Thermal Inspection of a 462 kW Rooftop Solar Plant

Drone-based thermal and RGB inspection of a rooftop photovoltaic plant in Kaštel Sućurac, Croatia, covering 1,089 half-cut modules to identify thermal anomalies and support performance assessment and maintenance prioritization.

Rooftop462 kWpThermal + RGBIEC 62446-3 Compliant Thermographic InspectionKaštel Sućurac, Croatia2026-08

Hakan Yaralı · Technical Manager

Aerial view of rooftop solar panels with extensive white surface deposits

Project at a Glance

Plant capacity: 462 kWp
Modules inspected: 1,089
Inspection area: ~0.265 ha
Data captured: Thermal + RGB
Inspection duration: 1 field day
Suspected anomalies: 370
Location: Kaštel Sućurac, Croatia
Inspection date: 2026-08
Inspection standard: IEC 62446-3 Compliant Thermographic Inspection

Project Context

The rooftop solar plant in Kaštel Sućurac, Croatia showed extensive surface contamination across a significant portion of the PV modules. This heavy soiling created unfavorable operating conditions and was associated with localized heating across affected areas, making contamination a key factor in both plant performance and maintenance planning. Drone-based thermal and RGB inspection revealed a high occurrence of hotspots and cell faults, particularly on modules affected by visible contamination. By evaluating thermal anomalies together with RGB evidence, the inspection helped identify the most affected modules, assess their impact on energy production, and prioritize cleaning and maintenance activities based on operational and financial impact.

Inspection Scope

What was inspected

Thermal and RGB imagery across the entire rooftop photovoltaic array
1,089 half-cut Trina Varius photovoltaic modules
Assessment of heavy surface contamination and soiling intensity across the inspected modules
AI-assisted anomaly screening at module level
Detection and classification of hotspot and cell anomalies, particularly in areas affected by visible contamination
Cross-assessment of thermal findings with RGB observations to evaluate the relationship between soiling and localized heating
Technical review of identified anomalies
Prioritization based on estimated operational, efficiency, and financial impact

Methodology

1
Pre-flight planning
Flight altitude was defined to achieve a 3 cm/pixel GSD in accordance with IEC 62446-3 requirements, while overlap and flight route were planned according to the plant layout.
2
RGB and thermal data acquisition
Thermal and RGB imagery was captured across the inspected photovoltaic array.
3
Image quality control and alignment
Coverage and thermal image integrity were checked and imagery was georeferenced for analysis.
4
AI-assisted anomaly screening
Thermal patterns were detected, grouped and mapped to individual photovoltaic modules.
5
Technical review
Detected findings were reviewed and classified according to their thermal characteristics.
6
Reporting and verification plan
Prioritized findings were delivered to the client together with efficiency and loss-impact assessments to support subsequent maintenance activities.

Findings

Finding	Detected pattern	Possible cause	Verification	Status
Hotspot	A localized area reaches an abnormally high temperature compared with its surroundings.	Cell damage, microcracks, physical defects, shading, contamination, or other conditions that cause abnormal localized heating.	Thermal measurement and visual inspection: reported; further field verification may be required.	Pending
Cell Fault	A PV cell loses normal function, causing localized heating and reduced performance.	Manufacturing defects, microcracks, physical damage, or deterioration of the affected cell.	Thermal measurement and visual inspection: reported; further field verification may be required.	Pending
Multicell Fault	Multiple PV cells within the same module lose normal function, causing wider performance and power loss.	Manufacturing defects, thermal stress, or physical damage affecting multiple cells within the module.	Thermal measurement and visual inspection: reported; further field verification may be required.	Pending

Thermal Evidence

Grayscale thermal view of rooftop solar panels with scattered bright patches — Thermal and RGB views of rooftop modules in Kaštel Sućurac, showing visible surface contamination and localized heating. RGB observations such as contamination or vegetation may coincide with thermal findings but should not automatically be considered the confirmed cause of the anomaly. Additional field verification may be required to determine the underlying root cause.

Actions and Outcome

A total of 370 anomalous modules were identified and reported to the client. This comprises 268 hotspot findings and 122 cell faults, 390 findings in all; 20 modules show both, so the findings affect 370 distinct modules.
The highest concentration of hotspot and cell anomalies was observed on modules with heavy surface contamination, indicating that severe soiling was a key condition affecting thermal performance across the site.
Modules with more intensive contamination showed stronger localized heating and a higher occurrence of thermal anomalies, making these areas a priority for cleaning and maintenance.
The additional efficiency loss and estimated financial impact associated with the affected modules were calculated to support maintenance prioritization.
Findings were prioritized according to their estimated impact on plant efficiency, energy production, and financial loss, helping the client focus corrective actions on the most affected areas first.

Limitations

Thermal imagery can identify temperature patterns requiring investigation, but it does not independently confirm every electrical or mechanical root cause. Irradiance, wind, reflections, shading, soiling, flight conditions and equipment configuration may affect interpretation.