Shading derate factors: Month by hour(version 2014.1.20)

Hi Paul,

I am working on batch processing of photovoltaics Flat PV model using SamUL. I am trying to input shading derate factors using the month by hour method as shown in the SAM help section -> SamUL Scripting Language -> Interfacing with SAM analyses. My script is running fine without errors, but I am not sure whether I am using the correct input and output variable names. Can you point me to a discussion or a link where I can find the exact name of variables to be used in SamUL to:

1) Make sure the month by hour beam irradiance shading derate method for subarray1 is enabled.

2) Input variable name to enter the shading derate factor values using month by hour method.

3) Output variable to crosscheck the correct input is being used for simulation.(Currently, the only output variable I found was system.hourly.subarray1.beam_shading_factor. But this variable seems to be giving a different value than expected)

The only variable related to shading derate I found in the Input Variables directory was: pv.subarray1.shading. Can you explain a bit about how to use this variable?

Thanks & Regards,
Hemang

Dear Hemang,

The pv.subarray1.shading variable is a one-dimensional array that contains all of the information in the shading window.

As far as I can tell:

The first element in the array should be 2.

The next four elements either enable (1) or disable (0) the shading factor tables in this order: hourly, month by hour, azimuth altitude, diffuse.

The next three elements are unused.

The next 8,760 elements are the hourly factors.

The next 288 elements are the month by hour factors.

The next two elements are the number of rows and number of columns (respectively) in the azimuth by altitude table.

The next rows x columns elements are the azimuth by altitude factors.

The last element is the diffuse factor.

This is a little easier to work with in SAM 2014.11.24 with LK script because LK can directly access the SAM simulation core (SSC) variables so you can work directly with the tables of factors.

Best regards,
Paul.

Hi Paul,

Thanks for the reply. Is it possible that you send me an example of this variable being used in a SamUL script? This sounds complex. Also, is there an output variable which can be used to check the inputs ?

When I downloaded the latest November version of SAM, I realized I cannot open the older .zsam files in the latest version. If that is possible then I can surely try using the LK.

Hemang

Dear Hemang,

Yes, that array is complicated, and unfortunately, no, I do not have an example of a SamUL script that works with it.

To check the outputs, the beam_shading_factor variable is shows the product of all shading factors that apply in a given time step. If you change the soiling factors to 1, it should show only the effect of the shading factors.

SAM 2014.11.24 cannot open .zsam files because the underlying file structure is different from SAM 2014.1.14 and older versions.

Best regards,
Paul.

Hi Paul,

Thanks for your responses earlier. I am following the above mentioned description and creating an array accordingly. I am using this array as an input to the variable "pv.subarray1.shading". The attached file shadingscene contains all the array elements. But, when I run the simulation, I am still getting an error with this message:
"error setting up ssc shading inputs for subarray 1, err=-2"

Hemang

Dear Hemang,

Would you mind sending me a copy of your .zsam file with the script? You can email it to me at sam dot support at nrel dot gov if you prefer not to attach it to your original post.

Best regards,
Paul.