Example of Shading Module implementation

Is there an example of how to implement the shading module in PySAM.default('FlatPlatePVResidential')?  (e.g. what does it expect for input)

Hi Dan,

There are a few different representations of shading in SAM. For example, for PV, there's self-shading with its various flavors, and beam shading factors that can be imported or calculated by the Shade Calculator.

Can you tell me more what you are trying to model in PySAM?

In general, a good way to get things set up in PySAM is to create a case in SAM with the inputs as you would like them, and then use the code generator (click Generate code from the case menu, by clicking the carrot "v" on the case tab) to export the inputs as "PySAM JSON" as described here: nrel-pysam.readthedocs.io/en/main/inputs-from-sam.html .

Best regards,
Paul.

I am modeling solar systems on rooftops (so self shading isn't an issue) where shading comes from objects like trees, adjacent houses and rooftop obstructions (like HVAC units).  From your explanation above, I understand that I will have to first create a shading scenario in SAM, export it and then see how to replicate that output in python to implement a shading module in code.

It looks like only shading loss parameters are available, but I don't know how to predict them.  Is there a way to correlate % shade (which I can calculate and correlates to a fraction of irradiance arriving at the plate) to shading losses?  I ran some preliminary tests and it seems like 20% shade (20% less irradiance arriving at the plate) produces something like a 50% shading loss. 

Also, where can I find a definition for constant sky diffuse shading loss?  The SAM help says it reduces the diffuse irradiance but does removing diffuse component of irradiance correlate to typical shade losses (like from a tree)?  Is it used more to model cloud cover or pollution?  I tried using it like the other parameters but found that  100% sky diffuse shading loss seems to correlate to 60% typical shading losses (and a 25%  reduction in irradiance). 

Finally, does assigning multiple shading parameters double up calculated shade values (e.g. constant 50% shading_timestep and constant 50% shading_mxh result in losses 2X that of just assigning one of the parameters)?  

Hi Dan,

One way to calculate an estimate of the beam shading factor is based on the size of the shadow compared to the size of the array. If the shadow size is 10% of the array size in a given time step, you could set the beam shading factor to 10% for that time step.

If you use both shading_timestep and shading_mxh, the result will be based on both values.

SAM applies the constant diffuse shading loss to the diffuse plane-of-array irradiance in each times step. It is intended to represent the reduction in the sky dome "visible" to the PV array caused by shading objects, and assumed to be isotropic across the sky dome and constant over time.

Best regards,
Paul.