Time series fuel costs

[samgdotson]

This PR adds a new rule to the workflow that accesses time series cost data from the PUDL project. Merging this PR closes #29 and closes #30.

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How the data is processed

1. The cost data are downloaded and come in $/MMBTU on a monthly basis.
2. The data are multiplied by the appropriate heat rates to get fuel costs in $/MWh
3. NaN values are removed by linear interpolation.
4. The data are resampled to the appropriate hourly scale using a forward-fill strategy.
5. Lastly, in the add_electricity rule, the VOM costs are added to each timestep.

[pep8speaks]

Hello @samgdotson! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file scripts/retrieve_costs.py:

Line 7:1: E402 module level import not at top of file

Comment last updated at 2024-09-03 14:10:30 UTC

[samgdotson]

Hello @samgdotson! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file scripts/retrieve_costs.py:

Line 7:1: E402 module level import not at top of file

Comment last updated at 2024-09-03 14:10:30 UTC

I'm ignoring this PEP8 issue because the preceding line sys.path.append("functions") is necessary to import the module in question. Perfect adherence to the style guide, here, would break functionality.

[ssattler]

This looks fine - I had my comments in the earlier pull request,
-Sandra

[samgdotson]

Thanks @ssattler! If you're satisfied with these changes, would you mind clicking the big green "Merge pull request button?"

This PR needs to be merged before #36.