Thermodynamic NGCT model by cfrontin · Pull Request #805 · NatLabRockies/H2Integrate

cfrontin · 2026-07-20T17:35:52Z

Thermodynamic models for NGCT (w/ support for future `combustion_machines`)

The performance of combustion machines, including both combustion turbines, combined cycle turbines, and reciprocating internal combustion engines, has significant dependence on ambient conditions (real time and design-specified).

These models use standard thermodynamic cycles to increase the fidelity of ICE combustion systems in H2I. These are critical for understanding complementarity of renewables and fuel combustion systems in hybrid energy generation, where ambient conditions determine the performance of nominally firm power sources as well as renewables, often in mutually complimentary ways.

Demonstration of code addendum showing diurnal and seasonal performance cycles as a function of ambient pressure and temperature.

Section 1: Type of Contribution

Section 2: Draft PR Checklist

Open draft PR
Describe the feature that will be added
Fill out TODO list steps
Describe requested feedback from reviewers on draft PR
Complete Section 7: New Model Checklist (if applicable)

TODO:

remove debug runner script
add upgraded cost model w/ fuel-consumption driven costs
develop example case(s)

Type of Reviewer Feedback Requested (on Draft PR)

Structural feedback:

Implementation feedback:

Other feedback:

Section 3: General PR Checklist

Section 4: Related Issues

Section 5: Impacted Areas of the Software

Section 5.1: New Files

h2integrate/converters/combustion_machines/__init__.py
- allow import
h2integrate/converters/combustion_machines/NGCT_thermo_model.py
- isolate thermodynamic modeling for independent testing w.r.t. H2I wrapper
h2integrate/converters/combustion_machines/test_NGCT_thermo_model.py
- isolated testing for purely single-system thermodynamic modeling
h2integrate/converters/combustion_machines/turbine_simple_cycle.py
- the H2I wrapper for the NGCT model

Section 5.2: Modified Files

h2integrate/core/supported_models.py
- added new converter performance & cost model

Section 6: Additional Supporting Information

Section 7: Test Results, if applicable

Section 8 (Optional): New Model Checklist

…eature/thermodynamic_NGCT_model

cfrontin · 2026-07-20T22:54:39Z

I've added both the optional dependency as well as the mainline dependency here; one should be removed, at the discretion of the H2I devs. I actually thought at first (said this to @johnjasa) that pyfluids was already in the dependency chain, but I was apparently incorrect in that understanding.

…matting

…n/H2Integrate into feature/thermodynamic_NGCT_model

johnjasa · 2026-07-27T17:23:12Z

 extras = ["h2integrate[gis,ard]"]
 all = ["h2integrate[develop,extras,examples]"]


Suggested change

extras = ["h2integrate[gis,ard]"]

all = ["h2integrate[develop,extras,examples]"]

extras = ["h2integrate[gis,ard,thermo]"]

all = ["h2integrate[develop,extras,examples]"]

kbrunik

@cfrontin this is super exciting stuff, I like the linking of resource data to other models that have been rather simplistically modeled up to this point. I left a few comments and thoughts, but overall, it's really great

kbrunik · 2026-07-28T20:52:37Z

+    state_outlet,
+    mass_flow_fluid=1.0,  # by default unity, returns unit-mass kJ/kg
+):
+    # heat transfer to a system should be positive


Should there be a user warning or error message if this isn't true?

kbrunik · 2026-07-28T20:53:39Z

+    return state_outlet
+
+
+class ThermodynamicCycleResult:


could you add a docstring to this?

kbrunik · 2026-07-28T21:33:36Z

+
+
+@define(kw_only=True)
+class SimpleCycleTurbinePerformanceConfig(BaseConfig):


It seems useful to add design_conditions as an input to the config to be able to use all of the functionality of the NGCT model

kbrunik · 2026-07-28T21:36:08Z

+        return float(np.min(mass_flowrate_candidates))
+
+
+class GE_7FA05_NGCT(NGCT):


