Fix calculation of solar rooftop potentials for "m" clusters

I.e. when the generators are clustered to the "simplified" network
resolution, but the grid is clustered further, e.g. by using the
clusters = 37m "m" option.

Snakefile

@@ -62,6 +62,18 @@ rule build_clustered_population_layouts:
     script: "scripts/build_clustered_population_layouts.py"
 
 
+rule build_simplified_population_layouts:
+    input:
+        pop_layout_total="resources/pop_layout_total.nc",
+        pop_layout_urban="resources/pop_layout_urban.nc",
+        pop_layout_rural="resources/pop_layout_rural.nc",
+        regions_onshore=pypsaeur('resources/regions_onshore_{network}_s{simpl}.geojson')
+    output:
+        clustered_pop_layout="resources/pop_layout_{network}_s{simpl}.csv"
+    resources: mem_mb=10000
+    script: "scripts/build_clustered_population_layouts.py"
+
+
 rule build_heat_demands:
     input:
         pop_layout_total="resources/pop_layout_total.nc",
@@ -235,6 +247,7 @@ rule prepare_sector_network:
         profile_offwind_dc=pypsaeur("resources/profile_offwind-dc.nc"),
         clustermaps=pypsaeur('resources/clustermaps_{network}_s{simpl}_{clusters}.h5'),
         clustered_pop_layout="resources/pop_layout_{network}_s{simpl}_{clusters}.csv",
+        simplified_pop_layout="resources/pop_layout_{network}_s{simpl}.csv",
         industrial_demand="resources/industrial_demand_{network}_s{simpl}_{clusters}.csv",
         heat_demand_urban="resources/heat_demand_urban_{network}_s{simpl}_{clusters}.nc",
         heat_demand_rural="resources/heat_demand_rural_{network}_s{simpl}_{clusters}.nc",

scripts/prepare_sector_network.py

@@ -689,8 +689,14 @@ def insert_electricity_distribution_grid(network):
     solar = network.generators.index[network.generators.carrier == "solar"]
     network.generators.loc[solar, "capital_cost"] = costs.at['solar-utility',
                                                              'fixed']
-    # add max solar rooftop potential assuming 1kW/person
-    potential = pop_layout.total.rename(index = lambda x: x + " solar")
+    if snakemake.wildcards.clusters[-1:] == "m":
+        pop_solar = simplified_pop_layout.total.rename(index = lambda x: x + " solar")
+    else:
+        pop_solar = pop_layout.total.rename(index = lambda x: x + " solar")
+
+    # add max solar rooftop potential assuming 0.1 kW/m2 and 10 m2/person,
+    #i.e. 1 kW/person (population data is in thousands of people) so we get MW
+    potential = 0.1*10*pop_solar
 
     network.madd("Generator",
                  solar,
@@ -1778,6 +1784,8 @@ def remove_h2_network(n):
     pop_layout["ct_total"] = pop_layout["ct"].map(ct_total.get)
     pop_layout["fraction"] = pop_layout["total"]/pop_layout["ct_total"]
 
+    simplified_pop_layout = pd.read_csv(snakemake.input.simplified_pop_layout,index_col=0)
+
     costs = prepare_costs(snakemake.input.costs,
                           snakemake.config['costs']['USD2013_to_EUR2013'],
                           snakemake.config['costs']['discountrate'],