Hello,
For the CSP models, look for source code in the TCS folder rather than in the SSC folder. Also, please refer to the technical manuals listed on the SAM website for written descriptions of the models:
sam.nrel.gov/performance
When examining the source code files, it is best to do so in an integrated development environment (IDE) so you can more easily find where functions are defined. Even if you do not plan to build the project, you can download the entire repository, and use an IDE to explore the C++ code.
Best regards,
Paul.