Merge branch 'improve-doc' of https://github.com/GormBruunAndresen/pypsa-eur-sec-mvp into improve-doc

doc/index.rst

@@ -26,8 +26,8 @@ PyPSA-Eur-Sec builds on the electricity generation and transmission
 model `PyPSA-Eur <https://github.com/PyPSA/pypsa-eur>`_ to add demand
 and supply for the following sectors: transport, space and water
 heating, biomass, energy consumption in the agriculture, industry 
-and industrial feedstocks. This completes the energy system and includes 
-all greenhouse gas emitters except waste management, agriculture, 
+and industrial feedstocks, carbon management, carbon capture and usage/sequestration. 
+This completes the energy system and includes all greenhouse gas emitters except waste management, agriculture, 
 forestry and land use.
 
 
@@ -41,9 +41,9 @@ patchy.
 We cannot support this model if you choose to use it.
 
 .. note::
-    You can find showcases of the model's capabilities in the
+    You can find showcases of the model's capabilities in the Supplementary Materials of the 
     preprint `Benefits of a Hydrogen Network in Europe
-    <https://arxiv.org/abs/2207.05816>`_, a `paper in Joule with a
+    <https://arxiv.org/abs/2207.05816>`_, the Supplementary Materials of the `paper in Joule with a
     description of the industry sector
     <https://arxiv.org/abs/2109.09563>`_, or in `a 2021 presentation
     at EMP-E <https://nworbmot.org/energy/brown-empe.pdf>`_.

doc/supply_demand.rst

@@ -55,9 +55,7 @@ Oil and gas boilers
 Heat pumps
 -------------
 
-
-
-Air-to-water heatpumps are used in urban central bus. 
+Either air-to-water or ground-to-water heat pumps are implemented.
 
 They have coefficient of performance (COP) based on either the
 external air or the soil hourly temperature.
@@ -147,34 +145,73 @@ Further information are given in the publication
 
 `Mitigating heat demand peaks in buildings in a highly renewable European energy system, (2021) <https://arxiv.org/abs/2012.01831>`_.
 
-
 Hydrogen demand
-==================
-
-Stationary fuel cell CHP.
-
-Transport applications (heavy-duty road vehicles, liquid H2 in shipping).
-
-Industry (ammonia, precursor to hydrocarbons for chemicals and iron/steel).
+=============================
 
+Hydrogen is consumed in the industry sector (link to industry) to produce ammonia [link to ammonia industry section] and direct reduced iron (DRI) [link to DRI industry section]. Hydrogen is also consumed to produce synthetic methane [link to section “Methane supply”] and liquid hydrocarbons [link to fossil-oil based supply”] which have multiple uses in industry and other sectors. 
+Hydrogen is also used for transport applications (link to transport), where it is exogenously fixed. It is used in `heavy-duty land transport <https://github.com/PyPSA/pypsa-eur-sec/blob/3daff49c9999ba7ca7534df4e587e1d516044fc3/config.default.yaml#L181>`_ and as liquified hydrogen in the shipping sector [add link to shipping sector]. Furthermore, stationary fuel cells may re-electrify hydrogen (with waste heat as a byproduct) to balance renewable fluctuations [Add a link to the section where we describe the Electricity sector and how storage is modelled there]. The waste heat from the stationary fuel cells can be used in `district-heating systems <https://github.com/PyPSA/pypsa-eur-sec/blob/3daff49c9999ba7ca7534df4e587e1d516044fc3/config.default.yaml#L256>`_.
 
 Hydrogen supply
-=================
+=============================
 
-Steam Methane Reforming (SMR), SMR+CCS, electrolysers.
+Today, most of the H2 consumed globally is produced from natural gas by steam methane reforming (SMR)
 
+$$
+CH_4 + H_2O → CO + 3H_2
+$$
 
-Methane demand
-==================
+combined with a water-gas shift reaction
 
-Can be used in boilers, in CHPs, in industry for high temperature heat, in OCGT.
+$$
+CO + H_2O → CO_2 + H_2
+$$
 
-Not used in transport because of engine slippage.
+SMR is included `here <https://github.com/PyPSA/pypsa-eur-sec/blob/3daff49c9999ba7ca7534df4e587e1d516044fc3/config.default.yaml#L245>`_. 
+PyPSA-Eur-Sec allows this route of H2 production with and without [carbon capture (CC)] (Link to section on Carbon Capture Storage and Utilization). These routes are often referred to as blue and grey hydrogen. Here, methane input can be both of fossil or synthetic origin.
 
