André Mermoud

If SolarGIS uses the Perez model, it should have the same accuracy as PVsyst id the input data (Ghi and Dhi) are the same. Now you should be aware that the transposition model highly depends on the diffuse component. I don't know what is the diffuse model used by SolarGIS, but if you want to do a close comparison you should use the same input data (Ghi and Dhi) in hourly values. In PVsyst, the horizon shading is taken into account before applying the transposition. Then the GlobInc (POA) is evaluated without any other perturbations. The 3D irradiance models (shadings, IAM, etc) are applied on the GlobInc, DiffInc and AlbInc issued from the transposition.

This tool in PVsyst is indeed a new feature, which tries to guess the cell sizes from available information like Sizes of the module, possible standard sizes of the cells, submodule partition, number of cells in series, etc. Now your module is not quite standard. It has 4 cells in the width, therefore 2 x submodules. Therefore the number of diodes should be 2. The configuration should be "In length" if you have indeed 72 cells in series (Vmpp around 40V), or "Twin Half-cut cells" if this has 2 x 36 cells (Vmpp around 20V) However this rather special configuration is not well treated in the present time. We will improve this in a next version.

Please explain in detail what you name "E-Battery service". In PVsyst, you can define a "Universal" battery with any specified voltage and capacity. This will have a "reasonable" average behaviour. I don't see why you are minimizing the losses. These are the reality of a system. Now when using a battery in a PV system, this is usually for charge/discharge cycles of the order of one or very few days. Therefore on a yearly simulation, the initial state doesn't have a significant influence. However you can specify the initial charge state in the advanced parameters, topic "Batteries", item "Initial SOC for the simulation".

Yes sorry. Yes, sorry. There is indeed an important bug in the version 7.3.1. When using the irradiance optimization option for trackers, the phi angles are not calculated correctly. A workaround is to revert to the usual “astronomic” calculation, which will probably be more compatible with your actual control system on the field. In the “Orientation” dialog, you should uncheck the option: This usually gives a difference inferior to 1% This issue has been fixed and the correction will be made available in the version 7.3.2.

I don't know. We have never been contacted about this error. Please send us (support@pvsyst.com) the whole project, using "Files > Export projects" in th main menu, and explain the exact way of getting this problem.

There are several ways of defining rates. PVsyst doesn't display all of them explicitly. On the loss diagram (or main results table), you have the basic results: - E_User = total user's needs - E_Solar = energy provided to the user from Solar - E_Grid = energy rinjected in the grid. PVsyst define the "Solar Fraction" = E_Solar / E_User. This corresponds probably to your "Self-production" rate.

During the simulation, there are two steps: - Define the array (cell) temperature during the simulation, according to the external conditions (Ambient temperature and Irradiance, possibly wind velocity) - Use this temperature as input for the one-diode model. For the temperature of the array, there is a model described in the help "Project design > Array and system losses > Array Thermal losses". This is based on a parameter U (heat loss coefficient) or Uc ans Uv when wind velocity is involved. For the one diode model, increasing the cell temperature will diminish the voltage and the power (about -0.35%/°C for crystalline modules).

The ohmic fraction is defined as a percentage of a "Reference Power". Here the reference power is the STC power, but it could be any other power (the ohmic fraction will be proportional to this reference power). However this Ohmic loss specified as a percentage is not the basic data. The basic data is the resistance of the wires, derived from this Loss fraction. The resistance is the same whatever the reference power chosen. This is fully explained in the Help "Project design > Array and system losses > AC ohmic loss from inverter to injection point".

The grid limitation is meant for big systems. Defining a value less than 1 kW doesn't make sense in practice. For the unavailability of the "Simulation" button when the message sais "Ready for simulation", it is indeed not normal. However this only arises when you define a grid limitation, and the Grid limit power is set to 0. We will correct this in a next version.

These values in the hidden parameters ("Low/High Grid Power limitation Power Ratio") are only used for the verification of your definitions (warning messages). The PNom ratio mentioned on the dialog is the ratio of your grid limitation specification, and the PV installed power. It is shown just for information.

The C1, C2, C05 values are battery definition parameters. These have nothing to do with the results you are waiting for. Here you have defined a charging power of 6.25 MW, for a battery pack of 27 MWh. This will indeed fill the batterty pack in about 4 hours if the PV system provides a sufficient Power for that. Which will probably be the case rather early in the morning, since your PV systerm has a nominal power of 52 MWp, i.e. almost 8 times the charging power !

The C10 is the basic definition of a battery in PVsyst. This reference cannot be changed. You can have the correspondance with other Cxx values in the battery definition dialog: here a battery defined with a C2 capacity of 105 Ah will have an effective C10 capacity of 108.4 Ah. This is the value defining this battery within PVsyst. Now when using it, the simulation will permanently re-evaluate the capacity as a function of the Charging/Discharging rate along the simulation.

The irradiance on the tilted plane is computed using the transposition model (Hay or Perez), as described in the help. This strongly depends on the beam component (i.e. the diffuse). Now when the GlobHor is modified, usually the diffuse is also affected (a higher GlobHor means a higher beam, therefore o lower diffuse fraction). This will affect the ration GlobInc/GlobHor.

The shadings calculation "According to strings" is applied to an array connected to one MPPT. With optimizers, the MPPT input is one (or possibly 2) modules. Therefore each rectangle should represent the set of modules connected to one optimizer. NB: The ModuleLayout option is also useable for the calculation of the electrical shading loss with optimizers.

There is no way in the present time for explicitly defining the tracker's position. Providing such a possibility (i.e. defining the tracker's position by an external file) is on our roadmap, but will not be realized before several months.

The simulation works exacly in this way: the individual inverter limitations are applied first. And if the grid limit imposes an additional restriction, it will be accounted as "Unused loss" in the loss diagram (provided that you have specified "Accounted as separated loss" in the grid limiting dialog). If you uncheck "Accounted as separated loss", all the losses will be accounted as inverter losses.

Yes, these are two different bugs. We will correct this for a next version, but I don't know when. NB: There is indeed no way of modifying the number of cycles within PVsyst in th present time. The only possibility is to directly edit the *.BTR file, for example in Notepad, and modify the parameters at the end of the file:

Yes indeed. providing an hourly definition of the Grid limitation is on our roadmap. However I don't know when we will be able to develop this feature.

This doesn't make much sense. The voltage mentioned here is a limit for operating conditions. The current is roughly proportional to the irradiance. The input current limit has not a "universal" definition, especially at the array level. It is not always well defined in the OND files.

As it is implicitly involved in the post of DTarin, in the present time the AC losses (Line + transformers) don't take the impedance into account; the calculation is purely resistive. Implementing the lines impedances is on our roadmap, but we don't know when we will do that.

The difference is 0.0013 %. Is it really significant ? This is a rounding effect when reading the file.

I don't know. To our knowing, the "Peak shaving" feature works quite well. Please send your whole project to support@PVsyst.com, using "Files > Export projects" in the main menu, in order that we can analyse your problem.

The Perez model calculation has not been changed. It is well-known that the Perez model has a higher gain that the Hay model. For fixed planes the difference may be of the order of 1%, depending on the tilt of course. Here you have probably a tracking system, perhaps with backtracking. This difference of 1.6% seems indeed high, but is probably reasonable. Please check that all other parameters of your simulation are quite identical.

Basically, in the present time, PVsyst works in hourly steps. Therefore this is not possible. By the way, providing 10 min output data would require to avail of 10-minutes meteo data (irradiance and temperature).

The classes are indeed of 50 kW (this is mentioned on the axis ... since the version 7.2.18! ). Now I don't have any explanation to this variability, this is a statistical variability.