allow H2 retrofitting from CH4 pipelines without endogenous CH4 grid (#204)

* allow H2 retrofitting from CH4 pipelines without endogenous CH4 grid

* add small capital cost to gas pipelines to incentivise decommissioning

* add release notes

Snakefile

@@ -101,7 +101,7 @@ rule build_simplified_population_layouts:
     script: "scripts/build_clustered_population_layouts.py"
 
 
-if config["sector"]["gas_network"]:
+if config["sector"]["gas_network"] or config["sector"]["H2_retrofit"]:
 
     datafiles = [
         "IGGIELGN_LNGs.geojson",

config.default.yaml

@@ -256,7 +256,7 @@ sector:
   # https://gasforclimate2050.eu/wp-content/uploads/2020/07/2020_European-Hydrogen-Backbone_Report.pdf
   # 60% of original natural gas capacity could be used in cost-optimal case as H2 capacity
   H2_retrofit_capacity_per_CH4: 0.6  # ratio for H2 capacity per original CH4 capacity of retrofitted pipelines
-  gas_network_connectivity_upgrade: 3 # https://networkx.org/documentation/stable/reference/algorithms/generated/networkx.algorithms.connectivity.edge_augmentation.k_edge_augmentation.html#networkx.algorithms.connectivity.edge_augmentation.k_edge_augmentation
+  gas_network_connectivity_upgrade: 1 # https://networkx.org/documentation/stable/reference/algorithms/generated/networkx.algorithms.connectivity.edge_augmentation.k_edge_augmentation.html#networkx.algorithms.connectivity.edge_augmentation.k_edge_augmentation
   gas_distribution_grid: true
   gas_distribution_grid_cost_factor: 1.0  #multiplies cost in data/costs.csv
   biomass_transport: false  # biomass transport between nodes

doc/release_notes.rst

@@ -41,13 +41,14 @@ incorporates retrofitting options to hydrogen.
   the gas network is activated, all the gas demands are regionally disaggregated
   as well.
 
-* New constraint allows retrofitting of gas pipelines to hydrogen pipelines.
+* New constraint allows endogenous retrofitting of gas pipelines to hydrogen pipelines.
   This option is activated via the setting ``sector: H2_retrofit:``. For every
   unit of gas pipeline capacity dismantled, ``sector:
   H2_retrofit_capacity_per_CH4`` units are made available as hydrogen pipeline
   capacity in the corresponding corridor. These repurposed hydrogen pipelines
   have lower costs than new hydrogen pipelines. Both new and repurposed pipelines
-  can be built simultaneously.
+  can be built simultaneously. The retrofitting option ``sector: H2_retrofit:`` also works 
+  with a copperplated methane infrastructure, i.e. when ``sector: gas_network: false``. 
 
 * New hydrogen pipelines can now be built where there are already power or gas
   transmission routes. Previously, only the electricity transmission routes were

scripts/prepare_sector_network.py

@@ -1078,17 +1078,20 @@ def add_storage_and_grids(n, costs):
         capital_cost=h2_capital_cost
     )
 
-    if options["gas_network"]:
-
-        logger.info("Add gas network")
+    if options["gas_network"] or options["H2_retrofit"]:
 
         fn = snakemake.input.clustered_gas_network
         gas_pipes = pd.read_csv(fn, index_col=0)
 
+    if options["gas_network"]:
+
+        logger.info("Add gas infrastructure, incl. LNG terminals, production and entry-points.")
+
         if options["H2_retrofit"]:
             gas_pipes["p_nom_max"] = gas_pipes.p_nom
             gas_pipes["p_nom_min"] = 0.
-            gas_pipes["capital_cost"] = 0.
+            # 0.1 EUR/MWkm/a to prefer decommissioning to address degeneracy
+            gas_pipes["capital_cost"] = 0.1 * gas_pipes.length
         else:
             gas_pipes["p_nom_max"] = np.inf
             gas_pipes["p_nom_min"] = gas_pipes.p_nom
@@ -1163,13 +1166,13 @@ def add_storage_and_grids(n, costs):
             lifetime=costs.at['CH4 (g) pipeline', 'lifetime']
         )
 
-    # retroftting existing CH4 pipes to H2 pipes
-    if options["gas_network"] and options["H2_retrofit"]:
+    if options["H2_retrofit"]:
 
-        gas_pipe_i = n.links[n.links.carrier == "gas pipeline"].index
-        n.links.loc[gas_pipe_i, "p_nom_extendable"] = True
-        h2_pipes = gas_pipes.rename(index=lambda x:
-                                    x.replace("gas pipeline", "H2 pipeline retrofitted"))
+        logger.info("Add retrofitting options of existing CH4 pipes to H2 pipes.")
+
+        fr = "gas pipeline"
+        to = "H2 pipeline retrofitted"
+        h2_pipes = gas_pipes.rename(index=lambda x: x.replace(fr, to))
 
         n.madd("Link",
             h2_pipes.index,
@@ -1187,6 +1190,8 @@ def add_storage_and_grids(n, costs):
 
     if options.get("H2_network", True):
 
+        logger.info("Add options for new hydrogen pipelines.")
+
         h2_pipes = create_network_topology(n, "H2 pipeline ", carriers=["DC", "gas pipeline"])
 
         # TODO Add efficiency losses

scripts/solve_network.py

@@ -200,8 +200,10 @@ def add_pipe_retrofit_constraint(n):
 
     CH4_per_H2 = 1 / n.config["sector"]["H2_retrofit_capacity_per_CH4"]
 
+    fr = "H2 pipeline retrofitted"
+    to = "gas pipeline"
     lhs = linexpr(
-        (CH4_per_H2, link_p_nom.loc[h2_retrofitted_i].rename(index=lambda x: x.replace("H2 pipeline retrofitted", "gas pipeline"))),
+        (CH4_per_H2, link_p_nom.loc[h2_retrofitted_i].rename(index=lambda x: x.replace(fr, to))),
         (1, link_p_nom.loc[gas_pipes_i])
     )