A solar panel hotspot is a localised area of excessive heat on a photovoltaic module — caused by a cell or group of cells dissipating energy as heat instead of producing electricity. Hotspots are the leading cause of solar panel fires in India and can permanently damage panels within weeks of developing. Yet they are invisible to the naked eye and undetectable without thermal imaging.
What Causes Solar Panel Hotspots?
- Partial shading — even a small shadow forces the shaded cell to act as a resistor, generating heat
- Cell cracks — micro-cracks from hail, transport damage, or thermal stress reduce cell efficiency
- Bypass diode failure — a failed bypass diode forces current through an unhealthy string
- Soiling — bird droppings, dust, or leaf debris creates localised shading
- Manufacturing defects — poor cell interconnection or paste application creates hot spots from day 1
- Snail trails — silver paste oxidation creates visible brown patterns and localised heating
- PID (Potential Induced Degradation) — voltage leakage causes systematic performance loss with heating
How Dangerous Are Hotspots?
Hotspots with a temperature difference (ΔT) above 40°C vs surrounding modules are classified as Critical under IEC 62446-3:2022. At these temperatures, encapsulant delamination, glass cracking, and junction box fires are real risks. India sees 200–300 reported solar plant fires per year — the majority caused by electrical faults including hotspots.
| ΔT (vs ambient) | Risk Level | Action |
|---|---|---|
| Below 10°C | Low | Monitor at next scheduled inspection |
| 10°C – 40°C | Moderate | Repair within 1 month |
| Above 40°C | Critical — Fire Risk | Immediate shutdown and replacement |
How Drone Thermal Imaging Detects Hotspots
A thermal drone equipped with a calibrated radiometric infrared camera can detect temperature differences as small as 0.05°C. Flying at 30–50 metres altitude, it captures the thermal signature of every module in the plant. Hotspots appear as bright areas in the thermal image — immediately distinguishable from normal operating cells. A single drone can inspect 5–10 MW of solar panels per day.
What Happens After Hotspot Detection?
- Critical hotspots (ΔT > 40°C) → Immediate notification to plant operator
- GPS coordinates provided for ground team to locate exact module
- Severity report helps maintenance team prioritise replacement schedule
- Before/after re-inspection available to confirm repairs resolved the issue
- IEC-compliant report used for insurance claims or warranty replacement
How to Prevent Hotspots
- Annual drone thermal inspection to catch hotspots before they worsen
- Regular cleaning schedule — especially in dusty regions like Rajasthan and Gujarat
- Install shade-free layouts during project planning
- Use half-cut cell modules — more resistant to partial shading hotspots
- Monitor string-level performance via SCADA for early warning
Frequently Asked Questions
Can I detect hotspots without a drone?
Handheld thermal cameras can detect hotspots but are slow, miss panels that are hard to reach, and create inconsistent coverage. Drone inspection covers 100% of modules systematically in a fraction of the time.
Does a hotspot automatically void the module warranty?
It depends on the cause. Manufacturing-related hotspots (cell cracks from production) are typically covered. Hotspots caused by external damage (hail, soiling) may not be. An IEC-compliant EL + thermal report is required for any warranty claim.
How quickly can Varuna Aerotech respond to a critical hotspot finding?
We provide same-day verbal notification for critical findings during inspection. Written report with GPS coordinates is delivered within 24 hours for emergency situations.
