add figures, text and refs for water4energy implementation

source/bibs/main.bib

@@ -995,10 +995,10 @@ @article{fritz_highlighting_2011
 
 
 @article{herrero_global_2013,
-  author = {Herrero, M. and Havlik, P. and Valin, H. and Rufino, M.C. and Notenbaert, A.M.O. and Thornton, P.K. and Blummel, M. and Weiss, F. and Obertsteiner, M.},
-  title = {Global livestock systems: biomass use, production, feed efficiencies and greenhouse gas emissions},
+	author = {Herrero, M. and Havlik, P. and Valin, H. and Rufino, M.C. and Notenbaert, A.M.O. and Thornton, P.K. and Blummel, M. and Weiss, F. and Obertsteiner, M.},
+	title = {Global livestock systems: biomass use, production, feed efficiencies and greenhouse gas emissions},
 	journal = {Proceedings of the National Academy of Sciences},
-  type = {Journal Article},
+	type = {Journal Article},
 	volume = {110},
 	issn = {0027-8424},
 	number = {52},
@@ -1477,3 +1477,80 @@ @article{mcjeon_gas_2014
 	pages = {482-485},
 	year = {2014}
 }
+
+@article{meldrum_2013,
+	title = {Life cycle water use for electricity generation: {A} review and harmonization of literature estimates},
+	author = {Meldrum, James and Nettles-Anderson, Syndi and Heath, Garvin and Macknick, Jordan},
+	journal = {Environmental Research Letters},
+	volume = {8},
+	number = {1},
+	pages = {015031},
+	year = {2013},
+	publisher = {IOP Publishing}
+}
+
+@article{fricko_2016,
+	title = {Energy sector water use implications of a 2 $^\circ${C} climate policy},
+	author = {Fricko, Oliver and Parkinson, Simon C and Johnson, Nils and Strubegger, Manfred and van Vliet, Michelle TH and Riahi, Keywan},
+	journal = {Environmental Research Letters},
+	volume = {11},
+	number = {3},
+	pages = {034011},
+	year = {2016},
+	publisher = {IOP Publishing}
+}
+
+@article{parkinson_2019,
+	title = {Balancing clean water-climate change mitigation trade-offs},
+	author = {Parkinson, Simon and Krey, Volker and Huppmann, Daniel and Kahil, Taher and McCollum, David and Fricko, Oliver and Byers, Edward and Gidden, Matthew J and Mayor, Beatriz and Khan, Zarrar and others},
+	journal = {Environmental Research Letters},
+	volume = {14},
+	number = {1},
+	pages = {014009},
+	year = {2019},
+	publisher = {IOP Publishing}
+}
+
+@article{zhai_2010,
+	title = {Performance and cost of wet and dry cooling systems for pulverized coal power plants with and without carbon capture and storage},
+	author = {Zhai, Haibo and Rubin, Edward S},
+	journal = {Energy Policy},
+	volume = {38},
+	number = {10},
+	pages = {5653--5660},
+	year = {2010},
+	publisher = {Elsevier}
+}
+
+@article{zhang_2014,
+	title = {Water- carbon trade-off in {C}hina`s coal power industry},
+	author = {Zhang, Chao and Anadon, Laura Diaz and Mo, Hongpin and Zhao, Zhongnan and Liu, Zhu},
+	journal = {Environmental science \& technology},
+	volume = {48},
+	number = {19},
+	pages = {11082--11089},
+	year = {2014},
+	publisher = {ACS Publications}
+}
+
+@article{loew_2016,
+	title = {Marginal costs of water savings from cooling system retrofits: {A} case study for {T}exas power plants},
+	author = {Loew, Aviva and Jaramillo, Paulina and Zhai, Haibo},
+	journal = {Environmental Research Letters},
+	volume = {11},
+	number = {10},
+	pages = {104004},
+	year = {2016},
+	publisher = {IOP Publishing}
+}
+
+
+@article{Raptis_2016_powerplant_data,
+	author = {Raptis, Catherine E. and Pfister, Stephan},
+	title = {{Global freshwater thermal emissions from steam-electric power plants with once-through cooling systems}},
+	journal = {Energy},
+	volume = {97},
+	pages = {46-57},
+	keywords = {Power plants; Once-through cooling; Heat emissions; Thermal pollution; Global; Environmental impact},
+	year = {2016}
+}

