migrate co2 budgets feature from pypsa-at

config/config.default.yaml

@@ -1190,6 +1190,7 @@ solving:
     EQ: false
     BAU: false
     SAFE: false
+    co2_budget_national: {}
   solver:
     name: gurobi
     options: "gurobi-default"

config/schema.default.json

@@ -5476,6 +5476,16 @@
               "default": false,
               "description": "Add a capacity reserve margin of a certain fraction above the peak demand to which renewable generators and storage do *not* contribute. Ignores network.",
               "type": "boolean"
+            },
+            "co2_budget_national": {
+              "additionalProperties": {
+                "additionalProperties": {
+                  "type": "number"
+                },
+                "type": "object"
+              },
+              "description": "Per-country CO2 budget constraints for myopic foresight, keyed by two-letter country code and then by planning horizon year. Values are the allowed emissions as a fraction of the country's 1990 emissions (e.g. `0.0` for net-zero, negative for net-negative). Emissions are balanced over all links of a country connecting to the `co2 atmosphere` bus, with aviation scaled by the domestic share. Leave empty to disable.",
+              "type": "object"
             }
           }
         },
@@ -5999,6 +6009,16 @@
           "default": false,
           "description": "Add a capacity reserve margin of a certain fraction above the peak demand to which renewable generators and storage do *not* contribute. Ignores network.",
           "type": "boolean"
+        },
+        "co2_budget_national": {
+          "additionalProperties": {
+            "additionalProperties": {
+              "type": "number"
+            },
+            "type": "object"
+          },
+          "description": "Per-country CO2 budget constraints for myopic foresight, keyed by two-letter country code and then by planning horizon year. Values are the allowed emissions as a fraction of the country's 1990 emissions (e.g. `0.0` for net-zero, negative for net-negative). Emissions are balanced over all links of a country connecting to the `co2 atmosphere` bus, with aviation scaled by the domestic share. Leave empty to disable.",
+          "type": "object"
         }
       }
     },
@@ -12540,6 +12560,16 @@
               "default": false,
               "description": "Add a capacity reserve margin of a certain fraction above the peak demand to which renewable generators and storage do *not* contribute. Ignores network.",
               "type": "boolean"
+            },
+            "co2_budget_national": {
+              "additionalProperties": {
+                "additionalProperties": {
+                  "type": "number"
+                },
+                "type": "object"
+              },
+              "description": "Per-country CO2 budget constraints for myopic foresight, keyed by two-letter country code and then by planning horizon year. Values are the allowed emissions as a fraction of the country's 1990 emissions (e.g. `0.0` for net-zero, negative for net-negative). Emissions are balanced over all links of a country connecting to the `co2 atmosphere` bus, with aviation scaled by the domestic share. Leave empty to disable.",
+              "type": "object"
             }
           }
         },

doc/foresight.rst

@@ -194,6 +194,56 @@ transformations required in Europe to achieve different climate goals (2022)
 <https://doi.org/10.1016/j.joule.2022.04.016>`__.
 
 
+.. _national_co2_budgets:
+
+National CO2 budgets
+--------------------
+
+In addition to the system-wide carbon budget, individual countries can be given
+their own CO2 budget to model differentiated, country-specific climate targets
+(for example, Austria's path to climate neutrality by 2040 following its
+*Klimaschutzgesetz* targets). National budgets are available in myopic foresight
+and are configured under ``solving: constraints: co2_budget_national`` as a
+fraction of each country's 1990 emissions, keyed by country code and planning
+horizon:
+
+.. code:: yaml
+
+  solving:
+    constraints:
+      co2_budget_national:
+        AT:
+          2020: 0.67   # 67% of 1990 emissions
+          2030: 0.34
+          2040: 0.00   # net-zero
+          2050: -0.05  # net-negative
+
+Leave the mapping empty (the default) to disable the feature. The absolute
+1990 reference is taken from ``co2_totals.csv`` for the emission sectors enabled
+in the ``sector`` configuration, scaled to the number of years represented by
+the planning horizon.
+
+For every listed country and planning horizon a constraint is added that
+balances all emissions at the ``co2 atmosphere`` bus:
+
+1. all links of the country connecting to the ``co2 atmosphere`` bus are
+   identified, across all of their bus ports;
+2. emissions (positive and negative) are accounted for in the region where the
+   technology causes them, so emissions in one region of a country can be
+   compensated by negative emissions (CCS, DAC, CCU) in another region of the
+   *same* country;
+3. aviation emissions are scaled by the domestic-to-total aviation ratio
+   (from ``energy_totals.csv``) so that international aviation is excluded;
+4. the resulting sum is constrained to be below the national budget:
+   :math:`\sum \text{emissions} \le \text{budget}_{ct}`.
+
+Unlike the PyPSA-DE implementation this feature is derived from, no distinction
+is made between synthetic and fossil fuels: all emissions are booked where
+combustion occurs, and a country cannot use synthetic-fuel production to offset
+emissions in another country. The constraint can be combined with the global
+``co2limit``/carbon budget, which continues to cap system-wide emissions.
+
+
 General myopic code structure
 ---------------------------------
 

