How to Detect Hotspots in Solar and PID Effects in PV Modules to Prevent Long-Term Losses?

Hotspots in Solar and PID Effects in PV Modules: In the world of solar energy, photovoltaic (PV) modules are at the heart of every system. However, their performance can be silently compromised by two major issues: hotspots and Potential Induced Degradation (PID). If left undetected, these problems can lead to significant energy losses and costly replacements.

Whether you’re a homeowner, installer, or solar project manager, understanding how to identify and prevent these hidden threats is key to maintaining long-term efficiency and ROI.

What Are Hotspots in Solar Panels?

Hotspots are localized areas on a solar panel that become significantly hotter than the surrounding cells. These are caused by:

Shading from leaves, bird droppings, or dirt
Manufacturing defects
Cracked or damaged cells
Faulty bypass diodes

Hotspots force some cells to absorb rather than produce energy, turning them into resistive loads. Over time, this can degrade the panel’s surface, reduce efficiency, or even lead to fire hazards.

How to Detect Hotspots?

Infrared (IR) Thermography
A thermal camera can easily identify temperature anomalies in a panel. IR images highlight hotspots in real-time, making them ideal for large-scale solar farm inspections.
Visual Inspection
Discoloration, burn marks, or bubbling on the panel’s surface may indicate long-term hotspot damage.
I-V Curve Analysis
A deviation in the I-V curve can indicate mismatch issues and potential hotspots. This test helps pinpoint affected strings or modules.

What is PID (Potential Induced Degradation)?

PID is a degradation phenomenon caused by high voltage stress between the solar cells and the grounded frame or glass surface. It leads to leakage currents and reduced output.

Common causes include:

High system voltage (>1000V)
Poor-quality encapsulation or glass
High ambient temperature and humidity

Unlike hotspots, PID can affect entire modules or strings, often without visual symptoms.

How to Detect PID?

Electroluminescence (EL) Imaging
EL cameras can visualize internal cell damage, revealing PID-affected areas even before energy output drops.
Voltage & Power Drop Monitoring
A gradual decline in output, especially in strings under high voltage stress, may signal PID onset.
Insulation Resistance Testing
This test checks leakage currents that may indicate PID, especially useful in large installations.

Prevention & Mitigation Tips

Use PID-resistant modules from reputable manufacturers
Ensure proper grounding and insulation
Maintain low system voltages where possible
Install PID recovery devices if degradation is detected
Regularly clean panels to prevent shading and hotspots

Final Thoughts

Ignoring hotspots or PID can lead to 5–30% energy loss annually a major setback for both rooftop and utility-scale projects. Early detection and proactive maintenance are essential to keep your solar system performing at its best.

If you’re investing in solar, regular health checks of your PV modules aren’t just an option they’re a necessity.

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