DC module deviation from STC

karthik
Topic Author

21 May 2020 07:55 #8221 by karthik

DC module deviation from STC was created by karthik

Hello,
I have an issue.
After simulating a model PV system in SAM, Under the losses, I am getting a huge percentage of loss under the category "DC module deviation from STC". The Loss is 51%. I do not understand how to minimize the loss or even why it's getting so high.

My Inputs are:
Photovoltaic (Detailed PV model) - Distributed Commercial Owner.
Location: phoenix_az_33.450495_-111.983688_psmv3_60_tmy
Module: CEC performance model with module database: Canadian solar Inc. CS6U-300P
Inverter: CEC database - Schneider Electric Solar Inverters USA - Inc : GT100-480 [480V]
System Design:
Inverter -1
Module array - 12 X 28
Tilt -20
Azimuth - 180
GCR - 0.943

Shading: Self-shading (non-linear) Module orientation: portrait (1 X 12); Module aspect ratio : 1.61
Losses: soiling =0 and the rest default

Can you please help me with the issue?

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Paul Gilman

21 May 2020 17:11 #8222 by Paul Gilman

Replied by Paul Gilman on topic DC module deviation from STC

Dear Karthik,

There is a bug in the reporting of the module loss category in SAM 2020.2.29 r1 that will be fixed in SAM 2020.2.29 r2.

This issue only affects the reporting of losses, not the electrical output values.

We are finalizing that update now and hope to release it in the next few days.

Best regards,
Paul.

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karthik
Topic Author

22 May 2020 04:18 #8227 by karthik

Replied by karthik on topic DC module deviation from STC

Dear Paul,

Thanks for the information. But the output Annual energy depends on the module loss.
According to the loss diagram, my Annual energy is decreased considerably due to the module loss (more than 50%).
So, is the Annual energy is also affected because of the bug?
Can you clarify this?

Thanks,
Karthik.

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Paul Gilman

22 May 2020 22:25 #8228 by Paul Gilman

Replied by Paul Gilman on topic DC module deviation from STC

Hi Karthik,

The values shown in the loss diagram are calculated in a separate process from the energy output calculations, so the hourly output and accumulated monthly and annual output is not affected by the problem with the module loss calculation.

Best regards,
Paul.

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karthik
Topic Author

29 May 2020 13:29 #8251 by karthik

Replied by karthik on topic DC module deviation from STC

Hallo,

Today I have tried with new version SAM 2020.2.29 r2. But I am still getting 51% module loss and annual energy 97.9 MWh.
I tried the same system in other softwares such as PVSyst and PV*SOL there I am getting annual energy 128 and 129 MWh respectively.

Can you help me with this?

Thanks & Regards,
Karthik.

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Paul Gilman

29 May 2020 21:51 #8254 by Paul Gilman

Replied by Paul Gilman on topic DC module deviation from STC

Hi Karthik,

A GCR of 0.943 means that the modules are very close together. For the Standard (non-linear) self shading option, SAM includes the shading loss in the "Module deviation from STC" loss category. You could reduce this loss by decreasing the GCR, or reducing the tilt angle.

Please see the documents on the PV Validation page for comparisons between SAM, PVsyst and PV*SOL:

sam.nrel.gov/photovoltaic/pv-validation.html

Best regards,
Paul.

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