I'd be inclined to see the GE_7FA05_NGCT and GE_7EA_NGCT_2014 classes be converted to yaml files for easy inclusion when running the SimpleCycleTurbinePerformanceModel. It seems right now their functionality is limited to this particular file and not as something that would be able to be used within the larger H2I system.

kbrunik · 2026-07-28T21:38:36Z

+    )  # (min, max) time step lengths (in seconds) compatible with this model
+    _control_classifier = "dispatchable"
+
+    def initialize(self, fuel_source="natural_gas"):


Is there a reason to initialize the fuel_source here vs using the typical feedstocks? Is this to limit the fuel source type?

kbrunik · 2026-07-28T21:40:34Z

+            m * q for m, q in zip(mass_flowrates, unit_mass_net_heat_input_vec)
+        ]  # kJ/s
+
+        # import matplotlib.pyplot as plt


You could functionalize this and add a show_plots attribute to the base config for folks to be able to see these outputs if they want.

kbrunik · 2026-07-28T21:52:08Z

+            Q_fluid_max=1.0,  # (explicitly) unit-mass analysis
+        )
+
+        # try to run NGCT cycle here expensively, and all compute variations


Is there that big of a computational advantage precomputing this in the setup method versus using the given temperature and pressure data based on the solar resource in the actual compute method? It seems slightly redundant but maybe I'm missing something?

kbrunik · 2026-07-28T21:52:58Z

+                for T, P in wx_data
+            ]
+            self.fundamental_cycle = self.ngct.run_turbine_model(self.ambient_fluid_list)
+            # print("DEBUG!!!!! RE-COMPUTING UNIT-MASS CYCLE B/C AMBIENT FLUID STATES CHANGED")


can we remove these print statements but keep the comment of what's happening in the if statement?

kbrunik · 2026-07-28T21:53:49Z

+        )
+
+
+if __name__ == "__main__":


I'd love to see this as a test and remove everything after if __name__ == "__main__": in this file

elenya-grant

This is just a partial review that I wanted to submit before reviewing the whole thing! Mostly had minor questions and suggestions! I can do a more full review later!

elenya-grant · 2026-07-28T21:46:15Z

+    Attributes:
+    -----------


Suggested change

Attributes:

-----------

Attributes:

elenya-grant · 2026-07-28T21:47:58Z

+    )  # (min, max) time step lengths (in seconds) compatible with this model
+    _control_classifier = "dispatchable"
+
+    def initialize(self, fuel_source="natural_gas"):


Could this fuel_source input be removed from the initialize() method and be moved as an input to the SimpleCycleTurbinePerformanceConfig? With a contains validator?

elenya-grant · 2026-07-28T21:50:39Z

+        self.ngct = NGCT.NGCT(
+            ratio_P=self.config.pressure_ratio,
+            Trel_firing=self.config.firing_temp_C,
+            isentropic_efficiency_compressor=self.config.isentropic_efficiency_compressor,
+            isentropic_efficiency_turbine=self.config.isentropic_efficiency_turbine,
+            Q_fluid_max=1.0,  # (explicitly) unit-mass analysis
+        )


would any of the inputs to NGCT be optimization variables or swept in a parameter sweep for any foreseeable use-case? If so - then I think these should be inputs and then this could be moved to the compute() method.

elenya-grant · 2026-07-28T21:52:06Z

+
+        # extract from the solar resource data
+        temperature_degC = discrete_inputs["solar_resource_data"]["temperature"]
+        pressure_Pa = (


I think the pressure data output by the solar resource data defaults to mbar - not hPa?

elenya-grant · 2026-07-28T21:52:54Z

+        else:
+            pass


Suggested change

else:

pass

elenya-grant · 2026-07-28T21:55:52Z

this file should live in h2integrate/converters/combustion_machines/test/

elenya-grant · 2026-07-28T21:57:13Z

+            val=0.0,
+            shape=self.n_timesteps,
+            units="kJ/s",
+            desc="fuel input energy to the turbine/plant in MMBtu/h",


description says different units than the units defined. I'd suggestion removing the MMbBtu/h part from the description.

