Calculate SAM NaN After-tax IRRs using numpy-financial.irr

Author: softwareengineerprogrammer

src/geophires_x/EconomicsSam.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import json
+import math
 import os
 from dataclasses import dataclass, field
 from functools import lru_cache
@@ -11,6 +12,7 @@
 from decimal import Decimal
 
 import numpy as np
+import numpy_financial as npf
 
 # noinspection PyPackageRequirements
 from PySAM import CustomGeneration
@@ -155,12 +157,13 @@ def calculate_sam_economics(model: Model) -> SamEconomicsCalculations:
 
     cash_flow = _calculate_sam_economics_cash_flow(model, single_owner)
 
-    def sf(_v: float) -> float:
-        return _sig_figs(_v, 5)
+    def sf(_v: float, num_sig_figs: int = 5) -> float:
+        return _sig_figs(_v, num_sig_figs)
 
     sam_economics: SamEconomicsCalculations = SamEconomicsCalculations(sam_cash_flow_profile=cash_flow)
     sam_economics.lcoe_nominal.value = sf(single_owner.Outputs.lcoe_nom)
-    sam_economics.after_tax_irr.value = sf(single_owner.Outputs.project_return_aftertax_irr)
+    sam_economics.after_tax_irr.value = sf(_get_after_tax_irr_pct(single_owner, cash_flow, model))
+
     sam_economics.project_npv.value = sf(single_owner.Outputs.project_return_aftertax_npv * 1e-6)
     sam_economics.capex.value = single_owner.Outputs.adjusted_installed_cost * 1e-6
 
@@ -171,6 +174,25 @@ def sf(_v: float) -> float:
     return sam_economics
 
 
+def _get_after_tax_irr_pct(single_owner: Singleowner, cash_flow: list[list[Any]], model: Model) -> float:
+    after_tax_irr_pct = single_owner.Outputs.project_return_aftertax_irr
+    if math.isnan(after_tax_irr_pct):
+        try:
+
+            def cash_flow_profile_row(row_name: str) -> list[Any]:
+                return next(  # type: ignore[no-any-return]
+                    row for row in cash_flow if len(row) > 0 and row[0] == row_name
+                )[1:]
+
+            after_tax_returns_cash_flow = cash_flow_profile_row('Total after-tax returns ($)')
+            after_tax_irr_pct = npf.irr(after_tax_returns_cash_flow) * 100.0
+            model.logger.info(f'After-tax IRR was NaN, calculated with numpy-financial: {after_tax_irr_pct}%')
+        except Exception as e:
+            model.logger.warning(f'After-tax IRR was NaN and calculation with numpy-financial failed: {e}')
+
+    return after_tax_irr_pct
+
+
 def _calculate_nominal_discount_rate_and_wacc(model: Model, single_owner: Singleowner) -> tuple[float]:
     """
     Calculation per SAM Help -> Financial Parameters -> Commercial -> Commercial Loan Parameters -> WACC

src/geophires_x/EconomicsUtils.py

@@ -45,7 +45,9 @@ def after_tax_irr_parameter() -> OutputParameter:
         PreferredUnits=PercentUnit.PERCENT,
         ToolTipText='The After-tax IRR (internal rate of return) is the nominal discount rate that corresponds to '
                     'a net present value (NPV) of zero for PPA SAM Economic models. '
-                    'See https://samrepo.nrelcloud.org/help/mtf_irr.html.'
+                    'See https://samrepo.nrelcloud.org/help/mtf_irr.html. If SAM calculates After-tax IRR as NaN, '
+                    'numpy-financial.irr (https://numpy.org/numpy-financial/latest/irr.html) '
+                    'is used to calculate the value from SAM\'s total after-tax returns.'
     )
 
 

src/geophires_x_schema_generator/geophires-result.json

@@ -17,6 +17,7 @@
           "description": "LCOE. For SAM economic models, this is the nominal LCOE value (as opposed to real).",
           "units": "cents/kWh"
         },
+        "Total CAPEX": {},
         "Average Direct-Use Heat Production": {},
         "Direct-Use heat breakeven price": {},
         "Direct-Use heat breakeven price (LCOH)": {
@@ -104,7 +105,7 @@
         },
         "After-tax IRR": {
           "type": "number",
-          "description": "The After-tax IRR (internal rate of return) is the nominal discount rate that corresponds to a net present value (NPV) of zero for PPA SAM Economic models. See https://samrepo.nrelcloud.org/help/mtf_irr.html.",
+          "description": "The After-tax IRR (internal rate of return) is the nominal discount rate that corresponds to a net present value (NPV) of zero for PPA SAM Economic models. See https://samrepo.nrelcloud.org/help/mtf_irr.html. If SAM calculates After-tax IRR as NaN, numpy-financial.irr (https://numpy.org/numpy-financial/latest/irr.html) is used to calculate the value from SAM's total after-tax returns.",
           "units": "%"
         },
         "Project VIR=PI=PIR": {
@@ -254,6 +255,7 @@
           "description": "Calculated Fracture Separation",
           "units": "meter"
         },
+        "Reservoir volume calculation note": {},
         "Reservoir volume": {},
         "Reservoir impedance": {},
         "Reservoir hydrostatic pressure": {},

tests/geophires_x_tests/test_economics_sam.py

@@ -1,11 +1,13 @@
 from __future__ import annotations
 
+import math
 import os
 import sys
 from pathlib import Path
 from typing import Any
 
 import numpy as np
+import numpy_financial as npf
 
 from base_test_case import BaseTestCase
 
@@ -466,6 +468,38 @@ def test_get_fed_and_state_tax_rates(self):
         self.assertEqual(([21], [9]), _get_fed_and_state_tax_rates(0.3))
         self.assertEqual(([10], [0]), _get_fed_and_state_tax_rates(0.1))
 
+    def test_nan_after_tax_irr(self):
+        """
+        Verify that After-tax IRRs that would have been calculated as NaN by SAM are instead calculated with
+        numpy-financial.irr
+        """
+
+        def _irr(_r: GeophiresXResult) -> float:
+            return _r.result['ECONOMIC PARAMETERS']['After-tax IRR']['value']
+
+        rate_params = {
+            'Electricity Escalation Rate Per Year': 0.00348993288590604,
+            'Starting Electricity Sale Price': 0.13,
+        }
+        r: GeophiresXResult = self._get_result(rate_params)
+        after_tax_irr_cash_flow_entries = EconomicsSamTestCase._get_cash_flow_row(
+            r.result['SAM CASH FLOW PROFILE'], 'After-tax cumulative IRR (%)'
+        )
+        sam_after_tax_irr_calc = float(after_tax_irr_cash_flow_entries[-1])
+
+        # Test case condition - we expect SAM to have calculated NaN here. If this assertion fails, adjust params passed
+        # to _get_result such that final year of After-tax cumulative IRR is NaN.
+        assert math.isnan(sam_after_tax_irr_calc)
+
+        after_tax_cash_flow = EconomicsSamTestCase._get_cash_flow_row(
+            r.result['SAM CASH FLOW PROFILE'], 'Total after-tax returns ($)'
+        )
+        npf_irr = npf.irr(after_tax_cash_flow) * 100.0
+
+        r_irr = _irr(r)
+        self.assertFalse(math.isnan(r_irr))
+        self.assertAlmostEqual(npf_irr, r_irr, places=2)
+
     @staticmethod
     def _new_model(input_file: Path, additional_params: dict[str, Any] | None = None, read_and_calculate=True) -> Model:
         if additional_params is not None: