About PARTITION (and its effects on the strings) and FRACTION FOR ELECTRICAL EFFECT

[C. Amorevole]

Hello PVsyst forum,

After readings the suggestion (the "?" icon) where it talks about the little tables systems, I had a question about the partition's effects: 

Generally (since I use string composed by 30 panels and my trackers are composed by 30 panels too or 15), according to what suggestions in the image above suggest, it seemed convenient to me to place the little tables close to each other. So "all the bottoms will be shaded at the same time, and the rest of the table will become inactive, in the same way as for a big table". What does this last sentence mean? To become inactive means that there is no contribution on energy production by the totally or partially shaded tables/strings? what does PVSyst calculate on the string if only part of it (for instance only a single table of 15 modules of the 2 (2x15=30 modules=1 string) that combine the string) is shaded and the rest is totally radiated? Does it involve also the fraction for the electrical effect? If yes, how does it work?

thank you

[Michele Oliosi]

Hi the help page will be updated after our upcoming patch 7.3.3. Hopefully it will make things more clear.

The basic idea is that any partition that is partially shaded will contribute as if it was completely shaded. That's what is meant in the text when saying "become inactive".
There is no notion of "shaded string" when using the partition model, only of shaded partition.

If you have only half the modules in the string that have the same shading, the resulting electrical shading loss is difficult to model with the partition model. There are two cases:

• the string is on a single table in a 2x15 configuration. This is in general fairly well modelizable with the partition model. Depending on the type of module (half-cut cells or not) and its orientation (landscape or portrait) you may need to put a different number of partitions to model this properly. 
• the string is on two tables in a 2x(1x15) configuration. In this case, there is not much you can do with the partition model to model this accurately. In general however, this situation is marginal on your whole system, so it is okay to assume that in "most cases" the shading is the same for the two trackers.