Hotspots in Solar Panels: Invisible Threats to Solar Efficiency

Hotspots are localized regions on a photovoltaic (PV) module that exhibit significantly higher temperatures than the surrounding areas. These temperature anomalies are often invisible to the naked eye but can have serious implications for the module's electrical performance, reliability, and safety. Hotspots are widely regarded as one of the most persistent and detrimental forms of performance degradation in solar panels, often arising from shading, cell mismatch, etc.

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While the average surface temperature of a module under standard operating conditions might range between 45-70°C, hotspot regions can exceed 100°C, potentially damaging cell interconnections, encapsulants, or even causing module burnout in extreme cases. These thermal imbalances not only reduce the power output but can also shorten the lifespan of a PV system.

Causes of Hotspot Formation

Hotspots typically originate from partial obstructions or inconsistencies within a module that force certain cells or cell regions to operate in reverse bias, thereby dissipating power as heat instead of generating electricity.

Shading Effects

One of the most common causes is partial shading due to nearby objects like trees, poles, or dirt accumulation. When a cell in a series string is shaded, it acts as a resistive load, heating up while the rest of the string continues to drive current through it.

Cell Mismatch

Variations in electrical properties among cells, degradation, or microcracks—can result in uneven current flow. Cells with lower current generation capacity become bottlenecks, and under forced current, dissipate excess energy as heat.

Defective Bypass Diodes

Bypass diodes are intended to protect shaded or underperforming cells by redirecting current flow. A failed or incorrectly functioning diode can leave a cell vulnerable to reverse bias operation, intensifying local heating.

Manufacturing Defects

Localized impurities, edge isolation failures, poor soldering, and broken interconnect ribbons can introduce electrical discontinuities or elevated series resistance—both of which are conducive to hotspot development.

Impact on Performance and Safety