fix unit test failure introduced in d6966a6 by keeping electricity rate percent constant

Author: softwareengineerprogrammer

src/geophires_x/EconomicsSam.py

@@ -27,6 +27,7 @@
 from geophires_x.Units import convertible_unit
 
 _SAM_CASH_FLOW_PROFILE_KEY = 'Cash Flow'
+_GEOPHIRES_TO_SAM_PRICING_MODEL_RATE_CONVERSION_CONSTANT = 0.745
 
 
 @lru_cache(maxsize=12)
@@ -132,7 +133,12 @@ def _get_single_owner_parameters(model: Model) -> dict[str, Any]:
 
     ret['ppa_price_input'] = [econ.ElecStartPrice.value]
     # Approximation of GEOPHIRES rate model into SAM's percent inflation model (TODO - could probably be improved)
-    ppa_escalation_rate_percent = round(econ.ElecEscalationRate.value / econ.ElecStartPrice.value * 0.745 * 100.0)
+    ppa_escalation_rate_percent = round(
+        econ.ElecEscalationRate.value
+        / econ.ElecStartPrice.value
+        * _GEOPHIRES_TO_SAM_PRICING_MODEL_RATE_CONVERSION_CONSTANT
+        * 100.0
+    )
     ret['ppa_escalation'] = ppa_escalation_rate_percent
 
     # Debt/equity ratio ('Fraction of Investment in Bonds' parameter)

tests/geophires_x_tests/test_economics_sam.py

@@ -13,7 +13,12 @@
 from geophires_x.Model import Model
 
 # noinspection PyProtectedMember
-from geophires_x.EconomicsSam import calculate_sam_economics, _sig_figs, _SAM_CASH_FLOW_PROFILE_KEY
+from geophires_x.EconomicsSam import (
+    calculate_sam_economics,
+    _sig_figs,
+    _SAM_CASH_FLOW_PROFILE_KEY,
+    _GEOPHIRES_TO_SAM_PRICING_MODEL_RATE_CONVERSION_CONSTANT,
+)
 
 # noinspection PyProtectedMember
 from geophires_x.EconomicsSamCashFlow import _clean_profile
@@ -50,7 +55,19 @@ def _npv(r: GeophiresXResult) -> float:
         self.assertEqual(ir['value'], 7.0)
         self.assertEqual(ir['unit'], '%')
 
-        npvs = [_npv(self._get_result({'Starting Electricity Sale Price': x / 100.0})) for x in range(1, 20, 4)]
+        inflation = 0.02
+        rate_params = [
+            {
+                'Starting Electricity Sale Price': x / 100.0,
+                # Escalation rate must remain constant percent
+                'Electricity Escalation Rate Per Year': x
+                * inflation
+                / 100.0
+                / _GEOPHIRES_TO_SAM_PRICING_MODEL_RATE_CONVERSION_CONSTANT,
+            }
+            for x in range(1, 20, 4)
+        ]
+        npvs = [_npv(self._get_result(rp)) for rp in rate_params]
         for i in range(len(npvs) - 1):
             self.assertLess(npvs[i], npvs[i + 1])