fix emission prices (#171)

* fix emission prices

I'm not sure if the previous setup was intentional, but regarding that different generators might have different efficiencies and the emissions are carrier specific only, it makes more sense set net emission price.

* small fix

* update release_notes and config

config.default.yaml

@@ -179,7 +179,7 @@ costs:
     hydro: 0.
     H2: 0.
     battery: 0.
-  emission_prices: # only used with the option Ep
+  emission_prices: # in currency per tonne emission, only used with the option Ep
     co2: 0.
 
 solving:

config.tutorial.yaml

@@ -156,7 +156,7 @@ costs:
     offwind: 0.015
     H2: 0.
     battery: 0.
-  emission_prices: # only used with the option Ep
+  emission_prices: # in currency per tonne emission, only used with the option Ep
     co2: 0.
 
 solving:

doc/release_notes.rst

@@ -21,6 +21,8 @@ Upcoming Release
 
 * Added Google Cloud Platform tutorial (for Windows users).
 
+* Corrected setting of exogenous emission price (in config -> cost -> emission price). This was not weighted by the efficiency and effective emission of the generators. Fixed in `#171 <https://github.com/PyPSA/pypsa-eur/pull/171>`_.
+
 
 PyPSA-Eur 0.2.0 (8th June 2020)
 ==================================

scripts/prepare_network.py

@@ -7,7 +7,7 @@
 Prepare PyPSA network for solving according to :ref:`opts` and :ref:`ll`, such as
 
 - adding an annual **limit** of carbon-dioxide emissions,
-- adding an exogenous **price** of carbon-dioxide emissions (or other kinds),
+- adding an exogenous **price** per tonne emissions of carbon-dioxide (or other kinds),
 - setting an **N-1 security margin** factor for transmission line capacities,
 - specifying a limit on the **cost** of transmission expansion,
 - specifying a limit on the **volume** of transmission expansion, and
@@ -85,8 +85,10 @@ def add_emission_prices(n, emission_prices=None, exclude_co2=False):
     if exclude_co2: emission_prices.pop('co2')
     ep = (pd.Series(emission_prices).rename(lambda x: x+'_emissions') *
           n.carriers.filter(like='_emissions')).sum(axis=1)
-    n.generators['marginal_cost'] += n.generators.carrier.map(ep)
-    n.storage_units['marginal_cost'] += n.storage_units.carrier.map(ep)
+    gen_ep = n.generators.carrier.map(ep) / n.generators.efficiency
+    n.generators['marginal_cost'] += gen_ep
+    su_ep = n.storage_units.carrier.map(ep) / n.storage_units.efficiency_dispatch
+    n.storage_units['marginal_cost'] += su_ep
 
 def set_line_s_max_pu(n):
     # set n-1 security margin to 0.5 for 37 clusters and to 0.7 from 200 clusters