SAM Open Source Older Versions

Hello, 

For a research project, I built the open source version of SAM from the current patch branch. I am trying to recreate results obtained using an older version. To this end, I meant to select a specific PV module (Jynco JKM265PP) and a specific inverter (Fronius SYMO 17.5-3-M). Those specific items are not available in the current version, so I selected JKM265PP-60 and Fronius SYMO 17.5-3-M respectively.

To make sure the discrepancy in my results upon recreating the model are not (only) related to this change in components, I thought I would also build the relevant older version of SAM ( github.com/NREL/ssc/tree/2017.1.17/ ). However, I cannot find the build instructions for the old version.

So my first question is whether the old components can be loaded somehow into the new build, and the second would be where can I find the instructions pertaining to the old version? 

Best regards, 
Lina

Hi Lina,

If you just need access to the old module library, the easiest may be to download the appropriate legacy version of SAM from sam.nrel.gov/download , install it, and find the library CSV file in the libraries folder of the installation.

The link you shared is to the SSC repository, which does not include files for the SAM user interface, including module and inverter library files. The SAM releases don't go as far back as SAM 2017.1.17, but you can download a .zip archive of the source code for  2020.2.29 r2 and later that includes the library files from github.com/NREL/SAM/releases .

You can also find historical module and inverter library data here: github.com/NREL/SAM/tree/develop/samples/CEC%20Module%20and%20Inverter%20Libraries .

Best regards,
Paul.

Hi Paul, 

Thank you for your answer. The library files were helpful in isolating the factors leading to the discrepancy. 

I have a follow-up, more general question regarding differences between versions. I went through the SAM Release Notes  to try to better understand the results I'm getting, but I would like a higher level of detail, if possible. Was there any modification to the calculation model/energy balance between versions 2017.1.17 and 2022.11.21 that would explain a higher yield in the 2022 version for the exact same inputs? Between 2019.11.11 and 2022.11.21?

("Fix issue when using GHI and DHI or POA options for irradiance data from weather file." from the release notes could be relevant as we do use GHI and DHI option). 


Additional details:
{To recap and clarify, I built the open source version of SAM from the current patch branch (so version 2022.11.21). A colleague had built the open source versions of SAM consistent with 2017.1.17 and 2019.11.11 for an earlier iteration of our project. In all builds, the open source version was modified identically, allowing the additional input of roof surface temperature and using it instead of the ambient temperature to estimate the back of the panel temperature. Data from different roofing configurations (e.g. white roofs, green roofs, black roofs) is used and compared to investigate the effect of this roof choice on the PV yield. Consequently, as expected, a white roof configuration, for instance, leads to a higher yield. The current issue is that the results obtained with previous modifications (2017 and 2019) report a higher percentage difference between white roofs and black roofs, for example. So basically, the sensitivity of the yield to the back of the panel temperature seems to have decreased. I would like to know what changes have been implemented to the energy balance or yield calculation (perhaps transmission efficiencies?) so that this is explainable. Note that I have also tried running the official SAM versions for the same inputs (2017 and 2022) and the 2021 version had a higher yield even without any modification from our side.}


Thank you for your valuable input.

All the best, 
Lina

Hi Lina,

You might try looking at the code history on GitHub to see what changes might be causing the differences you note. For example, changes to cmod_pvsamv1.com are listed here: github.com/NREL/ssc/commits/develop/ssc/cmod_pvsamv1.cpp

There is additional code in the ssc/shared folder, for example lib_cec6par.com: github.com/NREL/ssc/commits/develop/shared/lib_cec6par.cpp

I will try to look at this more as well, but wanted to point you to those resources in the meantime.

Best regards,
Paul.