kjs55
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Posts posted by kjs55
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Hello,
Every large-scale project in the USA is commissioned with an ASTM E2848 capacity test. The derived Measured Power is compared to the derived Modeled Power. Global plane-of-array POA irradiance Gpoa is essential to this multiple linear regression-based test. Measured Gpoa needs to be comparable to Modeled Gpoa (apples-to-apples).
Measured Gpoa (front-side facing):
- Sometimes installed entirely unshaded
- Sometimes installed on the (vertical) bottom of the frontmost array
- Sometimes installed on the (vertical) bottom of an array shaded by the row in front
- Sometimes installed on the (vertical) top of the frontmost array
- Sometimes installed on the (vertical) top of an array shaded by the row in front
- Sometimes installed in the (vertical) middle of the frontmost array
- Sometimes installed in the (vertical) middle of an array shaded by the row in front
- Sometimes installed on the (horizontal) edge of the frontmost array
- Sometimes installed on the (horizontal) edge of an array shaded by the row in front
- Sometimes installed in the (horizontal) middle of the frontmost array
- Sometimes installed in the (horizontal) middle of an array shaded by the row in front
- Sometimes installed at a fixed tilt
- Sometimes installed on a tracker (tracking)
- Sometimes measured with pyranometer(s)
- Sometimes measured with reference cell(s)
Measured Global POA (rear-side facing):
- Same options as above except rear-side facing
- Replace "frontmost" with "rearmost"
What is the comparable Modeled Gpoa to use for each of the above scenarios? For example, for rear-side Gpoa that is entirely unshaded, do we have to run a separate simulation w/ the structural shading loss factor removed?
My suggestion is this: Allow us to simulate the measured front- and rear-side global POA effective and incident irradiances at specific (user-specified) point locations in the array for the purposes of running the capacity test. Report it as separate columns of PVsyst other than the typical GlobEff, GlobInc, & GlobBak (e.g., Geff_SimMes, Ginc_SimMes, Geff_SimMesBak, & Ginc_SimMesBak). Other options than "_SimMes": _MesPt, _PtMes, _Sensor, etc.
Finally, sometimes one or more pyranometer(s) is used for measurements; other times, one or more reference cell(s) is used. So, I think it’s important to simulate both front- and rear-side global POA effective and incident irradiances, respectively, at the given user-specified (front- & rear-side facing) locations in the array.
Thanks.
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Upon reducing Grid AC Power Limitation applied at POI (-9.27%), these changed by the following relative amounts:
BkVFLss: -0.01%
IL_Oper: -0.1%
IL_Pmax: -0.01%
EArray: -1.11%
Plus changes to several losses after the inverter. Would you please comment on EArray? Thanks again.
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Thanks for your quick reply.
1. Unfortunately, I cannot share the models, b/c the project details are proprietary.
2. I'm curious if the four model outputs I listed are expected to change (in theory) as a result of the one (single) changed model input that I described.
3. If I have time (no guarantee), I'll see if I can reproduce it using the PVsyst Demo bifacial model. In the meantime, please feel free to do the same exercise, especially if the answer to #2 is "No". -
PVsyst v7.2.11: The *only* change between the two (bifacial) models is a reduced Grid Power Limitation at the point of interconnection POI (grid injection point). Nothing else changed in the models (carefully confirmed).
Differences in losses before the inverter:
1. Observed in exported numeric loss tree:
- View Factor for rear side (BkVFLss) loss
- Inverter Loss during operation (efficiency) (IL_Oper)
- Inverter Loss over nominal inv. power (IL_Pmax)
2. Observed in PDF output report table named "Balances and main results":
- Effective energy at the output of the array (EArray)
Also, several losses after the inverter (before the grid injection point) changed, which I won't list here unless someone requests it. Thanks.
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Just a quick note/small point to say that the number of significant figures for wind speed in the PVsyst 8760 output .csv file is more than expected, e.g.:
WindVel, m/s, 0.6, 0.2999, 0.2001, 0.5, 0.5, 0.8999, 0.5, 1.5999, 0.8999, etc.
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Hi, It looks like the option to apply a grid power limitation at the inverter level vs. injection point is an EITHER/OR. But, what if we have limits at both the inverter level AND the injection point? It doesn't look like we have the option to apply losses at both points (nodes) in the system (it's only EITHER/OR, not AND). I suggest adding the AND option. Thanks.
