link losses: exponential rather than linear model

config/config.default.yaml

@@ -478,11 +478,14 @@ sector:
   electricity_distribution_grid: true
   electricity_distribution_grid_cost_factor: 1.0
   electricity_grid_connection: true
-  transmission_losses:
-    # per 1000 km
-    DC: 0
-    H2 pipeline: 0
-    gas pipeline: 0
+  transmission_efficiency:
+    DC:
+      efficiency_static: 0.98
+      efficiency_per_1000km: 0.977
+    H2 pipeline:
+      efficiency_per_1000km: 0.979
+    gas pipeline:
+      efficiency_per_1000km: 0.977
   H2_network: true
   gas_network: false
   H2_retrofit: false

scripts/prepare_sector_network.py

@@ -3280,22 +3280,27 @@ def set_temporal_aggregation(n, opts, solver_name):
     return n
 
 
-def lossy_bidirectional_links(n, carrier, losses_per_thousand_km=0.0):
+def lossy_bidirectional_links(n, carrier, efficiencies={}):
     "Split bidirectional links into two unidirectional links to include transmission losses."
 
     carrier_i = n.links.query("carrier == @carrier").index
 
-    if not losses_per_thousand_km or carrier_i.empty:
+    if not any(v != 1. for v in efficiencies.values()) or carrier_i.empty:
         return
 
+    efficiency_static = efficiencies.get("efficiency_static", 1)
+    efficiency_per_1000km = efficiencies.get("efficiency_per_1000km", 1)
+
     logger.info(
-        f"Specified losses for {carrier} transmission. Splitting bidirectional links."
+        f"Specified losses for {carrier} transmission"
+        f"(static: {efficiency_static}, per 1000km: {efficiency_per_1000km})."
+        "Splitting bidirectional links."
     )
 
     carrier_i = n.links.query("carrier == @carrier").index
     n.links.loc[carrier_i, "p_min_pu"] = 0
     n.links.loc[carrier_i, "efficiency"] = (
-        1 - n.links.loc[carrier_i, "length"] * losses_per_thousand_km / 1e3
+        efficiency_static * efficiency_per_1000km ** (n.links.loc[carrier_i, "length"] / 1e3)
     )
     rev_links = (
         n.links.loc[carrier_i].copy().rename({"bus0": "bus1", "bus1": "bus0"}, axis=1)
@@ -3474,7 +3479,7 @@ if __name__ == "__main__":
     if options["electricity_grid_connection"]:
         add_electricity_grid_connection(n, costs)
 
-    for k, v in options["transmission_losses"].items():
+    for k, v in options["transmission_efficiency"].items():
         lossy_bidirectional_links(n, k, v)
 
     # Workaround: Remove lines with conflicting (and unrealistic) properties