André Mermoud

In PVsyst, the cables temperature is fixed to 50°C at any time, supposed to be an "average" during all conditions of the simulation In the reality, the wire temperature is obviously not well defined: it depends on the wire mounting mode, the possible exposition to the sun, the current, etc... The sensitivity of the resistivity to the temperature is 0.39%/°C, for the copper as well as for the aluminium. See the help https://www.pvsyst.com/help/project-design/array-and-system-losses/ohmic-losses/metal-resistivity.html?h=resistivity NB1: in a next version, it will be possible to choose the temperature for any part of the wiring. In the present time, you can modify it in the advanced parameters. NB2: the wires temperature has nothing to do with the cell's temperature in the module.

This parameter "Maximum current per MPPT" is indeed quite correlated to the "Minimum voltage for attaining PNom". See the help https://www.pvsyst.com/help/component-database/grid-inverters/grid-inverters-main-interface/grid-inverters-main-parameters/index.html#input-side-dc-pv-array Now if this is specified, PVsyst will apply this cutrremt limit during the simulation. But this rarely produces "Inverter losses due to current overload", as this limit is most of the time preceded (masked) by the Power overload limit. See the Help https://www.pvsyst.com/help/physical-models-used/grid-inverter/inverter-operating-limits.html If the limit is not specified, it is obviously not applied. Now this limit is not always well "understood" by the manufacturers who submit their data, nor well defined in the datasheets. Sometimes we have to add this information afterwards in the database.

PVsyst is a software for the study of PV systems. It is meant for the storage of PV energy, not the grid energy. It is not a suited for the simulation of any BESS systems on the grid.

What dou you mean by "Types of cables" ? The different types of cable (of a same metal) have in principle the same resistivity, and this is the parameter which determines the power loss. If you are talking about the installation mode: - The resistivity may indeed depend on the cable temperature, and therefore on the installation mode. - The main thing to be considered will be the current limit for a given cross section, which is specified in norms.

In the DC circuit (array of strings), the total wire length is indeed the lenght of the whole loop (this si mentioned just below "Please specify the total wire length for each circuit. " For the AC circuit, this is the line length (distance between devices).

Probably you have defined your transformer by a generic relative loss, i.e. proportional to the transformer nominal power. And this nominal power - evaluated by PVsyst on the basis of the PNomPV at STC, or the PNomac (this is your choice in the Project's settings) - has been changed in your different runs. This should not arise if you define an explicit transformer from the datasheets, the nominal power of the transformer will always remain the manufacturer's value. In this case the "generic" relative values will be updated as a function of this real Transformer nominal power.

There may be new features in the version 8, which were not implemented in the version 7. Now for the modification of the Rshunt and Rserie values, this was a feature of the software which has been mpdified. In the version 7, when they were judged not quite correct, these values were updated to default ones. This is no more the case in the version 8.

The files created in the V8 cannot be used with the version 7.

You can add a battery in your database from scratch by using "Databases => Batteries => New". But you are strongly advised to choose a similar battery in the database, modify its parameters according to your own component datasheets, and save this as a new battery. For defining an hybrid system, you should choose the button "Storage" in the project's dialog, and probably choose the option "Self consumption" for your case.

No, in the present time PVsyst doesn't consider the charging of the battery from the grid.

Sorry, it is completely impossible that PVsyst changes these parameters by itself. Please carefully check that you are comparing the same variants. NB: You can always reload and install the old version 8.0.13 if necessary. Both versions may be used simultaneously.

This is quite normal as you have defined a grid limitation of 1 kW (for a system of 200 kWp, 180 kWac). You can notice that the apparent value is 79 kVah, to be compared to a global delivery to the user of 224 MWh, i.e. 0.04%. Please note that you have the opportunity of completely forbid the injection to the grid when you define the self-consumption:

Yes indeed, the battery model of PVsyst uses information which is not always present on the datasheets. Some datasheets are really very brief. When you have to define a battery by yourself, you are advised to start from an existing battery, and adjust the relevant variables (mainly technology, kind of battery, number of cells in series and parallel, internal resistance (check dafault), self-discharge (check default), lifetime (numbe of cycles), sizes and weight

You can find some data about the current and voltage degradation in the works, namely, of the TISO in Switzerland. For example in this publication: https://www.researchgate.net/publication/256080133_TISO_10_kW_30_years_experience_with_a_PV_plant

We obviously don't avail of detailed ageing data for a specified PV module. The average degradation rate itself is really not well defined. In the literature you can find a wide panel of values (0.3% to 1%/year). The PVsyst proposition of 0.4% seems a reasonable choice for usual modules. The specific mismatch effect due to ageing has been developed "theoretically" as a tool in PVsyst, without any experimental basis. We don't know any publication studying this problem in the literature. The hypotheses under this evaluation (Monte Carlo evaluation of the dispersion progress) are purely speculative. Therefore this model is obviously not able to take your particularity into account in a reliable way. You can probably take a lower value for the Isc/Vos RMS.