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PostPosted: Tue Jul 31, 2012 3:34 pm 
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Joined: Mon Apr 16, 2012 7:29 pm
Posts: 1662
This is not a problem of computer performances.

3D shadings calculation
In the 3D tool of old versions, the calculation of the shading factor went with the square of the number of elements; the elaboration time of the shading factor table becomes prohibitive above some few tausends of elements.
In the version 6, this calculation has been optimized, with a gain of up to a factor of 10 in speed. For using this feature, make sure that in the menu of the 3D editor, the option "Tools" / "Optimized shading calculation" is checked. Since then Version 6.6, this calculation uses the "OpenGL" tool, and this is no more a problem.

In your 3-D shading scene, you should not define one rectangle for each PV module. This is not the right way.
The "tables" (sheds or rectangles) of PVsyst are generic surfaces, intended for receiving a set of PV modules. You are advised to define each table as big as possible according to the constraints of your configuration. For example, when you have side-by-side sheds, you can define a big one instead.

Calculation on partial systems
NB: Since V 6.44, it is possible to specify a representative sub-part of the system (for example the input of one only inverter), and during the simulation the shading calculation will only be performed on this sub-system, but applied to the full system.
This concerns the "Linear shadings calculation", and the calculation "According to modules strings". This tool doesn't apply to the "Module layout" calculation. However this is no more really useful as the normal calculation is sufficiently fast now, event with very big systems.

Advice: with very big power plants, if the configuration is regular (i.e. with flat ground) you are advised to perform your first simulations (for optimization purpose) using the generic option "Unlimited sheds" in the "Orientation" part. In this case you don't have to define a 3D shadings scene, and the calculation will be straightforward.
This is for example useful for optimization analysis of the row-to-row distance and shed tilt

Module Layout calculation

The detailed calculation of the electrical effect according to the Module layout option is also very time-consuming, without possible optimization.
This option is not suited for very big system.
For multi-MW systems, you should evaluate the electrical shading loss with the "ModuleLayout" option using a part of the system (say - one inverter, i.e. one MW) and extend this to the whole system.
Since version 6.67, PVsyst puts a warning for systems over 1 MW, and prevents the definitions of ModuleLayout for systems bigger than 5 MW. This upper limit may be increased in the hidden parameters, topic "System design parameters, losses, shadings".

For evaluating the electrical shading loss in bigger systems, you should:
- Define a variant with a representative sub-system of your full big system (for example a sub-array connected to one central inverter, i.e. around 1 MWp).
- Define the "Module Layout" for this sub-system, and perform the simulation. You will get an electrical shading loss value.
- Recaclulate the Electrical losses with the option "According to Module strings" for this sub-system, with "Fraction for electrical effect" = 100%.
- Comparing the results for electrical loss will allow to estimate a "Fraction for electrical effect" leading to a same loss value.
- You can now define the option "According to Module strings" for the whole system, and apply this new "Fraction for electrical effect".

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