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Finally, here's the error message that occurs when trying to edit a post after about 1-min. following submission: "This comment can no longer be edited. It may have been moved or deleted, or too much time may have passed since it was posted for it to be edited."
Essentially, I'm proposing to please remove the time limit for editing posts, similar to the previous PVsyst Forum setup. Thanks.
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This is post is just a test (to try to generate & transcribe the "option to edit has timed out" error message).
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P.S. Interestingly, I saw the "Edit" option appear in the ellipsis of my above reply for a brief time following my submission of the reply post. However, that option quickly disappeared after about a minute or so, and now only the options "Report" and "Share" remain in the ellipsis of the reply post (similar to the original post above). Again, I think it'd be very valuable if we can edit our posts over the long term (to add further context & details as we think of it, etc.)!
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Thanks so much for your timely & thorough reply - it's very much appreciated. I tried clicking on the ellipsis, however, all I see (as a normal, non-admin user) are the following options: Report and Share. This is why I originally reached out: because I'd expected to see another option for "Edit". Thanks again.
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Hi, The previous PVsyst Forum allowed us to edit our posts after submission (for increased clarity, to fix spelling typos, to improve grammar, etc.). Can we do this on the new PVsyst Forum and, if so, how? Thanks. P.S. The previous PVsyst Forum also allowed us to preview our posts prior to submission (to view renderings of special formatting, etc.). Can we do this on the new PVsyst Forum and, if so, how?
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Hi, If possible, I'd like the ability to run simulations with monthly AC grid power limitation values (user inputs) instead of one single annual user input value. Thanks.
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PVsyst v7.2.10: Many PVsyst users and other PV stakeholders see the bifacial insolation gain in bold font in the PVsyst Sankey diagram and think this is the bifacial gain BG. However, this is incorrect & arguably misleading. A better (DC) estimate of BG is to multiply this insolation gain by the PV module's nominal (or nameplate) bifaciality factor. So, perhaps PVsyst can show this adjusted value on the Sankey diagram and put it in bold font instead. This suggestion is compliments of T. Townsend. Of course, this is still only an estimate of BG, as the true BG comes from running the simulation twice - once for bifacial and once for monofacial (i.e., bifaciality turned off - effectively a bifaciality factor of 0%) - and dividing the energy output metric of interest (e.g., AC energy injected into the grid, E_Grid) of the former simulation by that of the latter. The main suggestion here is to reduce the common misinterpretation of BG that exists due to the design & formatting of the present PVsyst Sankey diagram. Thanks!
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PVsyst v7.2.10: How do I assign a particular sub-array shading scene to a particular sub-array that has a particular orientation (azimuth & tilt - fixed or tracking)? Thanks!
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PVsyst v7.2.10: Why do I need to close the web browser (e.g., Moxilla Firefox) to install PVsyst?
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PVsyst v7.2.8:
Open SFI (.SFI file) template window in PVsyst GUI (i.e., "Output File" definition window).
Change units of power from kW to W.
OK.
Reopen.
Units are reverted back to kW.
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See subject line. Inactivity time period is only 30-min or so. What's the purpose of this? Why can't the user stay logged into the PVsyst Forum indefinitely?
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I'm running v7.2.8. I've updated my post to be more specific (v7.2 -> v7.2.8).
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PVsyst v7.2.8: Result Variable Template RVT (.rvt) files are not documented in the Help Menu.
Navigation: Technical aspects > File organisation > User data > Workspace
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PVsyst v7.2.8.
Open existing project w/ variants.
Rename project.
Save.
Prompt pop-up -> Change filename -> Save.
Do you want to copy all the Variants of the project?
Yes.
Variants are not copied.
e.g., Try it on the demo file: _DEMO_UTILITY_MAROC
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Hi, Would you please confirm the minimum diode saturation current at reference conditions I0Ref is 0.01 pA and not 0.01 nA or 0.001 nA? I only ask because it appears the minimum value of I0Ref displayed in the PVsyst .PAN file graphical user interface GUI is 0.010 nA. (I may have seen a lower value of 0.008 nA for CdTe.) Is it the same PVsyst-imposed limit for all PV cell technologies? Thank you.
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Hi,
I'm looking at the 24 pages of unanswered PVsyst Forum topics submitted by PVsyst's paying ($$) customers & users as of 2021-04-15.