-Methane supply
-=================
+Green hydrogen can be produced by electrolysis to split water into hydrogen and oxygen
+
+$$
+2H_2O → 2H_2 + O_2
+$$
+
+For the electrolysis, alkaline electrolysers are chosen since they have lower cost and higher cumulative installed capacity than polymer electrolyte membrane (PEM) electrolysers. The techno-economic assumptions are taken from the technology-data repository. Waste heat from electrolysis is not leveraged in the model.
+
+*Transport*
+
+Hydrogen is transported by pipelines. H2 pipelines are endogenously generated, either via a  greenfield H2 network, or by `retrofitting natural gas pipelines <https://github.com/PyPSA/pypsa-eur-sec/blob/3daff49c9999ba7ca7534df4e587e1d516044fc3/config.default.yaml#L262>`_). Retrofitting is implemented in such a way that for every unit of decommissioned gas pipeline, a share (60% is used in [link to H2 backbone study]) of its nominal capacity (exogenously determined in the `config file <https://github.com/PyPSA/pypsa-eur-sec/blob/3daff49c9999ba7ca7534df4e587e1d516044fc3/config.default.yaml#L266>`_.) is available for hydrogen transport. When the gas network is not resolved, this input denotes the potential for gas pipelines repurposed into hydrogen pipelines.
+New pipelines can be built additionally on all routes where there currently is a gas or electricity network connection. These new pipelines will be built where no sufficient retrofitting options are available. The capacities of new and repurposed pipelines are a result of the optimisation.
+
+*Storage*
+
+Hydrogen can be stored in overground steel tanks or `underground salt caverns <https://github.com/PyPSA/pypsa-eur-sec/blob/3daff49c9999ba7ca7534df4e587e1d516044fc3/config.default.yaml#L250>`_. For the latter, energy storage capacities in every country are limited to the potential estimation for onshore salt caverns within `50 km <https://github.com/PyPSA/pypsa-eur-sec/blob/3daff49c9999ba7ca7534df4e587e1d516044fc3/config.default.yaml#L251>`_ of shore to avoid environmental issues associated with brine solution disposal. Underground storage potentials for hydrogen in European salt caverns is acquired from `Caglayan et al. <https://doi.org/10.1016/j.ijhydene.2019.12.161>`_
+
+Methane demand  
+====================================
+                  
+Methane is used in individual and large-scale gas boilers, in CHP plants with and without carbon capture, in OCGT and CCGT power plants, and in some industry subsectors for the provision of high temperature heat[LINK TO INDUSTRY OVERVIEW]. Methane is not used in the trans- port sector because of engine slippage.
+
+Methane supply                          
+===================================
+
+In addition to methane from fossil origins, the model also considers biogenic and synthetic sources. `The gas network can either be modeled, or it can be assumed that gas transport is not limited <https://github.com/PyPSA/pypsa-eur-sec/blob/3daff49c9999ba7ca7534df4e587e1d516044fc3/config.default.yaml#L261>`_. If gas infrastructure is regionally resolved, fossil gas can enter the system only at existing and planned LNG terminals, pipeline entry-points, and intra- European gas extraction sites, which are retrieved from the SciGRID Gas IGGIELGN dataset and the GEM Wiki. 
+Biogas can be upgraded to methane. 
+Synthetic methane can be produced by processing hydrogen and captures CO2 in the Sabatier reaction 
+
+$$                   
+CO_2 + 4H_2 → CH_4 + 2H_2O
+$$
+
+Direct power-to-methane conversion with efficient heat integration developed in the HELMETH project is also an option. The share of synthetic, biogenic and fossil methane is an optimisation result depending on the techno-economic assumptions.
+                
+*Methane transport*
+            
+The existing European gas transmission network is represented based on the SciGRID Gas IGGIELGN dataset. This dataset is based on compiled and merged data from the ENTSOG maps  and other publicly available data sources. It includes data on the capacity, diameter, pressure, length, and directionality of pipelines. Missing capacity data is conservatively inferred from the pipe diameter following conversion factors derived from an EHB report. The gas network is clustered to the selected number of model regions. Gas pipelines can be endogenously expanded or repurposed for hydrogen transport. Gas flows are represented by a lossless transport model. Methane is assumed to be transmitted without cost or capacity constraints because future demand is predicted to be low compared to available transport capacities.
+
+The following figure shows the unclustered European gas transmission network based on the SciGRID Gas IGGIELGN dataset. Pipelines are color-coded by estimated capacities. Markers indicate entry-points, sites of fossil resource extraction, and LNG terminals.            
+    
+.. image:: ../graphics/gas_pipeline_figure.png
 
