Create per-plant fuel summary for FERC

The FERC fuel and steam plants table are intimately related. Without the plants table, the fuel table is... just not that useful. Additionally, some of the columns in the fuel table are junk -- e.g. the reported fuel units, or the per-unit net generation values (heat rate, fuel cost per kWh) are not meaningful unless applied to the sum of all fuels. Thus, it's possible and helpful to create a simplified summary of the core data in the fuel table for use directly with the plants table.

The fundamental information of interest that comes from the fuel_ferc1 table is:

fuel costs
fuel quantity in terms of heat content
number of units of fuel consumed

From those quantities we can also derive:

fuel cost per unit
fuel cost per mmBTU
fuel heat content per unit

However, in practice, the units field is a mess. For the most part we are usually discarding the "units" string and assuming standard units based on the different fuel types (tons for coal, mcf for gas, barrels for petroleum) and "correcting" the other quantities based on those assumptions (which isn't always correct).

Having fuel information merged in with the plants table would also provide some very valuable features for inferring which records belong to the same plant (see issue #144) and differentiating between different sub-plant level generation units, since gas and coal units are often reported as separate "plants" to FERC.

It is also very helpful to be able to filter plants based on the primary fuel type of a plant, and having the relative quantities of each fuel available in the plants table would make assigning that "primary" fuel type (or the lack thereof) very easy.

Having the primary fuel types for each plant should also allow us to fill in missing fuel type values sometimes. See #101.

catalyst-cooperative / pudl

Create per-plant fuel summary for FERC #251