use higher lifetime only for existing German gas CHPs

Author: lindnemi

config/config.de.yaml

@@ -4,7 +4,7 @@
 
 # docs in https://pypsa-eur.readthedocs.io/en/latest/configuration.html#run
 run:
-  prefix: 20250507_simple_scenarios
+  prefix: 20253006_fix_chp_lifetime
   name:
   # - ExPol
   - KN2045_Mix

scripts/add_existing_baseyear.py

@@ -510,6 +510,10 @@ def add_chp_plants(n, grouping_years, costs, baseyear):
     chp["lifetime"] = (chp.DateOut - chp["grouping_year"] + 1).fillna(
         snakemake.params.costs["fill_values"]["lifetime"]
     )
+    chp.loc[chp.Fueltype == "gas", "lifetime"] = (
+        chp.DateOut - chp["grouping_year"] + 1
+    ).fillna(40)
+
     chp = chp.loc[
         chp.grouping_year + chp.lifetime > baseyear
     ]  # in add_brownfield this is build_year + lifetime <= baseyear
@@ -885,12 +889,19 @@ def add_heating_capacities_installed_before_baseyear(
 
             assert valid_grouping_years.is_monotonic_increasing
 
-            # get number of years of each interval
-            _years = valid_grouping_years.diff()
-            # Fill NA from .diff() with value for the first interval
-            _years[0] = valid_grouping_years[0] - baseyear + default_lifetime
-            # Installation is assumed to be linear for the past
-            ratios = _years / _years.sum()
+            if len(valid_grouping_years) == 0:
+                logger.warning(
+                    f"No valid grouping years found for {heat_system}. "
+                    "No existing capacities will be added."
+                )
+                ratios = []
+            else:
+                # get number of years of each interval
+                _years = valid_grouping_years.diff()
+                # Fill NA from .diff() with value for the first interval
+                _years[0] = valid_grouping_years[0] - baseyear + default_lifetime
+                # Installation is assumed to be linear for the past
+                ratios = _years / _years.sum()
 
         for ratio, grouping_year in zip(ratios, valid_grouping_years):
             # Add heat pumps

scripts/pypsa-de/modify_cost_data.py

@@ -140,12 +140,6 @@ def carbon_component_fossils(costs, co2_price):
         f"Scaling central water tank storage investment costs to KEA Technikkatalog: {costs.loc['central water tank storage', 'investment'].value} {costs.loc['central water tank storage', 'investment'].unit}."
     )
 
-    # increase central gas CHP lifetime to 40 years
-    costs.at[("central gas CHP", "lifetime"), "value"] = 40
-    logger.info(
-        f"Setting lifetime of central gas CHP to {costs.at[('central gas CHP', 'lifetime'), 'value']} {costs.at[('central gas CHP', 'lifetime'), 'unit']}."
-    )
-
     # decrease Fischer-Tropsch efficiency
     costs.at[("Fischer-Tropsch", "efficiency"), "value"] = (
         1 / costs.at[("Fischer-Tropsch", "hydrogen-input"), "value"]