for reasons unrelated to a new defect. Check inverter availability, curtailment, known outages and any relevant switching records. For trackers, orientation and self-shading can change during the survey. Thermal interpretation should be connected to those records wherever they are available.

Separate a pattern from a cause

A localised warm region may be consistent with a cell-level concern, but competing explanations can include partial shading or contamination. A substring-shaped pattern may suggest a different mechanism, while a whole-module or string pattern may require a wider system check. These are useful organising observations, not one-to-one diagnostic rules.

Use visible imagery to look for debris, vegetation, surface damage and nearby objects. Compare neighbouring modules of similar construction and operating state. A sensible comparison is not simply the coolest pixel in the image: it is a relevant reference under sufficiently similar conditions. Record how the reference was chosen so another reviewer can assess whether the comparison was fair.

Challenge reflections and viewing geometry

Module glass can reflect the sky, surrounding structures or the aircraft. A reflected feature may appear dramatic without representing a real temperature rise at the apparent location. Where safe and appropriate, a different viewing geometry can help test that explanation. Look for patterns that move, distort or change relative to the module as the viewing angle changes.

Oblique views can also reduce useful spatial detail. A small cell-level feature may occupy too few pixels for reliable interpretation. Focus, distance and motion matter even when the colour contrast looks strong. Reject or qualify images that cannot support the claim being made; adjusting the colour palette cannot restore missing detail.

Avoid universal temperature shortcuts

A single temperature-difference threshold cannot account for every module technology, operating condition, fault mechanism and site risk. Any classification method should define its measurement approach, applicable conditions, uncertainty and escalation logic. IEC 62446-3 is a relevant reference for outdoor infrared thermography; project requirements and competent interpretation still matter.

Likewise, a thermal contrast does not directly equal an annual energy loss. Estimating production impact requires an appropriate model and supporting operational evidence, with assumptions made explicit. Do not convert a visually striking hot spot into a precise savings claim simply because a reporting platform offers a field for one.

Turn the interpretation into a testable next step

A good thermal report states what was observed, how the image was captured, which alternatives were considered and what would resolve the remaining uncertainty. The next step might be repeat imaging under comparable conditions, a visible inspection, a review of monitoring data or a targeted electrical investigation by qualified personnel.

If the finding suggests a potential safety issue, follow the site’s escalation process rather than waiting for perfect classification. The role of thermal screening is to direct attention and preserve evidence. The decision to isolate equipment, undertake electrical testing or replace a component belongs within a competent, authorised maintenance process.

Sources and further reading

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