source/index.rst

@@ -21,6 +21,7 @@ We thank Edward Byers, Jessica Jewell, Simon C. Parkinson, Narasimha D. Rao for
    energy/index
    macro
    land_use/index
+   water/index
    emissions/index
    climate/index
    bibliography

source/water/index.rst

@@ -1,2 +1,71 @@
 Water
 ============
+
+The water withdrawal and return flows from energy technologies are calculated in 
+MESSAGE following the approach described in Fricko et al., (2016) :cite:`fricko_2016`.
+Each technology is prescribed a water withdrawal and consumption intensity (e.g., m3 per kWh)
+that translates technology outputs optimized in MESSAGE into water requirements and return
+flows. 
+
+.. _fig-ppl_energy_balance:
+.. figure:: /_static/ppl_energy_balance.png
+   :width: 320px
+   :align: right
+
+   Simplified power plant energy balance.
+
+For power plant cooling technologies, the amount of water required and energy dissipated
+to water bodies as heat is linked to the parameterized power plant fuel conversion efficiency (heat
+rate). Looking at a simple thermal energy balance at the power plant (:numref:`fig-ppl_energy_balance`), total combustion 
+energy (:math:`E_{comb}`) is conveterted into electricity (:math:`E_{elec}`), emissions (:math:`E_{emis}`)
+and additional thermal energy that must be absorbed by the cooling system (:math:`E_{cool}`):
+
+:math:`E_{comb} = E_{elec} + E_{emis} + E_{cool}`
+
+Converting to per unit electricity, we can estimate the cooling required per unit of electricity generation 
+(:math:`\phi_{cool}`) based on average heat-rate (:math:`\phi_{comb}`) and heat lost to emissions 
+(:math:`\phi_{emis}`), and this data is identified from the literature :cite:`fricko_2016`.
+
+:math:`\phi_{cool} = \phi_{comb} - \phi_{emis} - 1`
+
+With time-varying heat-rates (i.e., :math:`t =0,1,2,...`) and a constant share of energy to emissions and electricity:
+
+:math:`\phi_{cool}[t] = \phi_{comb}[t] \cdot \left( \, 1 - \dfrac{\phi_{emis}}{\phi_{comb}[0]} \, \right) - 1`
+
+Increased fuel efficiency (lower heat-rate) reduces the cooling requirement per unit of electricity generated.   
+This enables heat rate improvements for power plants represented in MESSAGE to be translated into
+improvements in water intensity. Water withdrawal and consumption intensities for power plant
+cooling technologies are calibrated to the range
+reported in Meldrum et al., (2013) :cite:`meldrum_2013`. Additional parasitic electricity demands from recirculating
+and dry cooling technologies are accounted for explicitly in the electricity balance calculation. All
+other technologies follow the data reported in Fricko et al.
+(2016) :cite:`fricko_2016`. 
+
+A key feature of the implementation is the representation of power plant cooling
+technology options for individual power plant types (:numref:`fig-cooling_implement1`).
+Each power plant type that requires cooling in MESSAGE 
+is connected to a corresponding cooling technology option (once-through, recirculating or
+air cooling), with the investment into and operation of the cooling technologies included in the
+optimization decision variables :cite:`parkinson_2019`. This enables MESSAGE to choose the type of cooling technology
+for each power plant type and track how the operation of the cooling technologies impact water
+withdrawals, return flows, thermal pollution and parasitic electricity use. 
+
+.. _fig-cooling_implement1:
+.. figure:: /_static/cooling_implement1.png
+   :width: 820px
+   :align: center
+
+   Implementation of cooling technologies in the MESSAGE IAM.
+
+Costs and efficiency for
+cooling technologies are estimated following previous technology assessments :cite:`zhai_2010,zhang_2014,loew_2016`. 
+The initial distribution of cooling technologies in each region
+and for each technology is estimated with the dataset described in Raptis and Pfister (2016) :cite:`Raptis_2016_powerplant_data`.
+The shares estimated at the river basin-scale are depcited in :numref:`fig-cooling_implement2` .   
+
+.. _fig-cooling_implement2:
+.. figure:: /_static/cooling_implement2.png
+   :width: 820px
+   :align: center
+
+   Average cooling technology shares across all power plant types at the river basin-scale.