André Mermoud

This is a generic error. We cannot say anything with just this information. When occuring, you are asked for sending us a bug report. This helps us a lot. Otherwise, please send us the screenshot of your error message (full screen), with a complete description of your problem (what you are doing, etc). Send it to support@pvsyst.com.

Applying the probabilistic evaluation P90 to hourly, daily of even monthly values doesn't make sense. P90 is an annual evaluation. Please see our FAQ "What is the P50-P90 probability production ?". PVsyst only allows mixing the orientation #1 and #2 on a same inverter input. This is a limitation. Now you can define several sub-arrays, with different MPPT inputs, for different orientations. The sub-array - i.e. inverter MPPT input - may only be defined in an homogeneous way (same module, same number of modules in series).

The Minimum voltage for getting Pnom is equivalent to an input current limitation. By defining VminPNom, the minimum voltage for attaining PNom, we have: - Imax = Pnom (DC) / VminPNom, - where Pnom(DC) = PnomAC / Efficiency. If this value is specified in the inverter, it is obviously taken into account in the simulation. Everything is explained in detail in the contextual Help "Physical models used > Grid inverter > Inverter Operating Limits" and other topics.

The relevant parameter is "Limit overload loss for design" in the Prject's definition (button "Project's Settings"). See the FAQ Can I define a system with highly undersized inverter ?

Since V 6.68, there is a new loss named "Global incident below threshold" in the loss diagram. For simulation hours when the GlobInc value is below a given threshold, PVsyst doesn't perform the full simulation: this is considered as a "not significant" hour. This threshold is fixed at 10 W/m2. Remember that by very covered weather conditions, you have still 40 to 50 W/m2 ! Up to now this (little) loss was included in the Near Shading or IAM loss contribution. For balance coherency, this is now accounted independently. This contribution rarely overcomes 0.05% in yearly values.

The procedure is fully described in the help "Project design > Bifacial Systems", and "Project design > Bifacial Systems > Bifacial system: 2-dimensional unlimited sheds/trackers".

No, you cannot do that.

The P50 - P90 concept is explained in the help "Project design > P50 - P90 evaluations" It is a probabilistic interpretation of your simulation result. It is only applicable to an annual result. You can connect at most 2 orientations on an inverter input. Please define these 2 orientartions, and you can choose (Mixed orientations 1 + 2) in the sub-array. NB: All module of each string should be in the same orientation. You cannot mix orientations within a string.

This is explained in the help "Component Database > Pump definition". However this is a complex topic: if you have detailed datasheets, you can ask me for including them in the database.

No sorry, the PDF provided by PVsyst are now closed for avoiding manipulations of results.

This depends on how you define a Micro or a String inverter. To my opinion, a micro inverter is suited for one module, i.e. with a Pnom of less than, say, 300 W. In the present time, by "String inverter", people usually talk of inverters suited for 2-4 strings, i.e. some few kW. More than 15 years ago, some inverter manufacturers called "String inverters" devices for which all the safety components (usually present in the roof junction box) are included in the inverter. This is the definition of PVsyst.

By definition, the "Array virtual energy at MPP" is the value at MPP. It is obviously not modified by this condition. This loss will be accounted in the inverter losses "under the voltage threshold".

The “Ground reflection on front side” is a by-product of the Bi-facial model. It is not possible to calculate it with "normal" systems, without several additional parameters and a calculation model that we don't have at disposal at the moment (the bi-facial model is specific for unlimited sheds). By the way its value is very low for usual tilts. To my knowing, this quantity is never calculated (nor taken into account) by any other PV system simulation tool.

PVsyst will report Errors (in red) which prevent the simulation, and "Warnings" (in orange) which indicate a not optimal choice, but allow the simulation. Now when PVsyst reports an error (for example in a component), it is not able to get results, or the results may be erroneous.

Please see our FAQ How to adapt PVsyst to floating systems ?

Perhaps it will useful to read the help "Project design > Bifacial Systems". Everything is explaned in detail here. Namely the View factor gain (geometric calculation) should be thought as an Energy transfer. When passing to irradiances, it should be renormalized with 1/GCR.

This is not yet implemented. Please see the FAQ How are managed the new "twin-modules" with half cells.

For the sizing of cables in the DC part (PV sub-array), you have a tool in "Detailed losses > Ohmin losses > detailed computations". In this tool, you can open "Wires" for the main properties of each cable section. Please also see the help "Project design > Array and system losses > Array ohmic wiring loss".

You have obviously some limitations in voltage and power when using an inverter. And also some reasonable conditions. Your array of one string of 8 modules represents 1.16 kWp. This is obviously not suited for an inverter of 4.6 kW. PVsyst puts some reasonable limits. Now when increasing the number of modules is series, you overcome the voltage limit. You should put several strings in parallel instead.

This depends on the Manufacturer's conditions of course. To my opinion, if the inverter is correctly designed, there is no reason for limiting the nominal power of the connected PV array, because the power limitation is ensured by the inverter itself, by displacing the operating point on the I/V curve. Now if this condition is marked as contractual in the datasheets, you have to observe it of course. You have a checkbox in the PVsyst definition of the inverter, indicating whether the condition is contractual or not. If checked, PVsyst will not allow to design a system overcoming this condition.

Sorry, this error message is erroneous. Probably your import has not been successful, the MET file doesn't hold any data, and result in this error message. We have worked a lot for improving this importing tool in the next version 6.71. In order to help us understanding this problem, please send us your source file, the *.SIT file used for the import, and your *.MEF formatting file. Send them to support@pvsyst.com.

GlobInc is the irradiance on the plane, calculated by the transposition model. GlobEff is the irradiance effectively falling on the PV modules, after optical losses like shadings, IAM or Soiling. You should compare with GlobInc of course.

Probably your Meteo file is not complete. The optimization of the transposition factor can only be performed on a complete year of data. Now be aware: there is a bug in the version 6.70: the transposition factors plot (optimization) crashes. You should revert to a previous version for getting this plot, sorry.

You can get a lot of solar geometry results, for any location, in "Tools > Tables/Graphs of solar parameters".

We don't know this problem, we have never observed such a strange behavior. The problems with CSV files produced by PVsyst are usually due to bad settings in your EXCEL (decimal character, separator, date format, see "Internationalization" in EXCEL and Windows). This case seems really strange. Please send us your full project, using "Files > Export projects" in the main menu. Address it to support@pvsyst.com.