doc/release_notes.rst

@@ -9,6 +9,8 @@ Release Notes
 .. Upcoming Release
 .. =================
 
+* feat: Add optional per-country CO2 budget constraints for myopic foresight, configurable via ``solving: constraints: co2_budget_national`` as a fraction of each country's 1990 emissions per planning horizon. Emissions are balanced at the ``co2 atmosphere`` bus per country, with aviation scaled by the domestic share. See :ref:`national_co2_budgets`.
+
 * Fix: ``atlite.plot_availability_matrix`` config option for :mod:`determine_availability_matrix` and :mod:`determine_availability_matrix_MD_UA` scripts, changed their output and behaviour to align consistently (https://github.com/PyPSA/pypsa-eur/pull/2173).
 
 * Fix: Activate losses for `H2 pipeline retrofitted` links by default, to ensure consistency with `H2 pipeline` links.

rules/solve_myopic.smk

@@ -109,6 +109,8 @@ rule solve_sector_network_myopic:
         network=resources(
             "networks/base_s_{clusters}_{opts}_{sector_opts}_{planning_horizons}_brownfield.nc"
         ),
+        co2_totals=resources("co2_totals.csv"),
+        energy_totals=resources("energy_totals.csv"),
     output:
         network=RESULTS
         + "networks/base_s_{clusters}_{opts}_{sector_opts}_{planning_horizons}.nc",
@@ -144,6 +146,7 @@ rule solve_sector_network_myopic:
         co2_sequestration_potential=config_provider(
             "sector", "co2_sequestration_potential", default=200
         ),
+        energy_totals_year=config_provider("energy", "energy_totals_year"),
         custom_extra_functionality=input_custom_extra_functionality,
     message:
         "Solving sector-coupled network with myopic foresight for {wildcards.clusters} clusters, {wildcards.planning_horizons} planning horizons, {wildcards.opts} electric options and {wildcards.sector_opts} sector options"

scripts/lib/validation/config/solving.py

@@ -245,6 +245,10 @@ class _ConstraintsConfig(BaseModel):
         False,
         description="Add a capacity reserve margin of a certain fraction above the peak demand to which renewable generators and storage do *not* contribute. Ignores network.",
     )
+    co2_budget_national: dict[str, dict[int, float]] = Field(
+        default_factory=dict,
+        description="Per-country CO2 budget constraints for myopic foresight, keyed by two-letter country code and then by planning horizon year. Values are the allowed emissions as a fraction of the country's 1990 emissions (e.g. `0.0` for net-zero, negative for net-negative). Emissions are balanced over all links of a country connecting to the `co2 atmosphere` bus, with aviation scaled by the domestic share. Leave empty to disable.",
+    )
 
 
 class _SolverConfig(BaseModel):

scripts/solve_network.py

@@ -1220,6 +1220,147 @@ def add_co2_atmosphere_constraint(n, snapshots):
             n.model.add_constraints(lhs <= rhs, name=f"GlobalConstraint-{name}")
 
