Initial implementation of royalty rate. WIP - TODO to implement royalty collector revenue/NPV/etc., update documentation, add more unit tests

Author: softwareengineerprogrammer

src/geophires_x/Economics.py

@@ -967,6 +967,16 @@ def __init__(self, model: Model):
                         "will be automatically set to the same value."
         )
 
+        self.royalty_rate = self.ParameterDict[self.royalty_rate.Name] = floatParameter(
+            "Royalty Rate",
+            DefaultValue=0.,
+            Min=0.0,
+            Max=1.0,
+            UnitType=Units.PERCENT,
+            PreferredUnits=PercentUnit.TENTH,
+            CurrentUnits=PercentUnit.TENTH,
+            ToolTipText="Royalty rate used in SAM Economic Models."  # FIXME WIP TODO documentation
+        )
 
         self.discount_initial_year_cashflow = self.ParameterDict[self.discount_initial_year_cashflow.Name] = boolParameter(
             'Discount Initial Year Cashflow',

src/geophires_x/EconomicsSam.py

@@ -395,13 +395,29 @@ def _get_single_owner_parameters(model: Model) -> dict[str, Any]:
     geophires_ptr_tenths = Decimal(econ.PTR.value)
     ret['property_tax_rate'] = float(geophires_ptr_tenths * Decimal(100))
 
-    ret['ppa_price_input'] = _ppa_pricing_model(
+    ppa_price_schedule_per_kWh = _ppa_pricing_model(
         model.surfaceplant.plant_lifetime.value,
         econ.ElecStartPrice.value,
         econ.ElecEndPrice.value,
         econ.ElecEscalationStart.value,
         econ.ElecEscalationRate.value,
     )
+    ret['ppa_price_input'] = ppa_price_schedule_per_kWh
+
+    if hasattr(econ, 'royalty_rate') and econ.royalty_rate.value > 0.0:
+        royalty_rate_fraction = econ.royalty_rate.quantity().to(convertible_unit('dimensionless')).magnitude
+
+        # For each year, calculate the royalty as a $/MWh variable cost.
+        # The royalty is a percentage of revenue (MWh * $/MWh). By setting the
+        # variable O&M rate to (PPA Price * Royalty Rate), SAM's calculation
+        # (Rate * MWh) will correctly yield the total royalty payment.
+        variable_om_schedule_per_MWh = [
+            (price_per_kWh * 1000) * royalty_rate_fraction  # TODO pint unit conversion (kWh -> MWh)
+            for price_per_kWh in ppa_price_schedule_per_kWh
+        ]
+
+        # The PySAM parameter for variable operating cost in $/MWh is 'om_production'.
+        ret['om_production'] = variable_om_schedule_per_MWh
 
     # Debt/equity ratio ('Fraction of Investment in Bonds' parameter)
     ret['debt_percent'] = _pct(econ.FIB)

src/geophires_x/Units.py

@@ -26,6 +26,9 @@ def convertible_unit(unit: Any) -> Any:
     if unit == Units.PERCENT or unit == PercentUnit.PERCENT or unit == Units.PERCENT.value:
         return 'percent'
 
+    if unit == PercentUnit.TENTH or unit == PercentUnit.TENTH.value:
+        return 'dimensionless'
+
     return unit
 
 

tests/geophires_x_tests/test_economics_sam.py

@@ -638,6 +638,24 @@ def _assert_capex_line_items_sum_to_total(self, r: GeophiresXResult):
 
         self.assertEqual(total_capex, capex_line_item_sum)
 
+    def test_royalty_rate(self):
+        royalty_rate = 0.1
+        m: Model = EconomicsSamTestCase._new_model(
+            self._egs_test_file_path(), additional_params={'Royalty Rate': royalty_rate}
+        )
+
+        sam_econ = calculate_sam_economics(m)
+        cash_flow = sam_econ.sam_cash_flow_profile
+
+        def get_row(name: str):
+            return EconomicsSamTestCase._get_cash_flow_row(cash_flow, name)
+
+        ppa_revenue_row = get_row('PPA revenue ($)')
+        expected_royalties = [x * royalty_rate for x in ppa_revenue_row]
+
+        om_prod_based_expense_row = get_row('O&M production-based expense ($)')
+        self.assertListAlmostEqual(expected_royalties, om_prod_based_expense_row, places=0)
+
     @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: