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System Advisor Model (SAM)

How to POA irradiance for tilted surface

vshyam1992
Topic Author

01 Nov 2017 14:29 #5819 by vshyam1992

How to POA irradiance for tilted surface was created by vshyam1992

Hi

I am working on a masters thesis, In here I used TMY2 and TMY3 format to get the hourly GHI irradiance(W/m2).I am trying to find the hourly POA irradiance(W/m2) from whether a file, its showing "NAh". Can you please help what am I doing wrong in here. Is there any way to find the hourly POA irradiance?
Please suggest me

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pgilman

01 Nov 2017 16:07 #5820 by pgilman

Replied by pgilman on topic How to POA irradiance for tilted surface

Hello,

SAM's photovoltaic models report the POA irradiance for each subarray. For a system with one subarray, the variable for the solar irradiance incident on the top of the module surface is "Subarray 1 POA total irradiance nominal."

The "Irradiance POA from weather file" variable is for a weather file that includes POA data. SAM can run simulations using POA data measured in the field at the array. If your weather file does not contain POA data, SAM displays "NaN" for "not a number" for that variable's value.

Best regards,
Paul.

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vshyam1992
Topic Author

01 Nov 2017 22:33 #5821 by vshyam1992

Replied by vshyam1992 on topic How to POA irradiance for tilted surface

Hello Paul,

Do you have any tutorial how to get the POA whether data (W/m2)? I want the hourly data of solar irradiation for the tilted surface in W/m2. Is it "subarray 1 POA total irradiance nominal data "

Thank you in advance,
Shyam Busineni

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pgilman

02 Nov 2017 17:22 #5822 by pgilman

Replied by pgilman on topic How to POA irradiance for tilted surface

Dear Shyam,

Yes, that is correct. You can export that data from the Data Tables tab on the Results page.

Best regards,
Paul.

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vshyam1992
Topic Author

06 Nov 2017 00:23 #5823 by vshyam1992

Replied by vshyam1992 on topic How to POA irradiance for tilted surface

Hello Paul,

I am working on the comparison between SAM and RETScreen software. In this, I am trying to find Solar irradiance for the tilted surface on PV module for both software. In RETScreen, I have monthly solar irradiance for the tilted surface in KW/m2/d (very straightforward results). In SAM, I used hourly "subarray 1 POA total irradiance nominal" and then converted to monthly (Kw/m2/d). In this analysis, there is a huge variation in the results. IN SAM, it is showing total annual irradiance as 4.0kw/m2/d and in RETScreen, its showing annual irradiance as 2.84KW/m2/d.

I am not sure where I am making mistake, am I making mistake in inputting data in SAM. But, I watched webinars for inputting data. Is there any problem with TMY3 weather file? or Do I have to use any DHI, DNI data to convert in POA irradiance?
Can you please help this analysis, I can attach the attachment if it is needed

Thanks in advance
Shyam

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pgilman

07 Nov 2017 16:33 #5824 by pgilman

Replied by pgilman on topic How to POA irradiance for tilted surface

Dear Shyam,

SAM can read weather files in the TMY3 format. Are you using the same weather file for both models? Also, please check that the tracking, tilt, and azimuth inputs are the same in both models.

SAM reports the monthly "POA irradiance total nominal (kWh/mo)" that may help you confirm that your calculation is correct. You can find that on the Data Tables tab on the Results page.

By default, SAM uses the DNI and GHI data from the weather file to calculate the POA irradiance.

Best regards,
Paul.

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