Equations For Calculating Diffuse Horizon Shading Factor

Hello again,

A couple years ago I posed a question about horizon shading to the forum:  sam.nrel.gov/forum/forum-general/2204  I received a very helpful and prompt answer from Steve, however I still have some questions about calculating the diffuse fraction. 

I went to the lines Steve referenced in his answer, but I think there must be a discrepancy between his version of the .cpp file and the one I'm seeing because the lines don't seem to contain the code Steve describes. Regardless, I don't quite have the background in C++ to fully understand the code. Particularly, I don't see how array tilt is included in the calculation of the diffuse shading factors.

Could you please provide the equations in a non C++ format one would use to calculate the diffuse shading factor, i.e, the parameter labeled  in the module of the SDKTool? 

Again, I understand conceptually that this is the ratio of the sky seen by the array (total skydome - what's obstructed by the horizon - what is not seeable because of the array's tilt) / the total area of the skydome. 

thanks for your patience,
Joe

Hi Joe,

I changed the line numbers in Steve's reply to "permalinks" to the code in s3tool.cpp on GitHub, which I hope helps you find the relevant code.

Best regards,
Paul.