Raise error when using relative deployment algo without flow_cap_max

Author: brynpickering

src/calliope/model.py

@@ -674,10 +674,15 @@ def _score_integer() -> xr.DataArray:
 
         def _score_relative_deployment() -> xr.DataArray:
             """Relative deployment scoring algorithm."""
-            previous_cap = latest_results["flow_cap"].where(spores_techs)
-            relative_cap = previous_cap / self.inputs["flow_cap_max"].where(
-                spores_techs
-            )
+            previous_cap = latest_results["flow_cap"]
+            if (
+                "flow_cap_max" not in self.inputs
+                or (self.inputs["flow_cap_max"].where(spores_techs) == np.inf).any()
+            ):
+                raise exceptions.BackendError(
+                    "Cannot score SPORES with `relative_deployment` when `flow_cap_max` is undefined for some or all tracked technologies."
+                )
+            relative_cap = previous_cap / self.inputs["flow_cap_max"]
 
             new_score = (
                 # Make sure that penalties are applied only to non-negligible relative capacities

tests/test_core_model.py

@@ -1,6 +1,7 @@
 import logging
 from contextlib import contextmanager
 
+import numpy as np
 import numpy.testing
 import pandas as pd
 import pytest
@@ -376,6 +377,20 @@ def test_save_per_spore_skip_cost_op(
             model_baseline_solved_separately._model_data.flow_cap
         )
 
+    def test_spores_relative_deployment_needs_max_param(self):
+        """Can only run the `relative_deployment` algorithm if all techs have flow_cap_max."""
+        model = build_model(
+            {"techs.test_supply_elec.flow_cap_max": np.inf},
+            "spores,spores_tech_tracking,investment_costs",
+        )
+        model.build(mode="spores")
+
+        with pytest.raises(
+            calliope.exceptions.BackendError,
+            match="Cannot score SPORES with `relative_deployment`",
+        ):
+            model.solve(**{"spores.scoring_algorithm": "relative_deployment"})
+
 
 class TestBuild:
     @pytest.fixture