The temperature coefficient significantly affects solar panel performance by quantifying how much a solar panel’s power output decreases as its temperature rises above the standard testing condition of 25°C (77°F). This coefficient is typically expressed as a negative percentage per degree Celsius (%/°C), indicating the fraction of power lost for each degree rise in temperature.
How Temperature Coefficient Affects Solar Panel Performance
- Power Output Reduction: The temperature coefficient defines the rate at which a solar panel’s efficiency drops as temperature increases. For example, a temperature coefficient of -0.38%/°C means that for every 1°C increase above 25°C, the panel loses 0.38% of its power output; conversely, efficiency increases by the same amount for each degree below 25°C.
- Typical Range: Most crystalline silicon panels have temperature coefficients between about -0.3% and -0.5% per °C. High-quality panels like SunPower’s range from around -0.29% to -0.38%/°C, while thin-film panels can have lower coefficients (~ -0.2%/°C), making them more tolerant of heat.
- Real-World Impact: Solar panels frequently operate at temperatures 20-30°C above ambient air temperature, reaching 50-70°C in hot environments. At these elevated temperatures, power losses can reach 3-15% depending on the exact coefficient and temperature rise.
- Physical Cause: Increased temperature reduces the solar cell’s voltage output significantly due to semiconductor physics, mainly by lowering the bandgap energy, increasing recombination rates, and raising internal resistance. While the current output slightly increases with temperature, it doesn’t offset voltage losses, resulting in overall power decline.
- Practical Effect: Although temperature impacts efficiency, the effect is often considered minimal under moderate climates. For instance, a panel at 28°C with a -0.38%/°C coefficient loses only about 1.14% efficiency compared to its rating at 25°C. However, in very hot climates where panels reach 60°C or more, losses can become noticeable, potentially up to 10-15% or more.
Additional Factors Influencing Temperature Effects
- Panel Technology: Monocrystalline and polycrystalline panels generally have higher temperature coefficients (more sensitive to heat) than thin-film technology, which performs better in hot conditions.
- Installation and Mounting: The panel’s orientation, mounting type, and roof material influence operating temperature and thus performance. Roofs that reflect heat (e.g., metal roofs) help keep panels cooler.
- Geographic Location: Solar panels in cooler climates or at higher altitudes usually perform better relative to their rated power because of lower operating temperatures.
Summary Table of Temperature Coefficients for Common Solar Panels
| Solar Panel Type | Temperature Coefficient (%/°C) |
|---|---|
| SunPower (high-efficiency) | -0.29 to -0.38 |
| LG | -0.30 to -0.42 |
| Q CELLS | -0.37 to -0.42 |
| Hyundai | -0.41 to -0.45 |
| Panasonic | -0.29 to -0.30 |
| Thin-film panels | Around -0.2 |
Conclusion
The temperature coefficient is a critical parameter for understanding and predicting how solar panels perform as temperatures vary from the standard testing condition of 25°C. Panels with lower (less negative) temperature coefficients retain more efficiency at higher temperatures, which is particularly important in hot climates. While the efficiency loss per degree may seem small, it can accumulate significantly in extreme heat, making temperature coefficient a key factor when selecting solar panels and estimating their real-world energy production.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-temperature-coefficient-affect-solar-panel-performance/