 
+def add_national_co2_budget_constraints(
+    n: pypsa.Network,
+    planning_horizons: str,
+    snakemake,
+) -> None:
+    """
+    Add per-country CO2 budget constraints based on a balance at the
+    ``co2 atmosphere`` bus.
+
+    Budgets are configured per country and planning horizon under
+    ``solving: constraints: co2_budget_national`` as a fraction of the
+    country's 1990 emissions. Emissions (positive and negative) are
+    balanced over all links of a country that connect to the
+    ``co2 atmosphere`` bus, so that emissions are accounted for in the
+    region where they occur. Whether fossil or synthetic fuels are burned
+    makes no difference; all emissions are booked where combustion occurs.
+    Aviation kerosene emissions are scaled by the domestic-to-total
+    aviation ratio to exclude international aviation from the budget.
+    """
+    from scripts.prepare_sector_network import determine_emission_sectors
+
+    national_co2_budgets = snakemake.config["solving"]["constraints"][
+        "co2_budget_national"
+    ]
+    investment_year = int(planning_horizons)
+
+    logger.info(f"Adding national CO2 budgets for year {investment_year}")
+
+    nyears = n.snapshot_weightings.generators.sum() / 8760
+    MtCO2_to_tCO2 = 1e6
+
+    co2_totals = pd.read_csv(snakemake.input.co2_totals, index_col=0).mul(MtCO2_to_tCO2)
+    sectors = determine_emission_sectors(n.config["sector"])
+    co2_sector = co2_totals[sectors].sum(axis=1) * nyears
+
+    energy_totals = pd.read_csv(snakemake.input.energy_totals, index_col=[0, 1])
+    energy_year = int(snakemake.params.energy_totals_year)
+
+    weightings = n.snapshot_weightings.generators
+    links = n.links
+
+    for ct, yearly_percent in national_co2_budgets.items():
+        if investment_year in yearly_percent:
+            continue
+
+        percent = yearly_percent[investment_year]
+        budget = co2_sector[ct] * percent
+        logger.info(
+            f"Limiting emissions in country {ct} to "
+            f"{percent:.1%} of 1990 levels, "
+            f"i.e. {budget:,.2f} tCO2/a"
+        )
+
+        lhs = []
+        link_ports = links.filter(like="bus").columns.str[3:]
+        for port in link_ports:
+            # aviation is excluded here to scale it by the domestic share below
+            idx = links.query(
+                f"name.str.startswith('{ct}') "
+                f"& bus{port} == 'co2 atmosphere' "
+                f"& carrier != 'kerosene for aviation'"
+            ).index
+
+            if idx.empty:
+                continue
+
+            logger.info(
+                f"For {ct} adding the following link carriers on port {port} "
+                f"to the CO2 constraint: {sorted(links.loc[idx, 'carrier'].unique())}"
+            )
+
+            if port == "0":
+                efficiency = -1.0
+            elif port == "1":
+                efficiency = links.loc[idx, "efficiency"]
+            else:
+                efficiency = links.loc[idx, f"efficiency{port}"]
+
+            port_emissions = (
+                n.model["Link-p"].loc[:, idx].mul(efficiency).mul(weightings).sum()
+            )
+            lhs.append(port_emissions)
+
+        # Scale aviation emissions by the domestic share to exclude
+        # international aviation from the national budget.
+        aviation_domestic = energy_totals.loc[
+            (ct, energy_year), "total domestic aviation"
+        ]
+        aviation_international = energy_totals.loc[
+            (ct, energy_year), "total international aviation"
+        ]
+        aviation_total = aviation_domestic + aviation_international
+        domestic_aviation_factor = (
+            aviation_domestic / aviation_total if aviation_total else 0.0
+        )
+        aviation_links = links.query(
+            f"name.str.startswith('{ct}') & carrier == 'kerosene for aviation'"
+        )
+        if not aviation_links.empty:
+            aviation_emissions = (
+                n.model["Link-p"]
+                .loc[:, aviation_links.index]
+                # 'co2 atmosphere' is assumed to be at bus2 for aviation links
+                .mul(aviation_links["efficiency2"])
+                .mul(weightings)
+                .sum()
+                .mul(domestic_aviation_factor)
+            )
+            lhs.append(aviation_emissions)
+            logger.info(
+                f"Adding domestic aviation emissions for {ct} with a "
+                f"factor of {domestic_aviation_factor:.2f}"
+            )
+
+        if not lhs:
+            logger.warning(
+                f"No links connecting to 'co2 atmosphere' found for {ct}; "
+                "skipping its national CO2 budget constraint."
+            )
+            continue
+
+        cname = f"co2_limit-{ct}"
+
+        n.model.add_constraints(sum(lhs) <= budget, name=f"GlobalConstraint-{cname}")
+
+        if cname in n.global_constraints.index:
+            logger.warning(
+                f"Global constraint {cname} already exists. Dropping and re-adding it."
+            )
+            n.global_constraints.drop(cname, inplace=True)
+
+        n.add(
+            "GlobalConstraint",
+            cname,
+            constant=budget,
+            sense="<=",
+            type="",
+            carrier_attribute="",
+        )
+
+
 def extra_functionality(
     n: pypsa.Network, snapshots: pd.DatetimeIndex, planning_horizons: str | None = None
 ) -> None:
@@ -1283,6 +1424,8 @@ def extra_functionality(
         add_retrofit_gas_boiler_constraint(n, snapshots)
     else:
         add_co2_atmosphere_constraint(n, snapshots)
+        if constraints.get("co2_budget_national") and planning_horizons is not None:
+            add_national_co2_budget_constraints(n, planning_horizons, snakemake)  # pylint: disable=E0601
 
     if config["sector"]["enhanced_geothermal"]["enable"]:
         add_flexible_egs_constraint(n)