[Feature]: Allow integer investments without integer unit commitment #871
Description
Feature description
Currently, the only way to use discrete capacity decisions is to set the UCommit settings parameter to 1 for unit commitment with integer clustering, which also then applies integer unit decisions to capacity decisions (for thermal units only).
It would be more flexible to permit capacity decisions to be integer while keeping operational commitment decisions a linearized relaxation of the unit commitment constraint set.
It would also be even more flexible if we permitted discrete unit sizes for other resources besides thermal units, even without unit commitment.
(All of this anticipates GenX use cases with Benders decomposition which will isolate discrete build/retirement decisions from the decomponsed and parallelized operational sub-problems as well).
Motivation
There are substantially less capacity build/retirement decisions (one per cluster) than operational unit commitment decisions (one per cluster and per operational time step).
In real-world portfolio planning contexts, a user may also want to specify a specific discrete project capacity for a wind, solar, storage, hydro etc. project corresponding to a real project build/no build decision (e.g. a discrete decision about whether to build specific Windfarm A or Windfarm B?).
Implementation strategy
To permit integer build for thermal units only: create a single distinct settings for integer build decisions and integer or linearized unit commitment for thermal units.
To permit integer build for other units: add a column to the resource input csv file for each resource that can be used to specify if a specific resource cluster is to be treated as integer build decision or not.
Additional context
No response