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Rollback support for multiple construction years for SAM-EM for now. Meaningful and logically/conceptually consistent support will require deeper changes than just auto-calculating inflation costs, such as accounting for cost of construction financing. Created tracking issue NREL#406 
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‎docs/Fervo_Project_Cape-4.md

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@@ -54,14 +54,14 @@ in source code for the full set of inputs.
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| Fraction of Investment in Bonds (percent debt vs. equity) | 60% | Approximate remaining percentage of CAPEX with $1 billion sponsor equity per Matson, 2024. Note that this source says that Fervo ultimately wants to target "15% sponsor equity, 15% bridge loan, and 70% construction to term loans", but this case study does not attempt to model that capital structure. |
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| Exploration Capital Cost | $30M | Estimate significantly higher exploration costs than default correlation in consideration of potential risks associated with second/third/fourth-of-a-kind EGS projects |
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| Investment Tax Credit Rate (ITC) | 30% | Same as 400 MWe case study (Fervo_Project_Cape-3) |
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| Inflation Rate During Construction | 15% | Models a higher annual inflation rate (4.769%) over the 3-year construction period as a hedge against short-term inflation volatility. |
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| Inflation Rate During Construction | 15% | Conservatively models the equivalent of a higher annual inflation rate (4.769%) over a 3-year period as a hedge against construction delays and short-term inflation volatility. |
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### Technical & Engineering Parameters
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| Parameter | Input Value(s) | Source |
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|-------------------------------|----------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| Plant Lifetime | 30 years | 30-year well life per Fervo Energy, 2025 (Geothermal Mythbusting: Water Use and Impacts). |
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| Construction time | 3 years | Calibrated to a 2-6 year construction time for a 1 GW plant (Yusifov & Enriquez, 2025). |
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| Construction time | 1 year | Calibrated to a 2–6 year construction time for a 1 GW plant (Yusifov & Enriquez, 2025). Note that the Inflation Rate During Construction parameter hedges against potential construction delays. |
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| Well diameter | 9⅝ inches | Next standard size up from 7", implied by announcement of "increasing casing diameter" |
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| Flow Rate per Production Well | 107 kg/s | Fercho et al, 2025 models reservoir performance using 100 kg/s per well. The announced increased casing diameter implies higher flow rates, so the case study uses the maximum flow rate achieved at Cape Station of 107 kg/s per Fervo Energy, 2024. |
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| Number of Doublets | 59 | Estimate based on extrapolation from previous case studies including [Project Red](https://gtp.scientificwebservices.com/geophires/?geophires-example-id=Fervo_Norbeck_Latimer_2023) and [Fervo_Project_Cape-3](https://gtp.scientificwebservices.com/geophires/?geophires-example-id=Fervo_Project_Cape-3) |

‎docs/SAM-Economic-Models.md

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@@ -48,6 +48,7 @@ The following table describes how GEOPHIRES parameters are transformed into SAM
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### Limitations
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1. Only Electricity end-use is supported
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2. Only 1 construction year is supported. Note that the `Inflation Rate During Construction` parameter can be used to partially account for longer construction periods.
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## Using SAM Economic Models with Existing GEOPHIRES Inputs
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‎src/geophires_x/EconomicsSam.py

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@@ -92,6 +92,15 @@ def _inv_msg(param_name: str, invalid_value: Any, supported_description: str) ->
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)
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)
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if model.surfaceplant.construction_years.value != 1:
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raise ValueError(
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_inv_msg(
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model.surfaceplant.construction_years.Name,
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model.surfaceplant.construction_years.value,
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f'{model.surfaceplant.construction_years.Name} = 1',
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)
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)
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gtr: floatParameter = model.economics.GTR
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if gtr.Provided:
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model.logger.warning(

‎src/geophires_x/EconomicsSamCashFlow.py

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@@ -22,6 +22,9 @@ def _calculate_sam_economics_cash_flow(model: Model, single_owner: Singleowner)
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_soo = single_owner.Outputs
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profile = []
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# TODO this and/or related logic will need to be adjusted when multiple construction years are supported
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# https://github.com/NREL/GEOPHIRES-X/issues/406
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total_duration = model.surfaceplant.plant_lifetime.value + model.surfaceplant.construction_years.value
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# Prefix with 'Year ' partially as workaround for tabulate applying float formatting to ints, possibly related

