The temperature coefficient of a solar panel quantifies how much the panel’s power output decreases as its temperature rises above the standard test condition temperature of 25°C. It is expressed as a percentage loss in efficiency per degree Celsius increase in temperature.
How Temperature Coefficient Affects Solar Panel Performance
- Negative Impact on Efficiency: Most solar panels have a negative temperature coefficient, typically ranging from about -0.3% to -0.5% per °C. This means that for every 1°C increase in temperature above 25°C, the panel’s efficiency decreases by roughly 0.3% to 0.5%.
- Example: If a solar panel has a temperature coefficient of -0.37%/°C and operates at 35°C, it will lose approximately 3.7% efficiency compared to its rated output at 25°C. For instance, a panel rated at 17% efficiency at 25°C would perform closer to 16.4% at 35°C.
- High Temperatures Lead to Significant Power Loss: Real-world operating temperatures can often be 20-30°C higher than ambient conditions, sometimes reaching 60-70°C on hot summer days. At such temperatures, power loss can be substantial. For example, a module with a -0.41%/°C coefficient at 65°C (which is 40°C above 25°C) could suffer around a 16.4% reduction in power output.
- Voltage Decrease Drives Power Loss: The temperature increase causes the voltage output of silicon cells to drop more than the current increases, resulting in an overall net loss of power.
Factors Influencing the Temperature Coefficient and Panel Temperature
- Panel Technology: Different types of solar panels have different temperature coefficients:
- Monocrystalline and polycrystalline silicon panels usually have coefficients between -0.3% and -0.5%/°C.
- High-quality panels like SunPower or Maxeon often have better (less negative) coefficients around -0.29% to -0.38%/°C.
- Thin-film panels generally have lower temperature coefficients (around -0.2%/°C), meaning they lose less efficiency as temperature rises.
- Installation Type and Roofing Material: How and where panels are installed affects their operating temperature.
- Angled roof mounts tend to be cooler than flat mounts.
- Roof materials that absorb less heat (like metal or light-colored shingles) help keep panels cooler.
- Dark or heat-absorbing roofing materials increase panel temperature, worsening power losses.
Importance of Temperature Coefficient for Solar Projects
- Panels with lower (less negative) temperature coefficients are advantageous in hot climates or during summer months since they maintain higher efficiency under elevated temperatures.
- A lower temperature coefficient contributes to:
- Improved and more consistent energy production.
- Longer panel lifespan due to reduced thermal stress.
- Better return on investment by generating more electricity over time.
- While the temperature coefficient is just one factor affecting overall panel performance, it is critical for accurately estimating realistic energy yields, especially in warm or sunny regions.
Summary Table of Temperature Coefficients by Panel Type:
| Panel Type | Typical Temperature Coefficient (%/°C) |
|---|---|
| SunPower / Maxeon | -0.29% to -0.38% |
| LG / Panasonic | -0.3% to -0.42% |
| Q CELLS / Hyundai | -0.37% to -0.45% |
| Thin-film Solar Panels | Around -0.2% |
| Average Crystalline | -0.3% to -0.5% |
In conclusion, temperature coefficients directly influence solar panel efficiency by quantifying how much output drops as temperature rises. Understanding and selecting panels with favorable temperature coefficients can significantly improve system performance and reliability in high-temperature environments. This is especially relevant in regions with hot climates, where panel temperatures regularly exceed standard testing conditions.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-do-temperature-coefficients-affect-the-performance-of-solar-panels/
