Voc gets reduced when decreasing temperature

[Dominik Damberger]

Hey,

please take a look at the following three screenshots. From -15°C to -20°C the Voc value gets reduced. Is this supposed to happen? I was under the impression that the lower the temperature the higher the Voc value gets.

 

BR and thanks,

Dominik

[Linda Thoren]

Dear Dominik Damberger

In most cases, the open-circuit voltage (Voc) of a PV module will increase as the temperature decreases. This phenomenon is known as the temperature coefficient of voltage, and it's a fundamental characteristic of solar panels. However, at very cold temperatures, such as those below -20°C, will have adverse effects on the performance of a PV module because of mechanical stress on the components etc. The Temperature coefficient is defined by the manufacturer. 

So, while the temperature coefficient generally causes an increase in Voc, at temperatures below -20°C, other factors related to extreme cold can impact the overall performance and efficiency of a PV module.

[Dominik Damberger]

Thank you for the quick reply.

However, the values from my screenshots before don't seem to match the values in the following windows, even though the same module was used:

In my original post Voc was at 49.4 V at -10 °C. In a string with 30 modules this adds up to 1482 V, which fits to the first screenshot in this post. However, at -15 °C PVsyst previously calculated a value of 49.6 V. With 30 modules in series this should of course then add up to 1488 V. Yet in this case PVsyst calculates a value of 1501 V.

Any thoughts?

[Linda Thoren]

Indeed, the second screenshot indicates a Voc(-15°C) of 50.0 V, though the Internal model result tool at TOper of -15°C results in Voc of 49.6 V.

On the "Basic data" page of the PV module's definition, the frame "Internal Model result tool" allows to display the main electrical characteristics under chosen operating conditions. This tool is only informative. It doesn't hold any parameter for the definition of the PV module.

We will investigate the reasons behind the discrepancy and apologize for the inconvenience and confusion this is causing