gallery example for bifacial modeling with pvfactors

[spaneja]

• [ ] Closes #xxxx
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• [ ] Tests added
• [ ] Updates entries to docs/sphinx/source/api.rst for API changes.
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• [ ] New code is fully documented. Includes numpydoc compliant docstrings, examples, and comments where necessary.
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The gallery does not currently have any examples for bifacial modeling. After looking into the issue, it appears that it is somewhat clunky to perform bifacial modeling with the modelchain. As such, I have created two examples of bifacial modeling, with the pvfactors approach, and would like the community to weigh in. One example uses the modelchain, while another is procedural. I will wait for feedback on which approach is more suited for the gallery.

At this time, much of the documentation inside the examples is not complete or is copy/pasted from another example. I will clean and polish this when a decision is made on modeling approach.

[kandersolar]

Thanks @spaneja! I agree it makes sense to decide what we want the examples to do before getting into the nitty gritty about code formatting and such.

First though, the docs build is failing because ReadTheDocs doesn't currently install pvfactors before trying to run the examples. Can you update this PR and add a 'pvfactors' entry to this list in setup.py? https://github.com/pvlib/pvlib-python/blob/master/setup.py#L59-L62

[cwhanse]

Thanks @spaneja. I would vote to move forward.

Generally, I think the ModelChain approach is about as clean as pvlib v0.9.0 can support. This is an important example to add, which may also help us see how to deliver bifacial capabilities through ModelChain methods.

The procedural approach looks OK to me also, with the exception of the list structure for irrad; maybe that's a pvfactors issue but references like irrad[0] are rather opaque.

Ping me when you want to start working on commenting, etc.

[spaneja]

Thanks @cwhanse and @kanderso-nrel. I have gone ahead and cleaned up and edited the submissions here. Please take a look for your approval and let me know of any feedback that you have.

[kandersolar]

Thanks @spaneja, here are some notes.

[kandersolar]

It's a small inelegance that specifying aoi_model is necessary for a ModelChain that only uses run_model_from_effective_irradiance. I don't see a way around it, so I don't think there's anything to be done in this PR, just thinking out loud about the ModelChain design.

[cwhanse]

Could default to None but then we'd need to check for a valid model in other run_model methods.

[cwhanse]

Converted to #1411

[kandersolar]

Referring to #1398, we should think about the choice of n_pvrows in these two examples. I think it would be a good idea to explicitly specify n_pvrows=something (so that at least the choice is explicit in the code instead of implicit via the default value) and leave a comment briefly explaining why the user may want to choose a different value.

[campanelli-sunpower]

PSA: I have a "pre-release" of pvfactors v1.5.2 up at https://github.com/SunPower/pvfactors/releases/tag/v1.5.2. All that this left is to name it and for me to get cred's to upload to PyPI, see SunPower/pvfactors#137.

[cwhanse]

Thanks @spaneja

[cwhanse]

Converted to #1411

[kandersolar]

Thanks @spaneja!