Add h2 fuel cell technology to ReEDS main

[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. The H2 fuel cell consumes hydrogen (h2fuel, the same fuel as H2-CT/H2-CC), is gated by a new dedicated switch GSw_H2FuelCell, and offers three cost scenarios (conservative/moderate/advanced) based on Reznicek et al. (2026).

Technical details

Implementation notes

• New tech subset: h2-fuel-cell is added to a new H2_FUEL_CELL subset in i_subtech.csv and flagged under both H2_COMBUSTION and H2_FUEL_CELL in tech-subset-table.csv. It is not merged into ng-fuel-cell's FUEL_CELL subset — the two fuel cells are toggled separately.
• GAMS gating (b_inputs.gms): adds a new h2_fuel_cell(i) set; the ng-fuel-cell ban was refactored from a subset ban to an explicit ban('ng-fuel-cell') (under the existing Sw_FuelCell=0 block, behavior preserved), and a new block bans h2-fuel-cell when Sw_H2FuelCell=0. The h2_combustion set comment was updated to include fuel cells.
• Fuel & classification: h2-fuel-cell uses h2fuel (fuel2tech.csv), is added to i.csv and techs_default.csv (region type p).
• Cost data loaded via plantcostprep.py by adding h2fuelcell to the existing conv_techs loader loop, using switch plantchar_h2fuelcell. Dollar year 2022$ (dollaryear.csv), converted to 2004$ via the standard deflator.
• Key parameters: unit size 100 MW; lifetime (max age) 40 years; financing/eval period 30 years (same as Gas-CT); construction time 3 years; min load 1% ; heat rate 8.461 MMBtu/MWh ; VOM 1.7054 $/MWh; FOM ~27 $/kW-yr (moderate, 2030); ramp 100%/min; 6% min CF; 5% forced & scheduled outage; 0 start cost; zero direct CO₂/SO₂.
• Per-technology h2-fuel-cell rows were added across the plant-characteristic and financial input files (emitrate, cost_opres_default/_market, minCF, mttr, outage_forced_static, outage_scheduled_static, ramprate, startcost, unitsize_atb, heat_rate_adj, heat_rate_penalty_spin, degradation_annual_default, years_until_endogenous, construction_times_default, financials_tech_ATB2023/_CRP20/ATB2024, reg_cap_cost_diff_default, nat_gen_tech_frac, ivt_default/_small/_step, futurefiles, runfiles).

Additional changes

• postprocessing/tech_aggregation.csv, tech_map.csv, tech_style.csv updated for h2-fuel-cell display: mapped to H2-Fuel-Cell, aggregated as "H2 Fuel Cell", color #87A21D. (A matching H2 Fuel Cell style key was added so the aggregated bar renders in compare_cases.py PPTs.)
• cases_h2-fuelcell.csv added with 5 test scenarios: USA_defaults_fc_pr (runs without fc switch turning on), USA_defaults_fc_mid (moderate cost/deployment cost case), USA_defaults_fc_low (advanced/high deployment cost case), USA_defaults_fc_high (conservative/low deployment cost case), USA_defaults_fc_mid_w_ng_fc (moderate level + NG fuel cell switch turned on).
• Documentation: new "Hydrogen fuel cells" subsection in docs/source/model_documentation.md, file entries in sources.md, and a Reznicek 2026 entry in references.bib.

Switches added/removed/changed

Switch	Values	Default	Description
GSw_H2FuelCell	0, 1	0	New — enables h2-fuel-cell as a technology option
plantchar_h2fuelcell	h2fuelcell_conservative, h2fuelcell_moderate, h2fuelcell_advanced	h2fuelcell_moderate	New — H2 fuel cell cost and performance scenario

(GSw_FuelCell is unchanged by this PR and continues to govern only ng-fuel-cell.)

