fix: split cost + length for multi-link projects (#793)

* fix: split cost + length for multi-link projects

* refactor: rename to investment_attrs_per_line

* refactor: move cost + lengt split into an extra fct

* docs: add release note

* fix: align docstring

Co-authored-by: Daniel Rüdt <117752024+daniel-rdt@users.noreply.github.com>

---------

Co-authored-by: Daniel Rüdt <117752024+daniel-rdt@users.noreply.github.com>

Author: lisazeyen

doc/release_notes.md

@@ -37,6 +37,8 @@
 
 **Bugfixes and Compatibility**
 
+* Fix: split project-level cost and length evenly across lines for multi-link transmission projects, avoiding inflated values ([#793](https://github.com/open-energy-transition/open-tyndp/pull/793)).
+
 * Use `overnight` foresight in MSV network preparation instead of `perfect` ([#813](https://github.com/open-energy-transition/open-tyndp/pull/813)).
 
 * Rename bus for `t339` project (Tyrrhenian) from ITSI to ITVI ([#751](https://github.com/open-energy-transition/open-tyndp/pull/751)).
@@ -93,9 +95,13 @@
 ## Upcoming PyPSA-Eur Release
 
 * fix: update stale contribution docs (linting and formatting ruff)
+
 * feat: data version CSV / YAML file can be specified separately or extended by the user in the `data.version_files` config entry ([#2016](https://github.com/PyPSA/pypsa-eur/issues/2016)).
+
 * Fix: Resolve plotting crashes from missing `tech_colors` entries by adding `heat dsm` color and implementing upfront validation for missing keys in `plot_summary.py` ([#2108](https://github.com/PyPSA/pypsa-eur/issues/2108)).
+
 * Fix: Retry interrupted WDPA and WDPA-marine downloads ([#2138](https://github.com/PyPSA/pypsa-eur/issues/2138)).
+
 * feat: Make the default target rule configurable (defaults to "all" for backwards compatibility)
 
 * Fix: Keep unset `p_set` (NaN) as NaN when aggregating components in `cluster_heat_buses`, required for [PyPSA#1703](https://github.com/PyPSA/PyPSA/pull/1703).

scripts/cba/clean_projects.py

@@ -65,36 +65,6 @@
 }
 
 
-def read_tyndp_electricity_buses(buses_fn: str) -> pd.Index:
-    """
-    Read the list of electricity nodes from the TYNDP input data.
-
-    Parameters
-    ----------
-    buses_fn : str
-        Path to the list of nodes from the TYNDP bundle.
-
-    Returns
-    -------
-    pd.Index
-        Electricity buses as used in Open-TYNDP.
-
-    See Also
-    --------
-    build_tyndp_network.build_buses
-    """
-    buses = pd.Index(
-        pd.read_excel(buses_fn)
-        .replace("UK", "GB", regex=True)
-        .rename({"NODE": "bus_id"}, axis=1)["bus_id"]
-    )
-
-    # Manually add Italian virtual nodes
-    buses = buses.union(["ITCO", "ITVI"])
-
-    return buses
-
-
 def extract_transmission_projects(
     excel_path: Path, existing_buses: pd.Index
 ) -> pd.DataFrame:
@@ -343,6 +313,64 @@ def build_method_assignments(
     return projects.merge(assigned, on="project_id", how="left")
 
 
+def read_tyndp_electricity_buses(buses_fn: str):
+    """
+    Read node list for electricity from tyndp data input.
+
+    Parameters
+    ----------
+        - buses_fn (str): Path to "LIST OF NODES.xlsx" from tyndp bundle
+
+    Returns
+    -------
+        - buses: Index of electricity buses as used in Open-TYNDP
+
+    See Also
+    --------
+        build_tyndp_network.py : build_buses
+    """
+    buses = pd.Index(
+        pd.read_excel(buses_fn)
+        .replace("UK", "GB", regex=True)
+        .rename({"NODE": "bus_id"}, axis=1)["bus_id"]
+    )
+
+    # Manually add Italian virtual nodes
+    buses = buses.union(["ITCO", "ITVI"])
+
+    return buses
+
+
+def split_investment_attributes_per_line(
+    investment_attrs: pd.DataFrame, transmission_projects: pd.DataFrame
+) -> pd.DataFrame:
+    """
+    Split investment costs and length evenly across transmission lines.
+
+    Investment costs and length are given per project and not per
+    transmission line, therefore these attributes need to be split before
+    merging.
+
+    Parameters
+    ----------
+    investment_attrs : pd.DataFrame
+        Investment attributes indexed by project_id.
+    transmission_projects : pd.DataFrame
+        Transmission projects with a project_id column.
+
+    Returns
+    -------
+    pd.DataFrame
+        investment_attrs with length_km and capex_meur divided by the number
+        of lines per project.
+    """
+    link_counts = transmission_projects.groupby("project_id").size()
+    return investment_attrs.assign(
+        length_km=lambda d: d.length_km / d.index.map(link_counts).fillna(1),
+        capex_meur=lambda d: d.capex_meur / d.index.map(link_counts).fillna(1),
+    )
+
+
 if __name__ == "__main__":
     if "snakemake" not in globals():
         from scripts._helpers import mock_snakemake
@@ -361,8 +389,13 @@ def build_method_assignments(
     transmission_projects = extract_transmission_projects(excel_path, existing_buses)
 
     investment_attrs = extract_investment_attributes(excel_path)
+
+    investment_attrs_per_line = split_investment_attributes_per_line(
+        investment_attrs, transmission_projects
+    )
+
     transmission_projects = transmission_projects.merge(
-        investment_attrs, on="project_id", how="left"
+        investment_attrs_per_line, on="project_id", how="left"
     )
 
     transmission_projects.to_csv(snakemake.output.transmission_projects, index=False)