The electricity generation capability of a solar photovoltaic (PV) module is directly influenced by its temperature. This influence is expressed through the temperature coefficient. Stated as a percentage, the solar panel temperature coefficient represents the decline in production with each 1° Celsius rise in temperature above 25° C.
Standard Test Conditions (STC) require solar PV modules to be tested for efficiency at a cell temperature of 25° C. Additionally, it is important to take into account that for every increase of 2° C above 25° C, there will be power losses of approximately 1%. Solar PV modules usually have a temperature coefficient ranging from -0.3% / °C to -0.5% / °C.
Effect of Solar Panel Temperature Coefficient
While a solar panel temperature coefficient is not the sole determinant of its power output, it does serve as a valuable reference point for accurately estimating the actual level of production for them. Even on the hottest summer day, the decrease in efficiency of solar panels is usually insignificant, unless they are subjected to an excessive amount of heat.
If your roof absorbs a lot of heat, and you live in a place where summer temperatures often reach 110° Fahrenheit or higher, you will lose more energy, but it won’t have a significant impact on your long-term energy savings.
When planning your solar system, it’s important to be cautious about placing panels on top of a heated vent to avoid any potential issues that may arise.
Calculation of Temperature Coefficient
Let us take an example, to calculate the power loss of a solar PV module.
The ambient temperature in the region is 28° C
Installed on a Typical Rack-Type installation the panel temperature is 30° C
Therefore, overall panel temperature = 28 + 30 = 58° C
The panel wattage is 450W.
The temperature at maximum output power (Pmax) at Nominal Module Operating Temperature (NMOT) is -0.35%/°C
With solar module temperature reaching 58° C which is the total ambient temperature and panel temperature on racks.
Thus, power loss = 58° C – 25° C = 33° C (temperature difference between the module’s Pmax at NMOT and the hypothetical example temperature of 58° C reached by the cells)
Now, it shows that the module loses 33° C ×— (-0.35%) = 11.55% power output when the temperature of the cells is around 58° C.
Therefore, solar module power loss = -11.55% ×— 450W = -51.98W. Thus, this module will operate at 58° C with a max power of 450 – 51.98 = 398.02W.
