Add optional emission buses to facades

src/oemof/tabular/facades/conversion.py

@@ -105,6 +105,8 @@ class Conversion(Converter, Facade):
 
     output_parameters: dict = field(default_factory=dict)
 
+    emissions: dict = field(default_factory=dict)
+
     def build_solph_components(self):
         """ """
         self.conversion_factors.update(
@@ -132,3 +134,12 @@ def build_solph_components(self):
                 )
             }
         )
+
+        if self.emissions:
+            self.outputs.update({bus: Flow() for bus in self.emissions.keys()})
+            self.conversion_factors.update(
+                {
+                    bus: sequence(emission_factor)
+                    for bus, emission_factor in self.emissions.items()
+                }
+            )

tests/test_constraints.py

@@ -323,13 +323,16 @@ def test_conversion(self):
         r""" """
         bus_biomass = solph.Bus("biomass")
         bus_heat = solph.Bus("heat")
+        bus_co2_em = solph.Bus("co2_em")
+        bus_ch4_em = solph.Bus("ch4_em")
 
         conversion = Conversion(
             label="biomass_plant",
             carrier="biomass",
             tech="st",
             from_bus=bus_biomass,
             to_bus=bus_heat,
+            emissions={bus_co2_em: 0.5, bus_ch4_em: 10},
             capacity=100,
             efficiency=0.4,
         )