Factors Affecting Durability1. Environmental ConditionsExternal conditions directly influence the longevity and efficiency of poly-crystalline panels:· Temperature Coefficients: Generally, poly panels are in the range of -0.4 to -0.5% per 째C. This means that above 25째C, it loses 0.4-0.5% efficiency with each degree upwards. For instance, if a panel surface temperature goes to 65째C in desert countries like Saudi Arabia, there could be losses of over 20%.· Snow and Hail Impact: Areas that receive snowfall and hail can inflict physical damage. Newer poly panels are tested to resist hailstones as large as 25 mm in diameter at 23 m/s.· Humidity and Salinity: The rate of corrosion is very fast in coastal areas. Poly panels with IP67-rated junction boxes and corrosion-resistant frames perform better in high humidity and salinity conditions.2. Material QualityThe quality of raw materials and panel construction significantly influences durability. Key aspects include:· Silicon Purity: High-grade silicon improves energy output and reduces internal resistance, ensuring long-term efficiency. Poly panels with silicon purity levels of 99.999% (5N) demonstrate lower degradation rates.· Encapsulation: The cells are encapsulated in layers of ethylene vinyl acetate (EVA) and tempered glass to protect them from moisture and UV radiation. High-transmittance glass in panels increases the absorption of light by about 2%.· Backsheet and Frame Durability: Long-lasting backsheets and aluminum frames with a mechanical load rating of 5400 Pa offer structural integrity and prevent damage from wind and snow loads.3. Installation StandardsOther leading causes of premature degradation include poor installation practices. Specific factors include:· Mechanical Stress: Erroneous mounting of panels generates microcracks, further degrading efficiency up to 15% in a very short period of time.· String Configuration: A wrong configuration in the DC strings leads to bypass heating and mismatch losses at bypass diodes.· Angle and Orientation: The tilt angle will depend upon latitude. For northern Europe, for example, an inclination of 35-40째 is believed to be ideal, while 10-15째 can work for equatorial areas.