elenya-grant · 2026-07-28T22:01:20Z

+        # try to run NGCT cycle here expensively, and all compute variations
+        # should be derivable w/o major new computation after that
+        P_ambient = 101325.0  # Pa
+        T_ambient = 15.0  # °C
+        self.working_fluid = NGCT.pyfluids.Fluid(NGCT.pyfluids.FluidsList.Air)
+        wx_data = [(T_ambient, P_ambient)]
+        self.wx_checksums = [hash(wxd) for wxd in wx_data]
+        self.ambient_fluid_list = [
+            self.working_fluid.with_state(
+                NGCT.pyfluids.Input.pressure(P),
+                NGCT.pyfluids.Input.temperature(T),
+            )
+            for T, P in wx_data
+        ]
+        self.fundamental_cycle = self.ngct.run_turbine_model(self.ambient_fluid_list)


I'm confused by this comment and the code itself. If the first run is always with the ambient temperature and pressure - then the self.wx_checksums and wx_checksums will always be different the first time compute() is called. Why not just initialize the self.wx_checksums to a list of empty strings or Nones and not run the NGCT model in the setup() method?

elenya-grant · 2026-07-29T16:17:10Z

+        )
+
+
+if __name__ == "__main__":


reminder to remove this before it gets merged

cfrontin added 3 commits July 17, 2026 23:01

progress toward NGCT thermodynamic model in H2I

b0db08f

updated ngct for cleanliness

e4da055

Merge branch 'develop' of github.com:NatLabRockies/H2Integrate into f…

8db14e5

…eature/thermodynamic_NGCT_model

cfrontin changed the title ~~Feature/thermodynamic ngct model~~ Thermodynamic NGCT model Jul 20, 2026

precommit fixes

9eac59e

jaredthomas68 self-requested a review July 20, 2026 20:43

cfrontin added 2 commits July 20, 2026 16:48

add pyfluids dependency

abeece6

pyfluids to main deps but also with optional

06d8f17

cfrontin commented Jul 20, 2026

View reviewed changes

cfrontin and others added 4 commits July 21, 2026 13:39

Merge branch 'develop' into feature/thermodynamic_NGCT_model

cfe2690

prep for generalization of code for recip. engines, apply black refor…

54f26b5

…matting

Merge branch 'feature/thermodynamic_NGCT_model' of github.com:cfronti…

413b040

…n/H2Integrate into feature/thermodynamic_NGCT_model

Merge branch 'develop' into feature/thermodynamic_NGCT_model

68fc6cf

johnjasa reviewed Jul 27, 2026

View reviewed changes

kbrunik requested changes Jul 28, 2026

View reviewed changes

elenya-grant reviewed Jul 30, 2026

View reviewed changes

		extras = ["h2integrate[gis,ard]"]
		all = ["h2integrate[develop,extras,examples]"]



		@define(kw_only=True)
		class SimpleCycleTurbinePerformanceConfig(BaseConfig):

		return float(np.min(mass_flowrate_candidates))


		class GE_7FA05_NGCT(NGCT):

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Thermodynamic models for NGCT (w/ support for future combustion_machines)

Section 1: Type of Contribution

Section 2: Draft PR Checklist

TODO:

Type of Reviewer Feedback Requested (on Draft PR)

Section 3: General PR Checklist

Section 4: Related Issues

Section 5: Impacted Areas of the Software

Section 5.1: New Files

Section 5.2: Modified Files

Section 6: Additional Supporting Information

Section 7: Test Results, if applicable

Section 8 (Optional): New Model Checklist

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cfrontin commented Jul 20, 2026 •

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Thermodynamic models for NGCT (w/ support for future `combustion_machines`)