add limitations and result sample

doc/index.rst

@@ -87,6 +87,7 @@ Documentation
 **References**
    
 * :doc:`release_notes`
+* :doc:`limitations`
 * :doc:`contributing`
 
 .. toctree::
@@ -95,8 +96,20 @@ Documentation
    :caption: References
 
    release_notes
+   limitations
    contributing
 
+Learning Energy System Modelling
+================================
+
+If you are (relatively) new to energy system modelling and optimisation
+and plan to use PyPSA-Eur, the following resources are *one way* to get started
+in addition to reading this documentation.
+
+- Documentation of `PyPSA <https://pypsa.readthedocs.io>`_, the package for
+  simulating and optimising modern power systems which PyPSA-Eur uses under the hood.
+- Course on `Energy System Modelling <https://nworbmot.org/courses/esm-2019/>`_,
+  Karlsruhe Institute of Technology (KIT), `Dr. Tom Brown <https://nworbmot.org>`_
 
 Citing PyPSA-Eur
 ================

doc/limitations.rst

@@ -0,0 +1,53 @@
+##########################################
+Limitations
+##########################################
+
+
+While the benefit of an openly available, functional and partially validated
+model of the European transmission system is high, many approximations have
+been made due to missing data.
+The limitations of the dataset are listed below,
+both as a warning to the user and as an encouragement to assist in
+improving the approximations.
+
+- **Network topology:**
+  The grid data is based on a map of the ENTSO-E area that is known
+  to contain small distortions to improve readability. Since the exact impedances
+  of the lines are unknown, approximations based on line lengths and standard
+  line parameters were made that ignore specific conductoring choices for
+  particular lines. There is no openly available data on busbar configurations, switch
+  locations, transformers or reactive power compensation assets.
+
+- **Distribution networks:**
+  Using Voronoi cells to aggregate load and generator data to transmission
+  network substations ignores the topology of the underlying distribution network,
+  meaning that assets may be connected to the wrong substation.
+
+- **Power Demand:**
+  Assumptions
+  have been made about the distribution of load in each country proportional to
+  population and GDP that may not reflect local circumstances.
+  Openly available
+  data on load time series may not correspond to the true vertical load and is
+  not spatially disaggregated; assuming, as we have done, that the load time series
+  shape is the same at each node within each country ignores local differences.
+
+- **Currently installed renewable capacities:** 
+  Information on existing wind, solar and small hydro, geothermal, marine and
+  biomass power plants are excluded from the dataset because of a lack of data
+  availability in many countries. Approximate distributions of wind and solar
+  plants in each country can be generated that are proportional to the capacity
+  factor at each location.
+
+- **Hydro-electric power plants:**
+  The database of hydro-electric power plants does not include plant-specific
+  energy storage information, so that blanket values based on country storage
+  totals have been used. Inflow time series are based on country-wide approxima-
+  tions, ignoring local topography and basin drainage; in principle a full hydro-
+  logical model should be used.
+
+- **International interactions:**
+  Border connections and power flows to Russia,
+  Belarus, Ukraine, Turkey and Morocco have not been taken into account; is-
+  lands which are not connected to the main European system, such as Malta,
+  Crete and Cyprus, are also excluded from the model.