fix: Avoid duplication of regional co2 sequestration potential in myopic optimization

doc/design/carbon-management.md

@@ -86,6 +86,10 @@ years. Storage sites can be resolved regionally from a geological database
 of potentials, with a choice between offshore formations only, which are
 larger and far from settlements, and onshore formations as well.
 
+Regional geological potentials are divided by `years_of_storage` to obtain
+the modeled annual potential. A fixed-capacity, negative-dispatch Generator
+enforces each region's potential and charges the sequestration cost.
+
 !!! warning "The sequestration limit shapes the result"
     The limit is a deliberate choice: it keeps sequestration for
     hard-to-abate emissions and prevents it from becoming a backstop that

doc/release_notes.md

@@ -6,8 +6,12 @@
 <!-- Upcoming Release -->
 <!-- ================= -->
 
+
+* Fix: Regional CO2 sequestration allowances no longer accumulate across myopic planning horizons. Sequestration Stores are replaced by fixed-capacity Generators with energy-sum limits and infinite lifetimes, preventing brownfield carry-over from duplicating regional potentials. Sequestration costs are charged on Generator dispatch instead of the connecting Links. This can change sequestration locations and CO2 pipeline expansion ([#2369](https://github.com/PyPSA/pypsa-eur/pull/2369), fixes [#2368](https://github.com/PyPSA/pypsa-eur/issues/2368)).
+
 * Fix: `lines: types` must now define a line type for the 380 kV level; the config validation fails early with a clear message instead of the workflow failing later ([#2166](https://github.com/PyPSA/pypsa-eur/issues/2166)).
 
+
 * Feature: New switches `industry: solid_biomass_for_industry_cc`, `industry: gas_for_industry_cc` and `industry: process_emissions_cc` to disable the carbon capture options for solid biomass for industry, gas for industry and industrial process emissions. All default to `true`, which matches the previous behaviour ([#2357](https://github.com/PyPSA/pypsa-eur/pull/2357)).
 
 * Feature: New option `sector: electrolysis` to allow hydrogen electrolysis to be configurable ([#2358](https://github.com/PyPSA/pypsa-eur/pull/2358)).

scripts/prepare_sector_network.py

@@ -660,31 +660,6 @@ def add_co2_tracking(
             carrier="co2 expansion",
             unit="t_co2",
         )
-        n.add(
-            "Link",
-            sequestration_buses,
-            bus0=spatial.co2.dense,
-            bus1=sequestration_buses,
-            carrier="co2 sequestered",
-            marginal_cost=options["co2_sequestration_cost"],
-            efficiency=1.0,
-            p_nom=np.inf,
-            p_nom_extendable=False,
-        )
-
-    else:
-        n.add(
-            "Link",
-            sequestration_buses,
-            bus0=spatial.co2.nodes,
-            bus1=sequestration_buses,
-            carrier="co2 sequestered",
-            marginal_cost=options["co2_sequestration_cost"],
-            efficiency=1.0,
-            p_nom=np.inf,
-            p_nom_extendable=False,
-        )
-
     if options["regional_co2_sequestration_potential"]["enable"]:
         if sequestration_potential_file is None:
             raise ValueError(
@@ -713,14 +688,33 @@ def add_co2_tracking(
     else:
         e_nom_max = np.inf
 
+    p_nom = (
+        e_nom_max if options["regional_co2_sequestration_potential"]["enable"] else 1e7
+    )
     n.add(
-        "Store",
+        "Link",
+        sequestration_buses,
+        bus0=spatial.co2.dense if co2_liquefaction else spatial.co2.nodes,
+        bus1=sequestration_buses,
+        carrier="co2 sequestered",
+        efficiency=1.0,
+        p_nom=p_nom,
+        p_nom_extendable=False,
+        lifetime=np.inf,
+    )
+
+    n.add(
+        "Generator",
         sequestration_buses,
-        e_nom_extendable=True,
-        e_nom_max=e_nom_max,
-        marginal_cost=-0.1,
         bus=sequestration_buses,
-        lifetime=options["co2_sequestration_lifetime"],
+        p_nom=p_nom,
+        p_nom_extendable=False,
+        p_min_pu=-1.0,
+        p_max_pu=0,
+        e_sum_min=-e_nom_max,
+        e_sum_max=0,
+        marginal_cost=-options["co2_sequestration_cost"],
+        lifetime=np.inf,  # Lifetime inf means assets from previous horizons get dropped in add_brownfield
         carrier="co2 sequestered",
     )
 

scripts/solve_network.py

@@ -554,7 +554,7 @@ def prepare_network(
         if limit_max_growth is not None and limit_max_growth["enable"]:
             add_max_growth(n, limit_max_growth)
 
-    if n.stores.carrier.eq("co2 sequestered").any():
+    if n.generators.carrier.eq("co2 sequestered").any():
         limit_dict = co2_sequestration_potential
         add_co2_sequestration_limit(
             n, limit_dict=limit_dict, planning_horizons=planning_horizons