It'd be neat if:
1. We (PVsyst users--perhaps specifically those w/ user accounts on the forum) could somehow upvote topics on the PVsyst Forum*, &
2. PVsyst clearly designates ticket status as Open, Resolved, or ultimately Closed (e.g., w/ labels aka tags).
*e.g., To show importance & help w/ prioritization (somehow need to limit repeat voting; perhaps tied to PVsyst Forum account? e.g., one vote per account per topic, so we can cast our votes while logged in...dunno)
Another option is to add work status tags: Approved, In Progress, Rejected, To-do, Under Review, etc.
I did a quick Google Search &, e.g., this list of status terms came up for Jira:
Thanks.
P.S. Updated "Issues" -> "Topics" as it looks like the PVsyst Forum uses the term "topics".
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Hi,
Someone recently pointed out to me that there's a mismatch between the equation for shunt resistance (Rsh) in the PVsyst help menu linked in Ref. [1] and Eqs. [5]-[6] of the paper in Ref. [2] (incidentally, also Eqs. [6]-[7] of the more recent paper in Ref. [3]; the latter paper incorporates the temperature-(not just irradiance)-dependence of PV module performance into the PVsyst one-diode model). Firstly, Eq. [6] of Ref. [2] is not in the PVsyst Help Docs in Ref. [1] at all. Reportedly (according to Ref. [10] within the paper in Ref. [2]), Eq. [6] in Ref. [2] came from a personal/private communication with the paper's author. Secondly, the term Rsh_base is replaced by Rsh_ref in the PVsyst help documents. It would be good if the PV community can reference the PVsyst help menu in Ref. [1] instead of the papers in Refs. [2]-[3] when it comes to applying the PVsyst one-diode model. For example, the Photovoltaic Performance Modeling Collaborative (PVPMC) community's website (Ref. [4]) and the associated, relevant PVLIB Toolbox function (Refs. [5]-[6]) could then reference the PVsyst Help Docs in Ref. [1] instead of the paper in Ref. [3]. If possible, please advise, and, if necessary, please update the PVsyst help menu in Ref. [1] in order to clarify this point. Thanks.
References:
[1] https://www.pvsyst.com/help/. Then navigate to "Physical models used" > "PV Module - Standard one-diode-model" > "Rshunt exponential behavior vs irradiance".
[2] K. J. Sauer and T. Roessler, “Systematic approaches to ensure correct representation of measured multi-irradiance module performance in PV system energy production forecasting software programs,” IEEE J. Photovoltaics, vol. 3, no. 1, pp. 422-428, Jan. 2013.
[3] K. J. Sauer, T. Roessler, and C. W. Hansen, “Modeling the irradiance and temperature dependence of photovoltaic modules in PVsyst,” IEEE J. Photovoltaics, vol. 5, no. 1, pp. 152-158, Jan. 2015.
[5] https://pvlib-python.readthedocs.io/en/stable/generated/pvlib.pvsystem.calcparams_pvsyst.html
[6] https://pvlib-python.readthedocs.io/en/stable/_modules/pvlib/pvsystem.html#calcparams_pvsyst/
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Hi, I don't have data to upload now (I can provide as needed), however, the new IAM models available in PVsyst based on Fresnel Equations and Snell's Law are much more accurate for real-world PV modules than the ASHRAE model. I suggest leaving the ASHRAE IAM model in PVsyst for posterity (& important comparisons) & labeling it as "deprecated" (so it's available but users are no longer inclined to use it). On a related note, I also suggest changing the default IAM profile in PVsyst to the custom IAM profile for "normal" glass (again, based on Fresnels Equations & Snell's Law). (NB: I'm on v6.8.8.) If a module manufacturer opts to apply an anti-reflective coating ARC to a given module type & they wish to represent it in the PVsyst .PAN file, they can update it to the "AR coating" setting to "reflect" that (pun intended) and achieve the associated gains over whatever timescale is expected for the given O&M processes (e.g., module cleaning), specific weather events, soiling compositions (e.g., organics build-up), and general weathering (wear-and-tear of all the elements--full spectra of light incl. UV, humidity, mechanical loads, temperatures, &c.). Thanks.
Editing and Previewing Our Own Posts on the New PVsyst Forum
in How-to
Posted
Any updates here? I just tried to edit one of my recent posts. I got an error (see below). And, for more historical posts, there's no option to Edit at all. Again, the previous PVsyst Forum more ideally allowed for continuous editing/improvements with no time constraints.
Oops!