Merge pull request #4 from Adam-Dvorak1/improve-doc

Adding hydrogen and oil-based products sections. Add one figure

doc/supply_demand.rst

@@ -145,22 +145,46 @@ 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)
 
+$$
+CH_4 + H_2O → CO + 3H_2
+$$
+
+combined with a water-gas shift reaction
+
+$$
+CO + H_2O → CO_2 + H_2
+$$
+
+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.
+
+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  
 ====================================
@@ -200,15 +224,26 @@ Solid biomass supply
 Only wastes and residues from the JRC ENSPRESO biomass dataset.
 
 
-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