The temperature coefficient of a solar panel quantifies how much the panel’s efficiency and power output decrease as its temperature rises above the standard test condition of 25°C (77°F). It is usually expressed as a negative percentage per degree Celsius (%/°C), indicating a drop in performance for each degree the panel temperature exceeds 25°C.
How Temperature Coefficient Affects Solar Panel Efficiency
- Negative Impact of Heat on Efficiency: Solar panels are tested at 25°C, where they achieve their rated efficiency. However, in real-world conditions, panels often operate at much higher temperatures, sometimes reaching 50°C or more. As temperature increases, the panel’s voltage decreases more significantly than the current increases, causing an overall power loss. This means efficiency drops as panel temperature rises.
- Typical Temperature Coefficients: Most crystalline silicon solar panels have temperature coefficients between approximately -0.29%/°C and -0.5%/°C. This means for every degree Celsius above 25°C, the panel’s output drops by roughly 0.3% to 0.5% of its rated power.
- Example of Efficiency Loss: For a panel with a temperature coefficient of -0.41%/°C, if the panel temperature reaches 65°C (40°C above 25°C), the power loss can be around 16.4%. For instance, a 260W panel would lose about 42.6W under these conditions, operating at an effective maximum power of 217W. Similarly, a high-efficiency panel with a coefficient of -0.24%/°C might see its efficiency decline from 22.2% to about 21.7% when the temperature rises from 25°C to 35°C.
- Panel Technology Differences: Thin-film panels generally have lower temperature coefficients (closer to -0.2%/°C), making them less sensitive to heat compared to monocrystalline or polycrystalline silicon panels, which often are in the range of -0.3% to -0.5%/°C. Maxeon panels, for example, have better (lower) coefficients (~-0.38%/°C) compared to typical crystalline panels.
- Environmental and Installation Factors: The actual operating temperature of panels depends on factors such as ambient air temperature, mounting style, roofing material, and airflow beneath the panels. Dark-colored roofs can increase panel temperatures, causing more efficiency loss. Proper mounting techniques that allow airflow and reflective roofing materials can help mitigate temperature-related losses.
Overall Efficiency Impact
- The temperature coefficient directly influences the overall energy yield of solar panels, especially in hot climates or during summer months when panel temperatures rise significantly above 25°C.
- Although the percentage decrease per degree may seem small, the cumulative effect over many degrees can substantially reduce the panel’s annual energy production.
- This makes the temperature coefficient a critical factor to consider when selecting panels for regions with high ambient temperatures or intense solar radiation.
- Conversely, in cooler climates, the temperature coefficient is less critical, as panels tend to operate closer to or below the 25°C reference point, where efficiency is maximized.
Summary Table of Typical Temperature Coefficients
| Panel Type/Brand | Temperature Coefficient (%/°C) | Effect on Efficiency |
|---|---|---|
| REC Group Alpha Pure | -0.24% | Lower efficiency loss with heat |
| Panasonic Evervolt HK2 | -0.24% | Lower efficiency loss with heat |
| Maxeon Monocrystalline | ~-0.38% | Better than average crystalline panels |
| Q CELLS | -0.37% to -0.42% | Moderate heat sensitivity |
| Thin Film Panels | ~-0.2% | Least affected by heat |
| Typical Crystalline | -0.3% to -0.5% | Average heat sensitivity |
In conclusion, the temperature coefficient significantly impacts the overall efficiency of solar panels by quantifying the reduction in output power as temperature rises above 25°C. Selecting panels with lower temperature coefficients and optimizing installation to reduce operating temperatures can mitigate efficiency losses, especially in hot climates.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-temperature-coefficient-affect-the-overall-efficiency-of-solar-panels/
