Hi Paul,
Thanks for the quick response. When I turn off the snow loss model, I don't have the issue anymore, which is expected because the solution path to convergence changes.
I re-did my process, printing out the "snow" and "dcsnowderate" fields in addition. I see the same behavior shown in the linked Github issue: dcsnowderate is one of [0, 0.5, 1], and a value of 0 results in no generation. For the hours in question, dcsnowmoderate = 0.5 in one iteration and 0 in the other, so that is indeed the cause!
After reading up on the snow loss model in
this NREL article
, my theory is that the slight decrease in irradiance is enough to shift the "snow sliding" inequality (T_a > I_poa / m) from True to False in some hours, which I believe means that snow is still left on the panel, and the output is 0.
With that said, I have two follow-up questions:
- Now that the issue has been resolved in development, could you provide any estimate on when/how the patched snow loss model will become available to users?
- Even after the fix is applied, would you expect that this discrete generation jump that I described (depending on whether the snow sliding inequality is satisfied) will still be occur, either to the same or lesser degree?
Thanks again,
Ian