EME 810
Solar Resource Assessment and Economics

2.16 Applying Shading Factors in SAM


System Advisor Model

I hope you were successful installing SAM software and getting it ready to use in the last lesson. Now you will be applying your interpretation of the shading diagram to determine shading factors and input them into SAM for system energy performance simulations where shading interferes with the solar resource.

We have come a long way in interpreting sun path diagrams and plotting shaded areas as overlays onto the sun path charts. How can we input those shade/no-shade conditions to the PV performance model in SAM? The video below provides a demo of how shading conditions can be applied in SAM simulations. 


This video is made using the 2020 version of SAM. In newer versions, some tab specifications may differ.

Video: SAM Shading Intro (6:26)

SAM Shading Intro
Credit: M. Fedkin © Penn State University is licensed under CC BY-NC-SA 4.0
Click here for a transcript of the SAM Shading Intro video.

How do we apply shading factors in system advisory model? I'll show you just in a second. I'm using System Advisor Model SAM, version 2020, and I'm going to start a new project. Here button on top-left. And for the example of the solar array given in the lesson two assignment for EME 810, we will need to choose photovoltaic long left side menu of options for my system. But you will not need all of them for this assignment, you actually will need only a few. Location and resource where you set location for your project. Then system design where you can tweak some of the parameters of the system and obviously shading, because that's where we apply the shading factors. Okay, let's go one-by-one. Set things up for it. First.

In the assignment, it states that the system we're working with is located in Baltimore. So, we need to find that location. I have Baltimore in my weather file library if you don't see one in yours, So, you may just go down here and search by location and pull that file into a library first. So, once I click on it, I also see it appearing down here, weather data information in Baltimore, so it's good to go. The system design. We can set the parameters of the system close to what we have in the assignment. So, I can set the nominal capacity for the systems here. It's four kilowatts. So, I'll leave it at that. And also, if I scroll down, I can put the tilt 35 degrees and azimuth for the system close to the ones that are described in the textbook and described it in the assignment. So, the system is oriented nine degrees east of the two south, so that would give me 171. And that's all I need here.

Now to shading. On the shading options. The area you want to look at is this, shade loss tables. If you click on edit shading, it will give you a number of options and how you input your shading data. And the one you need is enabled month-by-hour beam irradiance shading losses. So, click here, and now it brings up this table that you can use to input your shading factors for each month of the year from January to December for each hour of the day. How to use this table. It's very easy. If you have no shade, you leave it at zero, which is default. You have full shade. You need to enter 100%. Like this. And it's, your area will be shaded. You can also apply to multiple cells, for example if, I'm sure that my area will be shaded 100 per cent, for months of January and February, I can apply that 100 shading factor for all those cells for both months. The same way, I can apply it to any other months of the year. Like October through December, for example. Once I have those factors setup, I click Okay, and I go to simulation.

The output of the model shows me the annual energy here from my system in kilowatt hours, shows the capacity factor, and monthly energy profile. You can also print this monthly data in the table. For that, you would need to go to data tables here on top. Choose monthly data. Scroll all the way down through all those many variables. You need system AC energy kilowatt hours per month. Click here. And wallah, you have January through December, your output in kilowatt hours.

If you add them all up, you should be getting that annual energy that was given in the summary here. For this assignment, you will need to model your system for both shaded and nonshaded scenarios. So obviously you can go back and modify this table. I can apply zero to all cells here, indicating no shade. This will be my baseline. Click. Okay. And I simulate again. You see the profile of the energy output changed significantly. So, your goal will be to compare those two scenarios and find out how much shading losses you would have.

So, the important take-aways are that we can use SunCharts or other geometric shading data to get us to a shade-based performance adjustment of PV performance simulations, and that shading matters in solar energy. How significant can it be? Quite significant, but you will get a more accurate answer after performing your homework assignment in this lesson! We use these SAM simulations in solar project design, and this will be the way to assess the shading losses for any specific scenario (and in your final course project, eventually). 

When working with SAM shading table, we can input partial values for hours that are on the shade/no-shade borderline (e.g. 50% etc.). SAM conveniently grades the color scheme from white (full sun) to red (full shade) in the process. Also, note that the locale matters! Do not forget to set your location in the Location and Resource tab first: the default for SAM is often in the Southwest USA, and you will need a correct solar resource file before running your simulations.