Temperature coefficient of performance
The temperature coefficient of performance is a key parameter in the context of photovoltaic (PV) panels, which describes how the performance of these panels changes as a function of temperature. Specifically, this coefficient expresses the percentage change in PV panel performance for each degree Celsius above or below a reference temperature (usually 25°C, which is the standard test value for PV panels).
- Meaning:
At higher temperatures, the performance of PV panels usually decreases. This phenomenon is critical because solar panels can heat up significantly in direct sunlight.
The temperature coefficient of performance provides an estimate of how panel performance will vary in different climates and during different seasons.
- Calculation and units:
The coefficient is usually given as a percentage per degree Celsius (%/°C).
For example, if a PV panel has a temperature coefficient of performance of -0.3%/°C, this means that a 1°C increase in temperature will reduce the panel's performance by 0.3% from its nominal value at 25 degrees.
Suppose the output of a PV panel at 25°C is 100 W and at 35°C is 95 W. The power difference is 5 W, and the temperature difference is 10°C. The temperature coefficient of performance is then (5W/100W)/10°C×100%=0.5
This means that for every degree above 25°C, the panel power drops by 0.5%.
This calculation is important for understanding how panel performance will vary in different climates, and is critical for effective planning and installation of PV systems.