Parametric analysis - dual tilt and self shading

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SolH
Parametric analysis - dual tilt and self shading

With regards to parametric analysis in SAM, I think the way SAM is handling dual tilt system (East-West) may not be reflective of how they are done in the real world. I create two subarrays with one facing east (90 degrees) and the other facing west (270 degrees) and split the strings between the two. I believe self shading enabled would give an inaccurate result in this case since the modules would not be racked in a sawtooth-like fashion as would be a typical east-west install.
Is there anyway to create this type of configuration under SAM?

Also, with regards to parametric analysis, there is no direct output that indicates total installed land area, I think?

Thanks,
Sol

Paul Gilman

Dear Sol,

SAM models self shading of rows of modules within each subarray. As you suggest, it assumes that each subarray is physically separated, so it cannot model shading of modules in one subarray by modules in another.

You could use the 3D shade calculator to draw the array, and then have it calculate the shading losses to apply to both subarrays.

As for the parametric runs, the land area is an input and does not get reported as an output. Here is a link to an LK script that does the same parametric analysis as you set up, but also reports the land area. Because of the large number of variables, it takes about 15 minutes to run. To use the script, download it, open your .sam file, and choose "Open script" from the File menu, and click Run in the script editor.

parametric.lk

Best regards,
Paul.

SolH

Hi Paul,

I'm trying to model a large interleaved east-west PV array with over 50 strings facing east interleaved with over 50 strings facing west. I would like to take into account self-shading. As you say SAM cannot "model shading of modules in one subarray by modules in another". Your suggestion of using the 3D shade scene calculator is a good one. However, it seems the 3D scene calculator is intended for small arrays and not large ones. Any suggestions how I can make this work?

Thanks,
Sol

Paul Gilman

Hi Sol,

It is true that the 3D shade calculator was originally designed to model small rooftop arrays, but it can be used in some cases for larger applications. I would recommend experimenting with it to see how it works. Because the model calculates a percentage reduction in beam and diffuse irradiance, you might not need to draw the entire array. Instead, you might be able to represent your array by drawing a section of it to calculate self-shading percentages that apply to the entire array.

Best regards,
Paul.

SolH

Can the 3D shading scene be read from an LK script?
I've tried the following 3D shading scene to a large east-west system but it did not seem to make any difference.

Paul Gilman

Hello,

When you use the Shade Calculator to generate shade data from the scene you draw, SAM stores the data in the subarray[n]_shading variable, where n is the subarray number. From an LK script in SAM, you can read the the shading data, but not the scene itself.

The Shade Calculator has a separate LK script environment where you can draw the scene using a script. To use that feature, open the Shade Calculator and click Scripting. We've posted an example of an LK script for the Shade Calculator in the LK Cookbook here https://sam.nrel.gov/samples.

I'd be happy to look at your file if you want to email it to me. If you do, please include both a .sam file and .s3d file. (Export the .s3d file from the Shade Calculator window.)

Best regards,
Paul.

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