Is your feature request related to a problem? Please describe.
Related to #1689, it would be nice to have a linear self-shade power loss model.

Describe the solution you'd like
Once a shaded fraction is calculated, power loss can be calculated by modifying equation 6 from [1] and assuming that power loss is linear (as is done in SAM for thin film [2]).

For a linear shade loss, shade-corrected power, Psc, can be related to estimated power with no shade, Pns, with

Psc = Pns * (1 – FS * (1 – DF))

where DF is diffuse fraction (I've used a fixed value, i.e., 0.2, but it could be estimated more precisely in each timestep using satellite data, dirint or gti_dirint, etc.[3]).

This approach works well when using measured (unshaded) POA irradiance.

Describe alternatives you've considered
...

Additional context
I'm not sure where the equation for Psc came from. I first implemented it in 2021, and more recently thought that it came directly from Lorenzo 2011 [1], but now I don't think that's the case. And I think SAM simply reduces beam irradiance for the linear shade model and already has diffuse irradiance separately, so does not need to calculate a diffuse fraction.

This method does not explicitly account for reductions in diffuse irradiance due to row to row shade.

This was presented on at PVRW 2023 [4].

[1] E. Lorenzo, L Narvarte, and J Muñoz. 2011. "Tracking and back-tracking". Progress in
Photovoltaics: Research and Applications 19: 747-753. https://doi.org/10.1002/pip.1085
[2] Gilman, P. et al.., (2018) SAM Photovoltaic Model Technical Reference Update. 93 pp.; NREL/TP-6A20-67399
[3] K. Anderson, W. Hobbs. Improved CdTe PLR Estimates: Self-Shading and Spectral Mismatch. NREL PVRW, 2022. https://www.osti.gov/biblio/1846944
[4] I. Azad, W. Hobbs, "Improved PV expected energy modeling with a simple self-shading model". NREL PVRW 2023. (proceedings pending)