-Fossil, biogas, Sabatier (hydrogen to methane), HELMETH (directly power to methane with efficient heat integration).
 
 Biomass
 ============
@@ -183,6 +220,10 @@ Biomass supply
 ---------------
 Biomass supply potentials for each European country are taken from the `JRC ENSPRESO database <http://data.europa.eu/89h/74ed5a04-7d74-4807-9eab-b94774309d9f>`_ where data is available for various years (2010, 2020, 2030, 2040 and 2050) and scenarios (low, medium, high). No biomass import from outside Europe is assumed. More information on the data set can be found `here <https://publications.jrc.ec.europa.eu/repository/handle/JRC98626>`_.
 
+Solid biomass demand
+=====================
+
+
 The desired scenario can be selected in the pypsa-eur-sec `configuration <https://github.com/PyPSA/pypsa-eur-sec/blob/3daff49c9999ba7ca7534df4e587e1d516044fc3/config.default.yaml#L108>`_. The script for building the biomass potentials from the JREC ENSPRESO data base is located `here <https://github.com/PyPSA/pypsa-eur-sec/blob/3daff49c9999ba7ca7534df4e587e1d516044fc3/scripts/build_biomass_potentials.py#L43>`_. Consult the script to see the keywords that specify the scenario options.
 
 The `configuration <https://github.com/PyPSA/pypsa-eur-sec/blob/3daff49c9999ba7ca7534df4e587e1d516044fc3/config.default.yaml#L108>`_ also allows the user to define how the various types of biomass are used in the model by using the categories : biogas, solid biomass, and not included.
@@ -211,15 +252,26 @@ The model can only use biogas by first upgrading it to natural gas quality [link
 
 
 
-Oil product demand
-=====================
+Oil-based products demand
+========================
+Naphtha is used as a feedstock in the chemicals industry[LINK TO CHEMICAL INDUSTRY]. Furthermore, kerosene is used as transport fuel in the aviation sector[LINK TO AVIATION SECTOR]. Non-electrified agriculture machinery also consumes gasoline. 
+Land transport [LINK TO LAND TRANSPORT]  that is not electrified or converted into using H2-fuel cells also consumes oil-based products. While there is regional distribution of demand, the carrier is copperplated in the model, which means that transport costs and constraints are neglected. 
 
-Transport fuels, agriculture machinery and naphtha as a feedstock for the chemicals industry.
 
-Oil product supply
-======================
+Oil-based products supply 
+======================== 							
+Oil-based products can be either of fossil origin or synthetically produced by combining H2 [link to hydrogen] and captured CO2 [link to carbon capture] in Fischer-Tropsch plants		
 
-Fossil or Fischer-Tropsch.
+$$
+𝑛CO+(2𝑛+1)H_2 → C_{n}H_{2n + 2}  +𝑛H_2O
+$$
+
+with costs as included from the `technology-data repository <https://github.com/PyPSA/technology-data/blob/master/latex_tables/tables_in_latex.pdf>`_. The waste heat from the Fischer-Tropsch process is supplied to `district heating networks <https://github.com/PyPSA/pypsa-eur-sec/blob/3daff49c9999ba7ca7534df4e587e1d516044fc3/config.default.yaml#L255>`_. The share of fossil and synthetic oil is an optimisation result depending on the techno-economic assumptions.
+
+
+Oil-based transport
+======================== 		
+Liquid hydrocarbons are assumed to be transported freely among the model region since future demand is predicted to be low, transport costs for liquids are low and no bottlenecks are expected. 
 
 
 Industry demand