kjs55

PVsyst v6.8.6. Horizontal single-axis tracker with unlimited sheds. 1.) The value entered into "Shed total width" does not save, and 2.) the "Uses backtracking" toggle checkbox Boolean does not save.

According to IEC 60904-1-2, a PV module's "bifaciality factor" aka bifaciality coefficient is the minimum of the bifaciality coefficients of Isc or Pmax (i.e., whichever is lower). The PVsyst help menu [1] says to use the bifaciality coefficient of Pmax. Please explain why PVsyst is not aligned with IEC 60904-1-2 in this regard. Thank you. [1] https://www.pvsyst.com/help/bifacial_module.htm

The crashing problem that affects PVsyst v6.7.8 was fixed in later versions. Thanks!

According to @solarguru in Ref. [1], the following post is outdated and needs to be updated: https://forum.pvsyst.com/viewtopic.php?t=40/ [1] https://forum.pvsyst.com/viewtopic.php?f=4&t=4587 @solarguru claims that Perez (not Hay) should be used Please confirm it

Nonetheless, I think it is important that users understand the impact of pitch for bifacial ## Mono-facial (v6.84) Pitch = 10.22 m; Annual Energy = 2803 kWh/yr Pitch = 100000 m; Annual Energy = 2820 kWh/yr Impact: 0.6% ## Bifacial (v6.84) Pitch = 6.6 m; Annual Energy = 4479 kWh/yr Pitch = 100000 m; Annual Energy = 12694 kWh/yr Impact: 283% (NB: The mono-facial system above is not the same as the bifacial system apart from bifaciality; so, please do not compare 4479 to 2803 kWh/yr, etc.; "impact" above is the annual energy deviation b/w pitch #1 and pitch #2 for either mono-facial or bifacial; "impact" can be compared across mono- vs. bi-facial)

Thanks @solarguru but the deviations I reported are larger (>10%) using Perez vs. Hay I am interested to hear PVsyst's opinion on this There are no issues reported for the imported measurement data however the PVsyst POA does not match the imported values

PVsyst v6.84: I am importing measured irradiance data from a tilted global POA pyranometer (GlobInc aka GPI). I would expect Mod GlobInc to exactly align with the Mes GlobInc that I am importing; however, this is not the case. The first measured GlobInc value is 446.7 W/m^2. Upon importing, I look at the modeled GlobInc value at the same timestamp. GlobInc (Hay model) for the same tilt and azimuth is 416.0 W/m^2. So, there is a 7% deviation b/w Mes and Mod GlobInc at this timestamp (at times the deviations are larger than 7%). The deviations are notably larger at the edges of the day (morning/afternoon) compared to around solar noon. I have set PVsyst to use the Hay transposition model per the following post: https://forum.pvsyst.com/viewtopic.php?t=40/ Another note: For both Hay and Perez, it reports albedo = 0.2 for GlobInc; however, there is no option to define albedo when importing custom measured irradiance. Should albedo be a user input to the custom data import tool?

As of PVsyst v6.84: Summary: When you open an existing project, save as new, and try to copy all variants, the variants are not copied into the new project Steps: 1.) Launch PVsyst v6.84, 2.) Project Design\Grid-Connected, 3.) Load _DEMO_Geneva.PRJ, 4.) Replace file name, 5.) Save, 6.) Click "Yes" when PVsyst prompts user: Copy all Variants? Result: The variants are not copied.

As of PVsyst v6.84: 1. My project uses imported measured weather data via: PVsyst\Tools\Measured data analysis. When I export the project ZIP file, I get several sequential error popup messages: """ Conversion error of string "1005.076,6.012,8.885,9.95...6.5, 74, cont'd," => Real """ 2. It appears that the following important project files are not packaged in the ZIP bundle as expected: --SIT file --MEF file --DAF file

v6.83: The name of the hidden parameter has changed: Verifications on Grid systems\The Inverter power is strongly oversized

v6.83: I found the relevant hidden parameter: Verifications on Grid systems\The Inverter power is strongly oversized

v6.83: The name of the hidden parameter has changed: Verifications on Grid systems\The Inverter power is strongly oversized

PVsyst v6.83: I see a Hidden Parameter for "Maximum PnomRatio for inverter sizing" but not for "Minimum PnomRatio for inverter sizing". Is there a technical reason why the latter is missing? Is there some other way to set the latter using some other parameter(s) in PVsyst (hidden or not)?

V6.83: Many modules in the PVsyst PAN File Database have the wrong Pnom (leftmost column), e.g., for module type "TSM-295DD05A.08(II)" with file name "Trina TSM_295DD05A08_II.PAN", the Pnom listed is "255 Wp 26V" instead of "295..."

PVsyst v6.81 1. Glass refractive index (n) appears to be 1.526, not 1.53 as shown in Hidden Parameters. 2. It does not appear that n=1.37 for EVA (in Hidden Parameters) is used for "Normal glass" or "AR coating" scenarios. 3. With the following assumptions, I get the same (tab-separated) results as PVsyst: --No ARC --Glass n=1.526 --No refractive index applied for EVA AOI IAM_PVsyst IAM_kjs55 0 1.000 1.000 30 0.998 0.998 50 0.981 0.981 60 0.948 0.948 70 0.862 0.862 75 0.776 0.776 80 0.636 0.636 85 0.403 0.402 90 0.000 0.000 4. With the following assumptions, I get slightly different (tab-separated) results than PVsyst: --ARC n=1.29 --Glass n=1.526 --No refractive index applied for EVA AOI IAM_PVsyst IAM_kjs55 0 1.000 1.000 30 0.999 0.999 50 0.987 0.987 60 0.962 0.961 70 0.892 0.889 75 0.816 0.811 80 0.681 0.674 85 0.440 0.433 90 0.000 0.000

