Factors Affecting Solar Panel Lifetime

1. Degradation

• Degradation is the gradual loss of output over time. According to the National Renewable Energy Laboratory (NREL), the average annual degradation rate is about 0.5%. Some premium manufacturers offer lower rates, as little as 0.3%.
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• – Potential Induced Degradation (PID): Affects some panels due to ion movement within the module. PID-resistant materials can mitigate this.
• – Light-Induced Degradation (LID): Initial efficiency loss within the first hours of sun exposure. LID typically ranges from 1-3%.

2. Weathering

• Exposure to weather is a primary driver of degradation. Key elements include:
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• – Heat: Negatively affects performance. Panels have a temperature coefficient indicating efficiency loss per degree above 25°C. For example, a -0.35% coefficient means 0.35% efficiency loss per additional degree Celsius.
• – Thermal Cycling: Causes microcracks due to expansion and contraction with temperature changes.
• – Wind: Strong winds can flex panels, leading to microcracks. Use racking solutions for high-wind areas.
• – Snow: Can cover panels and cause mechanical load. Use care when removing snow to avoid scratching.
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• Proper installation techniques, such as elevating panels for airflow and using light-colored materials, can mitigate some of these weather-related effects.

3. Standards

• Adhering to standards ensures longevity and reliability. Key certifications include:
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• – IEC 61215: Tests for electrical characteristics, mechanical load, and climate resilience.
  – Underwriters Laboratories (UL): Conducts climactic and aging tests to ensure safety and durability.

4. Failures

• Solar panel failures are rare. NREL’s study of over 50,000 systems showed a median failure rate of 5 panels per 10,000 annually. Most system downtimes are due to inverter failures, not panel failures.