‎tests/examples/Fervo_Project_Cape-4.out

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Simulation Metadata
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----------------------
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GEOPHIRES Version: 3.9.40
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Simulation Date: 2025-07-26
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Simulation Time: 14:13
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Calculation Time: 1.709 sec
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GEOPHIRES Version: 3.9.41
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Simulation Date: 2025-07-27
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Simulation Time: 11:26
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Calculation Time: 1.738 sec
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***SUMMARY OF RESULTS***
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***************************
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* SAM CASH FLOW PROFILE *
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***************************
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-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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Year 0 Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Year 11 Year 12 Year 13 Year 14 Year 15 Year 16 Year 17 Year 18 Year 19 Year 20 Year 21 Year 22 Year 23 Year 24 Year 25 Year 26 Year 27 Year 28 Year 29 Year 30 Year 31 Year 32
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-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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Year 0 Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Year 11 Year 12 Year 13 Year 14 Year 15 Year 16 Year 17 Year 18 Year 19 Year 20 Year 21 Year 22 Year 23 Year 24 Year 25 Year 26 Year 27 Year 28 Year 29 Year 30
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ENERGY
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Electricity to grid (kWh) 0.0 4,193,273,525 4,219,573,970 4,227,516,388 4,232,001,035 4,233,245,126 4,225,570,913 4,194,325,606 4,114,710,394 4,101,737,992 4,212,547,398 4,224,519,385 4,230,441,060 4,233,667,186 4,231,750,368 4,214,888,525 4,163,207,043 4,055,985,743 4,194,671,056 4,220,853,770 4,228,811,003 4,233,321,393 4,234,588,146 4,226,928,684 4,195,686,141 4,116,056,232 4,103,061,353 4,213,834,812 4,225,738,401 4,231,569,184 4,234,649,495
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Electricity from grid (kWh) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
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Reserves total reserves balance ($) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
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Interest on reserves (%/year) 1.75
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Interest earned on reserves ($) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
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-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

‎tests/examples/Fervo_Project_Cape-4.txt

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Inflation Rate, .023, -- US inflation as of April 2025
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Inflation Rate During Construction, 0.15, -- Models a higher annual inflation rate (4.769%) over the 3-year construction period as a hedge against short-term inflation volatility.
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Construction Years, 3, -- Calibrated to a 2-6 year construction time for a 1 GW plant (Yusifov & Enriquez, 2025)
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Construction Years, 1, -- Calibrated to a 2-6 year construction time for a 1 GW plant (Yusifov & Enriquez, 2025)
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Combined Income Tax Rate, .28

‎tests/geophires_x_tests/generic-egs-case-3_no-inflation-rate-during-construction.txt

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@@ -39,9 +39,7 @@ Electricity Escalation Rate Per Year, 0.004053223
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Electricity Escalation Start Year, 1
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Fraction of Investment in Bonds, .5
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Combined Income Tax Rate, .3
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Gross Revenue Tax Rate, 0
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Inflated Bond Interest Rate, .05
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Inflated Equity Interest Rate, .08
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Inflation Rate, .02
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Investment Tax Credit Rate, .3, -- https://programs.dsireusa.org/system/program/detail/658
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Production Tax Credit Electricity, 0.0275, -- https://programs.dsireusa.org/system/program/detail/734

‎tests/geophires_x_tests/test_economics_sam.py

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self.assertIn('Invalid End-Use Option (Direct-Use Heat)', str(e.exception))
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def test_multiple_construction_years_supported(self):
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self.assertIsNotNone(self._get_result({'Construction Years': 2}))
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def test_only_1_construction_year_supported(self):
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# TODO remove this test and uncomment test_multiple_construction_years_supported below once multiple
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# construction years are supported https://github.com/NREL/GEOPHIRES-X/issues/406
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with self.assertRaises(RuntimeError) as e:
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self._get_result({'Construction Years': 2})
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self.assertIn('Invalid Construction Years (2)', str(e.exception))
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self.assertIn('SAM_SINGLE_OWNER_PPA only supports Construction Years = 1.', str(e.exception))
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# def test_multiple_construction_years_supported(self):
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# self.assertIsNotNone(self._get_result({'Construction Years': 2}))
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def test_ppa_pricing_model(self):
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self.assertListEqual(
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return _r.result['ECONOMIC PARAMETERS']['Accrued financing during construction']['value']
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params1 = {
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'Construction Years': 3,
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'Construction Years': 1,
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'Inflation Rate': 0.04769,
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}
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r1: GeophiresXResult = self._get_result(
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params1, file_path=self._get_test_file_path('generic-egs-case-3_no-inflation-rate-during-construction.txt')
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)
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self.assertEqual(15.0, _accrued_financing(r1))
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self.assertAlmostEqual(4.769, _accrued_financing(r1), places=1)
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params2 = {
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'Construction Years': 3,
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'Construction Years': 1,
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'Inflation Rate During Construction': 0.15,
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}
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r2: GeophiresXResult = self._get_result(
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params2, file_path=self._get_test_file_path('generic-egs-case-3_no-inflation-rate-during-construction.txt')
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)
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self.assertEqual(15.0, _accrued_financing(r2))
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# TODO enable when multiple construction years are supported https://github.com/NREL/GEOPHIRES-X/issues/406
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# params3 = {
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# 'Construction Years': 3,
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# 'Inflation Rate': 0.04769,
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# }
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# r3: GeophiresXResult = self._get_result(
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# params3, file_path=self._get_test_file_path('generic-egs-case-3_no-inflation-rate-during-construction.txt')
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# )
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# self.assertEqual(15.0, _accrued_financing(r3))
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#
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# params4 = {
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# 'Construction Years': 3,
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# 'Inflation Rate During Construction': 0.15,
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# }
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# r4: GeophiresXResult = self._get_result(
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# params4, file_path=self._get_test_file_path('generic-egs-case-3_no-inflation-rate-during-construction.txt')
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# )
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# self.assertEqual(15.0, _accrued_financing(r4))
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@staticmethod
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def _new_model(input_file: Path, additional_params: dict[str, Any] | None = None, read_and_calculate=True) -> Model:
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if additional_params is not None:

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