What are PV module hot spots, its causes and effects?

Hot spots are areas of high temperature that affect only one zone of the solar panel and resulting in a localized decrease in efficiency, and therefore, lower output power and accelerated material degradation in the area affected by the high temperature. Hot spots are not visible to human eyes and are detected and verified using infrared measurement technique.
Above image shows of a solar panel showing a hot spot developed due to bird droppings

Causes and its effects

The reasons for the appearance of hot spots are multiple and can be classified into functional or operational. Defect severity and remediation actions also vary widely as a result.

Functional reasons

  • Cell mismatch: It occurs when cells of different current are connected in series.
  • Cell damage: It occurs during manufacture, due to the fact that the silicon cell will be subjected to a stressful process during rolling, handling and transportation.

Operational reasons

  • Seasonal shadows: When cells are completely or partially shaded for a long period of time, it results in increased temperature in the shaded cell and further creates hot spots. The loss in power output due to a hot spot in solar panels is not directly correlated with the area of the panel that is shadowed. Even a small shade can have a significant impact on the output power of the module.
  • Soiling or dirt accumulation: Solar panels become dirty from dust, suspended sand, dirt and other contaminating impurities if not cleaned periodically during their service life. The dust accumulated on the glass and corners if not cleaned over a period of time may result in increased temperature in the shaded cell which can lead to the hot spot, therefore such a situations should be avoided.

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