André Mermoud

As you mention, when tilting the base of a table its orientation changes. See our FAQ With sheds on a tilted roof, PVsyst changes my orientations With the Helios3D scenes, PVsyst performs an average of all table orientations. You can get detailed information about this distribution and the averages in the 3D editor, menu "View" / "Orientation analysis (Hekios3D)". You will have the list of all tables and their orientations, different distribution plots, and the average calculation.

Let's consider row arrangement (sheds) systems only. In this case when one row puts its shade on the next one, the bottom cell row is primarily shaded. Let's call submodule the set of cells protected by one by-pass diode. In most modules (60 or 72 cells), there are 3 by-pass diodes and therefore 3 "sub-modules", usually disposed in length within the module. Let's suppose that the modules are disposed in landscape, and all modules of the bottom row belong to the same string. Now it is often believed that when the bottom cell row is shaded, the by-pass diodes will limit the electrical loss to the sub-module row, i.e. the string electrical production will remain 2/3 of the normal production. This is only true (about) if you have one only string per MPPT (violet curve). If you have more than 2 strings in parallel, the electrical shading factor is shown on the next figure: this shows that as soon as 1/3 of the sub-modules are affected by the shade, the electrical loss is 100%! Electrical shading factor according to the number of shaded submodules in a string (this plot may be constructed point by point using "Tools" /"Electrical behaviour of PV arrays") Therefore in rows arrangements, the protection diode don't recover any electrical loss: the full string width (module with) should be considered as electrically inactive as soon as the bottom cell is shaded. With the calculation "according to string" in the 3D model, this means that with row systems the Fraction for electrical loss should always be set to 100%. With "Unlimited sheds", the width of the full string should be considered. The next figures show how the I/V curves are affected: the first shows a not-shaded string One only string without shadings and when 1/3 of sub-modules are shaded: we loose in voltage, but the current remains the same. If the string is alone in the array, the Pmpp loss is proportionnal to the number of shaded sub-modules. One string with 1/3 submodules shaded Now when there are other strings in parallel, the MPP is chosen on the resultant I/V curve, and the voltage Vmpp is the same for all strings: for the shaded string, only the diffuse contributes ! 1/3 shaded string in a 3-strings array

In the "Module Layout" calculation, PVsyst always takes the best MPP point indeed. I don't see how to do differently: how to decide which maximum is really taken by the inverter ? By the way this represents a very low energy uncertainty: - the shading situations with 2 MPPt are not very significant: they only concerns the situation when the diffuse component is higher than the beam component, due to particular shading dispositions. - for usual systems, the full electrical shadings loss (module layout calculation) is less than a very few percents during the year. The additional loss would be a fraction of this loss. - the power difference between both points is not necessarily very high.

Yes of course. In this case you define different sub-arrays, one for each array kind.

This has been corrected in the version 6.20.

I don't know any well-established consensus for the simulation of the degradation of a PV system. The usual way is to take the module efficiency degradation into account. Manufacturer's warranty usually corresponds to about -1%/year, but the very few experimental studies about this subject indicate a lower degradation rate (around -0.3%/year on 25-years installations at Supsi - Switzerland). Usually the yield diminution is assumed to be directly in accordance with this degradation. But a recent study pointed out the fact that all modules don't degrade identically, but with a spread around the average, so that the mismatch also increases along the years. In PVsyst, we intend to provide a tool for the estimation of this phenomenon soon. The performances of other parts of the equipment (like inverters) probably don't degrade significantly, but may be subject to failures. The "instantaneous" loss may be accounted by the "Unavailability" during the simulation, and provision for the repair or replacement should be included the maintenance costs.

Yes, in the present time PVsyst is not able to import POA values measured with a tracking sensor. And I don't see any possibility to do this "manually": the transposition factor depends on the GlobHor, but also on the DiffHor irradiance values. When importing POA data, PVsyst performs an adjustment for retrieving a set of (GlobHor, DiffHor) values, which will exactly represent your POA data when transposed to the tilted plane (with the Hay model). We intend to extend the importing tool for tracking systems in the future. But sorry, I don't know when we will have time to do that. This requires that in the importing format, all Tracking parameters (including mode ans stroke limoits) should be carefully defined.

Each Power optimizer works on a different mode, so that it needs a specific development in PVsyst. I have worked closely with Solaredge for elaborating the SolarEdge architecture. I'm on the way just now to develop other power optimizers, with the help of their manufacturers. The TIGO technology should be available soon (within 1-2 months).

In the present version, the electrical shading effect is supposed to be null (or negligible) with the SolarEdge architecture. This is one of the main advantages of the SolarEdge technology, due to the fact that all modules operate with a common current within a string, and all strings operate at fixed voltage. Therefore I don't think I will extend the Module Layout possibilities to the SolarEdge system: I would not know how to do that. However I'm working on other power optimizers, and there may be some residual electrical shading effects, that I'm just investigating now. The results of these studies will be published with a future version of PVsyst, within hopefully 2-3 months.

