Thermal Imaging Workflow¶
ACTIVE SOP
Thermal imaging is one of the most powerful diagnostic tools in solar field work. It reveals problems invisible to the naked eye — hot cells, bypassed bypass diodes, connection resistance, underperforming strings.
When to Use Thermal Imaging¶
- Annual O&M inspections (full array scan)
- Investigating underperforming strings or modules
- Post-storm damage assessment
- Warranty documentation for manufacturer claims
- Any complaint of burning smell or unusual heat
Optimal Conditions¶
Condition Requirements
Thermal imaging of solar panels only works under these conditions:
- Irradiance ≥ 600 W/m² — overcast conditions reduce contrast and mask defects
- Array producing power — panels must be generating current for heat anomalies to appear
- Steady-state — best results 2+ hours after sunrise, before late afternoon shadow changes
- Minimal wind — wind cools anomalies and can obscure findings
- Camera warm-up — allow 5–10 minutes before use
Equipment¶
- FLIR camera or FLIR phone attachment (preferred)
- Alternatively: any IEC 62446-3 compliant thermal camera
- Standard phone camera for documentation alongside thermal
Scanning Sequence¶
From Ground Level (when possible)¶
- Begin at one corner of the array
- Work systematically — row by row, string by string
- Capture each module at consistent angle (30–45° off-normal preferred)
- Flag any anomaly with a standard photo alongside the thermal photo
From Roof Level¶
- Walk along roof edge or access path
- Scan each row systematically
- Do not walk across the array — scan from adjacent structure or edge
- For ground-mount: walk the perimeter, then the row paths
Temperature Delta Interpretation Guide¶
| Delta T (°C above ambient modules) | Likely Finding | Priority |
|---|---|---|
| < 3°C | Normal variation or noise | Monitor |
| 3–10°C | Cell mismatch, partial shade, mild soiling | Investigate |
| 10–20°C | Bypass diode activation, significant soiling, cell failure | Address soon |
| > 20°C | Serious cell failure, internal arc, connection resistance | Address immediately |
| Hot spot (single cell, very high) | Cracked cell, delamination, internal short | High priority — document for warranty |
Documentation Requirements¶
For every thermal finding:
- Thermal image (clearly showing the anomaly)
- Standard visible-light photo of the same panel (for identification)
- Note: row/column position or string ID
- Estimate of delta T
- Describe the pattern (full module, single cell, corner, edge, center)
Common Findings in the Field¶
- Hot strings — one string hotter than others → string fault or optimizer issue
- Hot rows within a string — bypass diode activated, shade mismatch, or cell failure
- Single hot cell — cracked cell or delamination → warranty candidate
- Hot junction box — internal arc or failed bypass diode → replace module
- Hot combiner input — connection resistance, loose terminal