Hot Spot Detection Test in Solar PV Modules | Process, Purpose & IEC 61215 Criteria The Hot Spot Detection Test is a crucial reliabi...
Hot Spot Detection Test in Solar PV Modules | Process, Purpose & IEC 61215 Criteria
The Hot Spot Detection Test is a crucial reliability and safety test for solar PV modules, designed to identify areas within a module that experience excessive local heating — known as hot spots.
Hot spots occur when a portion of a solar cell or group of cells operates under reverse bias due to shading, cell defects, or mismatches. These areas can heat up significantly, potentially damaging the module and reducing overall performance.
⚙️ Purpose of the Test
To ensure that the solar module design and cell interconnection can withstand localised heating effects without causing damage or permanent performance degradation.
It helps in verifying:
- The thermal stability of solar cells and interconnections
- The quality of bypass diodes
- The module’s resistance to localised stress under partial shading or mismatch conditions
🧪 Test Procedure
The module is first stabilised under Standard Test Conditions (STC) to ensure consistent starting parameters.
Identification of the Weakest Cell/Area:
The module is analysed to identify the cell or region that exhibits the lowest short-circuit current (Isc); this cell will likely develop a hot spot under reverse bias.
Partial Shading Simulation:
Artificial shading or reverse biasing is applied to the identified cell to simulate real-world conditions like dirt, leaf cover, or bird droppings.
- The temperature rise in the affected area is measured using infrared (IR) thermography or thermal sensors.
- Electrical characteristics are monitored to record any changes in performance.
The module is exposed for a defined time (as per IEC 61215 or IS 14286 standards) while ensuring temperatures remain within permissible limits.
The module is visually and electrically inspected for any:
- Burn marks or delamination
- Discoloration of encapsulant
- Cracks or glass damage
- Power loss beyond acceptable limits
📏 Acceptance Criteria
According to IEC 61215 standards:
- The maximum temperature difference between the hot spot and the average module temperature should not exceed 20–30°C (depending on module type).
- The module must not exhibit any visible damage or power degradation greater than the standard allowable limit (typically ≤ 5%).
⚡ Common Causes of Hot Spots
- Cell mismatch due to manufacturing variation
- Microcracks or mechanical stress in cells
- Defective bypass diodes
- Shading from dirt, bird droppings, or nearby objects
- Soldering defects leading to poor current flow
🧠 Importance of Hot Spot Detection
- Ensures safety and longevity of solar PV modules
- Detects latent manufacturing or installation defects
- Prevents thermal runaway and potential fire risks
- Maintains high efficiency and consistent field performance
The Hot Spot Detection Test is one of the most critical reliability tests in the solar industry.
It not only protects the module from thermal degradation but also safeguards system reliability and investor confidence.
A module that passes this test demonstrates robust design, proper cell matching, and superior thermal management — all essential for long-term solar plant performance.
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