The temperature coefficient significantly impacts the long-term energy production of solar panels by quantifying how much their power output decreases as the panel temperature rises above the standard testing condition of 25°C (77°F).
What is the Temperature Coefficient?
- The temperature coefficient is expressed as a negative percentage per degree Celsius (%/°C) and represents the percent loss in panel efficiency or power output for every 1°C increase in temperature above 25°C. For example, a temperature coefficient of -0.4%/°C means the panel loses 0.4% of its power output for each degree Celsius above 25°C.
- Solar panels are tested at 25°C, but in real-world conditions, panel temperatures often reach 50°C or higher, especially in hot climates. This temperature rise can cause substantial power losses.
How Temperature Coefficient Affects Long-Term Energy Production
- Since solar panels operate outdoors under direct sunlight, their temperature often exceeds 25°C, sometimes reaching up to 65°C or more. Power output declines as temperature increases due to intrinsic properties of the silicon cells. For example, a panel with a temperature coefficient of -0.4%/°C operating at 65°C (a 40°C increase) would lose approximately 16% of its rated power output at STC (Standard Test Conditions).
- Over time, this efficiency loss due to heat reduces the total energy generated by the solar panel system, especially in hot climates where panels consistently operate at elevated temperatures.
- Lower temperature coefficient values (i.e., closer to zero) indicate better performance at high temperatures. For instance, panels from brands like REC Group and Panasonic have temperature coefficients around -0.24%/°C, which means less efficiency loss compared to panels with coefficients near -0.5%/°C.
- Advances in panel technology, such as the use of thermally conductive substrates and panel mounting techniques that allow airflow and cooling, help mitigate temperature-related losses.
Practical Implications
- In cooler climates, temperature coefficient may not be a major concern since panel temperatures are closer to the optimal 25°C, and efficiency losses are minimal.
- In hot environments, selecting panels with a lower temperature coefficient can improve long-term energy yield by reducing heat-induced efficiency losses.
- Roofing materials and installation methods also influence panel temperature and thus energy production. Reflective roofs and mounting methods that promote cooling can reduce operating temperatures and improve panel output.
Summary Table of Temperature Coefficients for Common Panels
| Brand | Typical Temperature Coefficient (%/°C) |
|---|---|
| REC Group | -0.24 |
| Panasonic | -0.24 to -0.29 |
| Maxeon | -0.27 to -0.38 |
| SunPower | -0.29 to -0.38 |
| Q CELLS | -0.37 to -0.42 |
| Polycrystalline panels | Around -0.41 to -0.50 |
Conclusion
The temperature coefficient is a key factor in determining the long-term energy production of solar panels, especially in hot climates. Panels with lower (less negative) temperature coefficients suffer less performance degradation as temperatures rise, thereby producing more energy over their lifetime. Considering temperature coefficients alongside other factors like panel efficiency, installation type, and local climate is essential for optimizing solar energy yield.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-temperature-coefficient-impact-the-long-term-energy-production-of-solar-panels/
