Add h2 fuel cell technology

[yijinli22]

Summary

Adds h2-fuel-cell (hydrogen-powered fuel cell) as a new technology option in ReEDS, complementing the existing ng-fuel-cell (natural gas fuel cell) already in the model. Both technologies share the FUEL_CELL subset and are toggled together by the existing GSw_FuelCell switch. The H2 fuel cell uses hydrogen as fuel (h2fuel), is classified under H2_COMBUSTION, and has three cost scenarios (conservative/moderate/advanced) based on Reznicek et al.

Technical details

Implementation notes

• h2-fuel-cell follows the same tech classification pattern as ng-fuel-cell: both belong to FUEL_CELL in i_subtech.csv and are banned together when GSw_FuelCell=0
• h2-fuel-cell uses h2fuel fuel (same as H2-CT and H2-CC) and is classified as H2_COMBUSTION in tech-subset-table.csv
• Cost data loaded via plantcostprep.py by adding h2-fuelcell to the existing conv_techs loader loop, using switch plantchar_h2-fuelcell
• Unit size: 100 MW; max age: 30 years; construction time: 3 years; min load: 5%; heat rate: ~9.03 MMBtu/MWh (Reznicek et al.)
• Dollar year: 2022$, converted to 2004$ via standard deflator

Additional changes

• postprocessing/tech_aggregation.csv, tech_map.csv, tech_style.csv updated for h2-fuel-cell display (color #87A21D, aggregated as "Fuel Cell")
• cases_h2-fuelcell.csv added with 6 test runs: USA_defaults, USA_defaults_fc_adv, USA_defaults_fc_mod,USA_defaults_fc_con, USA_decarb, USA_decarb_fc_mod
• Minor syntax fix in b_inputs.gms: updated h2_combustion set comment to include fuel cells

Switches added/removed/changed

Switch	Values	Default	Description
GSw_FuelCell	0, 1	0	Existing switch — now enables both ng-fuel-cell and h2-fuel-cell
plantchar_h2-fuelcell	h2-fuelcell_conservative, h2-fuelcell_moderate, h2-fuelcell_advanced	h2-fuelcell_moderate	New — H2 fuel cell cost and performance scenario

Relevant sources or documentation

• Reznicek et al., IDES BOP Report v2 — unit size and performance parameters

Validation, testing, and comparison report(s)

TBD

Checklist for author

Details to double-check

• References for all H2 fuel cell operational data
• Charge code provided to reviewers
• Included comparison reports for appropriate test cases
• Documentation updated if necessary
• If input data added/modified:
  • Dollar year recorded and converted to 2004$ for GAMS (dollaryear.csv updated for h2-fuelcell_* scenarios, 2022$)
  • Units specified (MW capacity, $/kW capex, $/kW-yr FOM, $/MWh VOM, MMBtu/MWh heat rate)
  • Preprocessing steps documented and committed to ReEDS_Input_Processing
  • No large data files — all inputs are small CSVs
• No change to process flow (runreeds.py, solve.py)
• No change to spatial/temporal resolution

General information to guide review

• Zero impact on results of default case (GSw_FuelCell=0 by default — no change when switch is off)
• No large data file(s) added/modified
• No substantive impact on runtime
• No change to process flow
• No change to package requirements

Did you use LLM tools (chatbot or copilot) in the preparation of this PR? If so, describe how

Yes — Claude Code (Anthropic) assisted with writing the PR language

Tag points of contact

@yijinli22