Relevant sources or documentation

• Reznicek, E., Berres, A., Li, Y., et al., Cost Analysis of Heavy-Duty Vehicle Proton Exchange Membrane Fuel Cell Stationary Power Plants (2026), https://doi.org/10.2172/3018256 — unit size and performance parameters

Validation, testing, and comparison report(s)

Ran 1/6 cases under main ReEDS branch, also ran the 5/6 cases under cases_h2-fuelcell.csv to test scenarios (fc_pr, fc_low, fc_mid, fc_high, fc_mid_w_ng_fc) and compared capacity, location, and dispatch with compare_cases.py. The new h2-fuel-cell technology builds, is selected over H2-CT as costs decline, and dispatches as expected.

Location & technology selection (2030)

In 2030 the H2 capacity lands in exactly two BAs : p10 (692 MW) and p31 (210 MW) = 902 MW total in every scenario. The location does not change; only the technology filling those two slots swaps between scenarios as the fuel-cell cost case improves:

Scenario	p10 (692 MW)	p31 (210 MW)
fc_pr	H2-CT	H2-CT
fc_low	fuel cell	fuel cell
fc_mid	fuel cell	fuel cell
fc_mid_w_ng_fc	fuel cell	fuel cell
fc_high	fuel cell	H2-CT

This 902 MW is prescribed build from inputs/capacity_exogenous/interconnection_queues.csv . It appears as a step in 2030 in p10 + p31, holds flat through 2035, then declines. The model fills that prescribed requirement with the cheapest available H2 technology, which is why fuel cell displaces H2-CT in the cheaper cost cases (low/mid), partially in high (p10 only), and not at all in pr (H2-CT baseline).

H2 fuel cell capacity build (MW)

Scenario	2025	2030	2035	2040	2045	2050
pr	0	0	0	0	0	0
low	0	902	902	847	389	140
mid	0	902	902	842	384	138
high	0	692	692	524	256	52

Dispatch / capacity factor

Annual CF is a flat 6.0% across every scenario and year. The 6% is the annual minimum CF requirement imposed in inputs/plant_characteristics/minCF.csv; peak hourly utilization reaches ~16% max when looking at the gen_h.csv file.

Checklist for author

Details to double-check

• References for all H2 fuel cell operational data (Reznicek et al. 2026, DOI 10.2172/3018256)
• 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 h2fuelcell_* scenarios, 2022$)
  • Units specified (MW capacity, $/kW capex, $/kW-yr FOM, $/MWh VOM, MMBtu/MWh heat rate)
  • 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_H2FuelCell=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 documentation modification and writing this PR language.

Tag points of contact

@yijinli22

[louisaserpe]

Thanks Yijin! Let me know if you have any questions or need help with any of these changes.

[louisaserpe]

Can you round to 3 decimal places?

[louisaserpe]

Can you round to 3 decimals?

[louisaserpe]

Can you point me to where these fom and vom numbers are coming from? The paper says we assume the same vom and fom as NG CTs but these values don't match the ATB/gas_ATB_2024_moderate

[louisaserpe]

Just documenting that I checked that this is HHV

[louisaserpe]

Do we need both here?

[louisaserpe]

Suggested change

	h2-fuel-cell,H2-Fuel-Cell,H2 Fuel Cell,Thermal,H2-Fuel-Cell
	h2-fuel-cell,H2-Fuel-Cell,Hydrogen Combustion,Remove,H2-Fuel-Cell

[louisaserpe]

Suggested change

	GSw_H2Combustion,Switch to turn on/off H2CT , H2CC, H2 FUEL CELL techs,0; 1,1,

[louisaserpe]

Since h2-fuel-cell is marked as YES under H2_COMBUSTION in tech-subset-table, fuel cells will be listed as a banned technology if GSw_H2Combustion is not also turned on. I would add a check in the runreeds.py check_compatibility function to ensure a user has both turned on when trying to include H2 fuel cells as an option

[louisaserpe]

Let's delete this file before merging into main. I'd suggest adding a small fuel cell case to either the cases_example.csv or cases_test.csv