André Mermoud

This problem will be fixed in the next version 6.41.

When the diffuse is available on an hourly file, PVsyst will always use it. This is the case for your Meteonorm external file. If a dataset is imported from Meteonorm (internal to PVsyst), the diffuse is also calculated by Meteonorm. Now there is a mistake in the denomination in the PVsyst report: the model for diffuse used by Meteonorm is indeed the Perez model, not the Erbs model. I just got the confirmation from Jan Remund last week. We will correct that in the next version. However I don't see well how the fact to know which model is used could have so "huge" effects on the shading calculations. The effect of diffuse is more important on the transposition.

This is typically a problem of time shift between the recording time of your data and the time of PVsyst (i.e. when the solar geometry is calculated). Please see the help In V 6.40: "Meteo Database > Notes on Meteo > Meteonote9_Time shift in meteo files" In V <= 6.39: "Meteorological Data > Hourly Meteorological Data > Time shift"

Yes, the denomination of the data source "US TMY3 (or TMY2)" has been changed into "NREL National Solar Radiation Dababase" in the version 6.40. We will revert to the old denomination in the next version 6.41.

Yes your reasoning is right: the soiling loss is specified in terms of percentage of the yield. Therefore if low irradiance in winter, the loss will be lower in absolute value. For your monthly analysis you have to consider the absolute losses, not the percentages.

The cell's temperature at sun is established using a little energy balance model. The parameters of this model (U-values, possibly accoding to the wind velocity) are of your responsibility, and defined in the "Detailed Losses". The model is explained in the help "Project design > Array and System losses > Array thermal losses".

When the inverter is able to produce reactive power (i.e. able to produce a phase shift), the Nominal Power (PNom) may concern - either a limitation in Active (real) energy, expressed as [kWh] - or a limitation in Apparent energy, expressed as [kVA]. This limitation is rather usual as it is equivalent to an output current limitation. This is a a property of the inverter, therefore a choice in the definition parameters.

You have to purchase rights for updating, for one year. See our web site www.pvsyst.com, > Order.

Grid systems with battery storage are not a simple problem, and are not yet implemented in PVsyst. Please see our FAQ Can I include a battery in a grid-connected system ?

This option "Partial shadings calculation" in the menu of the 3D editor is meant for defining a partial part of your system, in order to decrease the computing time of the shading effect. When using this option, the shading factor will be computed on this sub-part of the system, and applied to the whole system. There is no option for simulating the production of a single inverter (or any part of the system). If you want to do that, you have to specify only this reduced system in your simulation.

This location which stores the basic prices for the pre-sizing is in the "Hidden parameters". These are basic values, not really meant for being modified by users. Here it is only possible to specify basic prices in Euros. Now in all places where costs are involved in the software, you can choose the currency, and specify the exchange rates as you like (the exchange rates database is not really up-to-date: please check the values when using it !). The prices in EUROs specified in the Hidden parameters will be converted in the chosen currency. NB: Please be very careful with this pre-sizing tool and the proposed prices: this is a very rough tool, just to be used for a very first evaluation of the potential of a project. More reliable results will of course be provided by the detailed simulation ("Project design"), and here, in the economic evaluation, you can specify your prices directly in your own currency.

Please have a look on our FAQ With my big power plant, the calculation time is prohibitive. In the version 6.40 the shading calculations will be faster, and the tool for calculating on a partial system will be improved.

This is indeed a limitation of PVsyst: - with the Helios3D scenes (spread of orientations due to different baseslope for each table), there is a special mechanism for the averaging of the orientations. - This averaging has not been developed for the seasonal tilt option. The average is not defined for the Winter tilt, so that the simulation cannot work correctly. We will analyze the possibility of extending this option for a next version, but it is not trivial (and marginal in PVsyst).

PVsyst uses the one-diode model. It is very difficult and hazardous to get satisfying results with such simplified models.

As explained in the warning message, you have to specify corresponding orientation parameters in the "Orientation" part and the 3D part. NB: By the way you should not define a "Horizontal E-W axis", but a "Tilted or Horizontal N/S axis.

When you create a shading scene, PVsyst checks the compatibility of your system, i.e. that your sensitive area is sufficient for positioning all the modules defined in the "System" part. You are strongly advised to follow the tutorial present in the main menu of PVsyst, just below the Help option.

The diffuse fraction is computed using a model (Liu-Jordan or Erbs, Perez-Ineichen, or others, described in the literature). The solar angles calculations are detailed in the help of PVsyst (Chapter "Physical models used"). The shading factor for beam is a calculation in 3D geometry, for a given sun's position. The shading factor on diffuse and albedo are integrals of this shading factor over the sky dome "seen" by the PV system. All these calculations are complex and cannot be obtained just from a formula.

The planned power is obviously 50 MWp. In PVsyst you can specify 2 different sub-arrays, one for eack kind of modules. You have detailed tool for the determination of the PNom ratio.

The files produced by PVsyst up to V 6.39 are written in binary format, and impossible to read by other means than PVsyst. The new version 6.40 will produce text files, easy to edit. However these text files are intended for internal use. We will not ensure any support about their interpretation.

Yes of course the simulation takes the voltages (battery and PV module) into account. The corresponding loss is named "Pmpp loss" in the loss diagram. Now a 60 cells module is really not suited for the direct charging a 24V battery bank. You should use at least 66 cells modules, the usual design is to use 72 cells. For better results, the MPPT controllers are now not much more expensive than usual switch-off controllers. And you get rid of the Module's voltage constraint.

Skelion exports models from the Sketchup representation, but the representation of objects in Sketchup is not really compatible with the way PVsyst is waiting for shading objects. You can try importing these scenes, perhaps they will look correct, but we don't guarantee the shading calculations. We will implement our own Plugin for Sketchup within the next months, with our own constraints about the structure of the object's representation.

With such an inverter, this is not advised (or not possible) due to the current limitation. However with other inverters (those with the secondary input dedicated to one only string, and when it is allowed by the manufacturer), you can indeed use only the main MPPT input. In this case you should inform PVsyst by using the "Adjust" button.

This is not possible in PVsyst. You should do different simulations with parts of your system.

I have given the answer to this question in my last post: However, since the redaction of this answer, the limits have been migrated to the Project's parameters (button "Albedo and Settings", page "Other limitations", parameter "Max. orientation difference for defining average (spread) orientation".

You have chosen an inverter with a special feature named "Unbalanced Inputs". This means that you have two different MPPT inputs (in this case, with Imax = 49.5A and 37.5 A respectivaly), named "Main" and "Secondary" inputs. With such special inverters, PVsyst requires that you define two different sub-arrays, one for each kind of input. In your case you will define the first sub-array for the main MPPT input, 3 strings and the corresponding orientation. And a second sub-array for the secondary MPPT input, 2 strings and the corresponding orientation. NB: You can add sub-arrays either by specifying the number (top left) or by right-clicking on the sub-arrays page titles. NB: The fractional and strange PNom values are due to the fact that the PNom of each input is shared as function of the Current's shares: 49.5A and 37.5 A lead to PNom = 13.7 kW and 10.3 kW.