Electrical effect when using 3D modelling

[Barbadori]

Hello,

When 3D modelling is being carried out with Helios 3D, PVCase or similar and the layout produced by that software is imported into PVsyst, do I need to apply an electrical effect factor less than 100% when choosing according to string during the simulation?

My understanding is that a 100% electrical effect is selected when shading if very regular and something between 60-80% when shading is more distributed (far buildings, trees, etc). If I choose 70% electrical effect when simulating a 3D model imported from PVCase that already takes into account topography, obstacles etc, am I overestimating losses or should I choose 100% electrical effect?

Hope that makes sense.

Many thanks in advance.

[Barbadori]

Could anyone help on this please?

Thanks.

Regards

[dtarin]

There is no straightforward answer. Are you modeling tracker or fixed tilt? What is your table size in PVsyst shade scene relative to your string length?

[Barbadori]

There is no straightforward answer. Are you modeling tracker or fixed tilt? What is your table size in PVsyst shade scene relative to your string length?

 

I'm modelling fixed tilt. I usually use tables of 4 panels on landscape and the length of the tables are 20, 10 and 5 panels, which I define on PVCase and I import into PVsyst. The actual number of modules per string is around 27.

Hope that helps.

[dtarin]

So this is the limitation in PVsyst in that we define tables smaller than our actual string size*. Before taking into account electrical effect percentages in PVsyst, the electrical effect loss is already underestimated when table sizes are smaller than the string size. A 70% electrical effect will not overestimate losses, it would be the opposite: 100% results in higher electrical effect losses compared to 70%. But since the partition size is less than the string size, that is a separate factor contributing to underestimation. This is more severely impacted with you have high undulations or tree shading.

If you have significant undulations in your terrain, or significant tree shading, you will underestimate your electrical effect losses with a 70% setting in combination with a partition size less than your string size. This also depends on your stringing configuration & the type of module (half cell or full cell). So if you're conservative in your partition definition, perhaps you can go with something less than 100%. If you're aggressive in your partition definition, then you'll be underestimating electrical effect losses if you combine that with a lower electrical effect percentage. In your case, a table length of 20 will allow you to get closer to actual shading losses. Your 4x5 & 4x10 tables may need a different partition size to avoid underestimation if your shading is irregular and significant.

*I've suggested to PVsyst they should allow for the option to exceed 100% electrical effect loss, because when we have smaller table definitions (relative to string size), we have little to no means of compensating for the underestimation of losses even when setting to 100% electrical effect. That is until the module layout method is actually useable for larger systems, or something else is implemented.

[Barbadori]

Many thanks for the answer!