How to POA irradiance for tilted surface

vshyam1992
Topic Author
New Member

07 Nov 2017 18:28 #5825 by vshyam1992

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

Hello Paul

Is SAM using DNI and GHI data from the weather file to calculate the POA irradiance which is " subarray 1 POA irradiance total nominal? just making sure?

Regards
Shyam

Please Log in or Create an account to join the conversation.

Paul Gilman
Platinum Member

07 Nov 2017 21:55 #5826 by Paul Gilman

Replied by Paul Gilman on topic How to POA irradiance for tilted surface

Hi Shyam,

Yes. If your system has one subarray, then the POA irradiance at the surface of the array is the value SAM reports as "Subarray 1 POA irradiance total nominal."

Best regards,
Paul.

Please Log in or Create an account to join the conversation.

vshyam1992
Topic Author
New Member

17 Nov 2017 15:37 #5827 by vshyam1992

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

HELLO PAUL,

I am using Subarray 1 POA irradiance total nominal for calculating tilted surface solar irradiance at angle- 45 and azimuth -180 degrees. I am using 1-subarray to calculate, but the results are very different from RETScreen compared SAM. I am using same parameters. I am getting a huge variation in the monthly and annual data as well. I don't know what I am doing wrong. Please suggest me

Please Log in or Create an account to join the conversation.

Paul Gilman
Platinum Member

17 Nov 2017 20:51 #5828 by Paul Gilman

Replied by Paul Gilman on topic How to POA irradiance for tilted surface

Dear Shyam,

I am not familiar with the values that RETScreen reports. Be careful with the units and make sure you are comparing equivalent values. For example are you comparing total monthly values to average daily values by month?

Also, check the azimuth angle convention: For SAM 180 degrees is due south, regardless of the hemisphere. Some models use zero degrees as due south in the Northern hemisphere and due North in the Southern hemisphere.

Best regards,
Paul.

Please Log in or Create an account to join the conversation.

vshyam1992
Topic Author
New Member

18 Nov 2017 18:34 #5829 by vshyam1992

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

HI PAUL,

In order to get the POA irradiance, do I have change any settings in Albedo- Sky Diffuse model- irradiance data( advanced). I am trying to get POA irradiance data from pyronometer and the reference cell, but I am getting an error here, It's not letting me simulate the results.

Please Log in or Create an account to join the conversation.