PVsyst v6.8.1: Nothing is copied to the clipboard when you select "Export\Copy values to clipboard". To see this, go to: Tools\Measured data analysis\Detailed results\Predef. graphs\Measured values = f(simul.)\Graph\Export\Copy values to clipboard

Measured data analysis in PVsyst v6.8.1: 1.) I am wondering why we need to make a set of MEF and MET files if we have already made a set of DAF and DAM files which contain the necessary weather data; the need for both sets seems redundant -- unless I am doing something wrong? 2.) It would be nice if you could open and explore the chosen measured data file using a file open button next to the "Measured data" dropdown menu within the "Measured data analysis" tool, similar to the ability to open and explore the MET file that has been chosen using the file open button to the right of the "Meteo File" dropdown menu on the same screen in the same tool. Part of the motivation for being able to open the "Measured data" file that has been selected from the dropdown menu is that the dropdown menu truncates the filename; if the filename is long, it is useful to have the ability to confirm that the right file is selected. Another option is to avoid the truncation of the filenames, perhaps by prioritizing the display of the filenames over other fields. Thanks.

PVsyst v6.8.0: PVsyst does not ask the user whether measured POA irradiance is from a reference cell or silicon photodiode or thermopile pyranometer. So how does PVsyst take into account the different incidence angle response of flat- vs. dome-shaped glass (e.g., in reverse/forward transposition calculations)?

There is a >0.25% difference in GHI when importing the same GPI data set between PVsyst versions 6.7.8 and 6.7.9. The release notes do not mention any changes to the (Hay) reverse transposition algorithm. The impact on annual energy can be >0.5%. Any ideas of what is behind this change? (NB: PVsyst refers to reverse transposition as "retro-transposition" or "inverse transposition".)

As of PVsyst 6.7.8: This applies to both fixed tilt and tracking (grid-connected projects). I set nb. sheds = 1. I would not think collector pitch and width matter in this case but perhaps they do b/c of built-in unlimited sheds modeling assumptions? When I vary pitch from 6.6 m to a large value like 100000 m, the energy of the system goes from roughly 4700 to 14000 kWh/year. For a given pitch (nb. sheds = 1), varying width changes energy. Also, you need to close and reopen the project in order for changes to nb. sheds, pitch, or width to take effect. I will update this post later w/ more information and examples when I have time.

PVsyst 6.7.8: I can import measured ASCII weather and energy data and create a project in the Measured Data Analysis Tool in PVsyst\Tools and everything will run. However, when I exit and re-open PVsyst and re-run the exact same simulation without changing anything, PVsyst crashes.

The problem started with V6.31. Here is what I did: Opened existing PAN file in PVsyst. The PAN file has a custom IAM profile. Copy values to table. Paste values into Excel and delimit based on semicolon. Copy spreadsheet row without changing anything. Open new PAN file. Paste values from table. Error occurs in PVsyst and PVsyst crashes. Some observations: Custom IAM table is completely blank and all the angle and IAM values are "0.00". Therefore, I believe the problem occurs with the custom IAM profile. I ran it without defining an IAM profile and it seems to work without crashing.

When importing a row from the PVsyst Excel PAN file database to generate a PAN file, if the field for the quadratic factor BRev is left empty, the value of BRev in the PAN file will result in 3.2 mA/V^2 regardless of the module's Isc. I do not know what this value of 3.2 represents, but I believe it should be using the default BRev parameter that is specified in the Hidden Parameters for PV Modules, as follows: Quadratic factor BRev [mA/V^2] = 1.2 * Isc, where 1.2 is the default BRev parameter listed in units of [mA/V^2]/Isc in the Hidden Parameters for PV Modules. Thus, if BRev is left empty in the Excel spreadsheet for a module that has an Isc of 8.986 A, I believe the value of BRev in the PAN file should be 1.2 * 8.986 = 10.7832 mA/V^2 after importing, not 3.2 mA/V^2.

I am reporting a Pmpp temperature coefficient problem with PVsyst. In V6.26 and later, PVsyst changed the way that the temperature dependence of PV modules is being modeled. The brief release notes state that the derivative at 45 C is now taken into account in addition to the derivative at 25 C. PAN files in the V6 database will lead to different results depending on which version of PVsyst V6 is being run. Namely, the same PAN file used in V6.25 and earlier versions will lead to different results compared to if it is used in V6.26 and later versions of PVsyst. Also, any PAN file in the database with optimized parameters for fitting the temperature dependence in V6.25 and earlier versions may no longer be optimized for V6.26 and later versions. Likewise, any PAN file that is optimized for V6.26 and later versions may not be optimized for V6.25 and earlier versions. As an example, in PVsyst V6.25 or earlier versions, a temperature coefficient of -0.42 %/C may have been chosen as the input for µPmpp to yield an effective temperature coefficient of -0.43 %/C over the full range of temperature values (e.g., 25-65 C). As of PVsyst V6.26 and later, the inputted temperature coefficient of -0.42 %/C may yield an effective temperature coefficient of -0.42 %/C over this same temperature range. To demonstrate all of this, I simulated the exact same project in Versions 6.25 and 6.26 (500 kW in Phoenix, Arizona with a 310 W multi-Si module type). The results are as follows: PVsyst V6.25 961.64 MWh/yr PV loss due to temperature: -10.0% PVsyst V6.26 963.74 MWh/yr PV loss due to temperature: -9.8% Is it acceptable for module manufacturers to manage this bug by providing two sets of optimized .PAN files for V6; namely, PAN files that are optimized for V6.25 and earlier versions and PAN files for V6.26 and later versions?

Thanks for the useful explanation. However, I am running PVsyst V6.29 and the toggle buttons still are not enabled.