Don't try to find an explanation. This is indeed a bug. I big bug, that I have never seen. Please check the Efficiency curve in your Inverter's definitions. However this should not arise of course. Please send me your whole project, using "Files" / "Export projects" in the main menu. (andre.mermoud@pvsyst.com)

The OK button stays grey until you have entered full valid data for defining your site (i.e. at least valid Global horizontal and temperatures monthly values). This prevent defining erroneous sites in the database. Now you can define these values either by importing them, or by hand (you can also paste them from EXCEL). The dialog should tell you what is incorrect. Now the sites for the US are stored partially under "USA" and partially under "United states" according to the country definition which have been made in each SIT file.

You can get the old installation packages of PVsyst V6 at the following address (you should adjust the 6_1_9 to your desired version): http://download.pvsyst.com/index.php?page=download&prod=true&key=PVsyst-prod%2Fbin%2FPVsyst6_1_9_setup.msi

This is not the right place for performing PVsyst simulations. You should use (on the main page) : "Project design" / "Grid connected". Here you are in a special (advanced) tool for the analysis of data measured on a PV system. DAM files are meteo files including additional measured data about your system (for example output energy).

This is not the right place for performing PVsyst simulations. You should use (on the main page) : "Project design" / "Grid connected". Here you are in a special tool for the analysis of data measured on a PV system.

These are quite different calculations. The "Unlimited sheds" option uses a simple analytic shading factor calculation, which supposes that the sheds are very wide (neglects the edge effects). The 3D shadings are based on the full 3D geometry calculation, but can use (according to your choice) a pre-calculated shading factor table, which may induce interpolation uncertainties. Both use also an integral for the diffuse and the albedo, which also depend on these calculation modes. The difference between both calculatioons is 0.4% in your case, which may be considered as acceptable. We usually observe a little bit lower difference, but please check that you did use the exact similar geometry (i.e same "inactive bands" for example).

Yes it is still difficult. I have established a model (i.e identified 3 main modifications of the standard one-diode model) which works quite well, and matches the real modules behaviour with a very good accuracy. The problem when using this model in PVsyst is to find the good parameters, as the information provided by the manufacturers is usually not sufficient. However the default parameters proposed by PVsyst seem to give good results. See my paper Performance Assessment of a simulation model for PV modulesof any available rechnology, ( 25th EPVSEC – Valencia, 2010), available on our site http://www.pvsyst.com.

In the version 5.73, the night losses are the iron loss of the external inverter. In this version, night loss of the inverter output or auxiliary losses had not been implemented yet.

For the PAN "proprietary" format: if you want to reproduce the old DELPHI encoding of reals on 6 bytes, and modify/update your reading according to all specific parameters defined (or not) for each PV module, I can give you the format. You will probably spend several days (or weeks) for using it. I really don't know any model specifying the effects of the humidity on PV modules, and I can't imagine which phenomenons could affect the PV module behaviour (except morning condensing effects). Please explain. However the meteo data of PVsyst don't include the Humidity information in the present time, and I don't intend to include it unless very strong reasons. Now for the comment of the W7 cell, you should indeed read: "For crystalline modules: if not specified, will be a result of the one-diode model, which is very close to the usual reality".

For the shading loss changes: If your system involves unlimited sheds: in the version 6.13 to 6.18, there were an error when reading the VCi file. The plane tilt used for the evaluation of the shading effect on the diffuse part was not read correctly, which underestimated the shading loss. This error didn't occur with new calculation versions, or if you opened the "Orientation" dialog before the simulation. This problem has been corrected in the version 6.19. On the other hand, the diffuse model is the same in both cases: just the denomination on the report has been changed. "Measured" was used previously for any values read on an hourly file (whatever the origin, which is not known by PVsyst). Now for most meteo data, the diffuse is indeed issued from a model. Therefore this denomination is not correct. In the new versions we have tried to put some more accurate description when we have an idea of the origin of the data. When creating synthetic data (which uses the Meteonorm algorithm), the diffuse is constructed by the Meteonorm software, using a Liu-Jordan or similar (Erbs) model.

The PAN files are written in a specific binary format, only readable/writable by PVsyst. If you want to manage PAN files explicitely, you can use the Import/Export facility to an EXCEL document. You have a template of this EXCEL document in your \PVsyst6_Data\UserData\. The Import/Export procedure is explained in this document. However it is of course not possible to add your own parameters in the file, besides the "official" format. How would they be recognized by PVsyst ???

If so, this is indeed a bug, and I will investigate this. However in the "Detailed Losses" part, if you define the IAM explicitely by unclicking "Uses definitions of the PV modules", the IAM is now specified for the sub-array itself, and will be kept if you change the PV module.

The 6.1.9 version is indeed the 6.19. I don't know why you cannot install it. Please explain what happens.

Each array connected to a given MPPT input should be "homogeneous" (i.e. identical PV module and number of modules in series). You should define one sub-array for each kind of "homogeneous" array.

Yes, if there are several inverters, the section managed by PVsyst is indeed the sum of all individual sections of all inverters. The minimum section proposed by the program corresponds to the section allowed (by usual practice or regulations) for the concerned current.

I don't know. Which version are you using ? Please send me you full project, using "Files" / "Export whole projects" inthe main menu (mail to andre.mermoud@pvsyst.com).