Water-Energy Nexus Moving the People or Resources

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					                                                                                Water-Energy Nexus: Moving the People or Resources?                                                                                                                                                                                                                                                                                         Vanderbilt Institute
                                                                                                                                                                                                                                                                                                                                                                                                                              for Energy and
                                                                                                                                                A hypothetical consideration of addressing sustainability                                                                                                                                                                                                                      Environment
                                                                                                                                                                              D. Perrone, J. Murphy & G. Hornberger
INTRODUCTION                                                                                                          METHODS                                                                                                                                                      Table 4: Model Assumptions
Energy and water are inexplicably linked, yet rarely do communities collect enough of the                             Conceptual models were developed (Figures 2 & 3) and quantified according to various                                                                             Major Model Assumptions                                          Justification                                                      Implications
appropriate data to understand how the connection may affect their community. The                                     stages of energy and water use. Tables 2 and 3 describe the model by each stage and                                                                          No significant energy efficiency technological Most detailed and recent data for energy used during            If the new technology is more efficient, like it often is, the model
interrelated nature of these resources is even more evident when their supplies are scarce. We                        provide insight to the user input required for the model. Due to data constraints and                                                                        advances for the fuel cycle & electricity      production are from 1994 (Gleick)                               will over-calculate consumptive water
                                                                                                                                                                                                                                                                                   generation since the 1990’s
qualitatively describe communities that lack sufficient local water and energy resources for                          difficulties defining conditions, various assumptions were made for the model (Table 4).                                                                     National and regional averages approximate     Water and energy data is often not reported or collected and    Results may be higher or lower than actual
their demands as Resource Islands.                                                                                                                                                                                                                                                 local scenarios                                very hard to track down

                                                                                                                                                                                                                                                                                   Negligible water is lost through evaporation   Evaporative loss is suggested to be 2-3% (CAP) and quality      The total amount of water may be high if accounting for ‘lost’
Resource Islands                                                                                                                                                                                                                                                                   and leaky pipes                                of local distribution system was not taken into account         water during transportation
•  Resource Islands: Communities located considerable distances from their water and energy                                                                                                                                                                                        Only the community’s reported, direct water    This study does not address a life cycle approach so a cradle   Water and energy associated with construction and maintenance
resources                                                                                                                                                                                                                                                                          and energy demands were used                   to grave analysis was not needed                                of equipment (water & energy) is not accounted for

                                                                                                                                                                                                                                                                                   Community is considered an incorporated        Boundaries are hard to define due to inconsistency in water     Results do not include suburbs or the surrounding metropolitan
•  Ecological Definition: “Resource islands form when individual plants influence the                                                                                                                                                                                              city                                           and energy boundaries                                           area
surrounding soil to alleviate nutrient and temperature stress and foster seedling survival and
growth” (Carrillo-Carcia et al 2000).
   •  Definitions are similar in terms of describing a more-livable micro-environment in an                                                                                                                                                                                        RESULTS
   otherwise inhospitable desert ecosystem.                                                                                                                                                                                                                                        Virtual water and energy resources (the amount of water used in the production of energy and the amount of energy used in the
                                                                                                                                                                                                                                                                                   acquisition of water) were analyzed for Tucson, Arizona. Inclusion of virtual water for energy more than doubles the amount of
•  Example: City of Tucson located in Arizona, United States of America                                                                                                                                                                                                            water consumed by the City of Tucson (Figure 3). However, virtual energy used in the acquisition of water is an insignificant portion
    •  Over 335 miles (540 km) from one of its main water sources and 200+ miles (320 km)                                                                                                                                                                                          of the total energy used by the City of Tucson (Figure 4). For the case study, two scenarios were considered to address the
    from its power supplies (Figure 1).                                                                                                                                                                                                                                            hypothetical question of moving the people to the resources and the resources to the people for Tucson: Scenario 1 Current
                                                                                                                                                                                                                                                                                   Conditions (i.e. moving the resources to the people) and Scenario 2 Hypothetical Conditions (i.e. moving the people to the resources)
Problem Statement                                                                                                                                                                                                                                                                  (Figures 5 and 6).
Geography (i.e. distance from available water and energy resources) and community size (i.e.
demand) directly affect energy and water use. However, quantifying water-energy resource                              Figure 2: Water for Energy (left) and Energy for Water (right)                                                                                                                                                                                  Water

use is difficult to accomplish, much less comprehend, without a functional conceptual model.
Current water-energy nexus models are not useful for city planning or community
                                                                                                                      Conceptual Diagrams
development as they call for data that are not typically collected by communities, inevitably
using ‘hypothetical’ cities or data.                                                                                   Table 2: Water for Energy Model Description
                                                                                                                                                Fuel Cycle                          Transport                    Electricity Production                 Transmission
                                                                                                                                            Uses average water           •  Uses heat content of the             •  Uses average water              •  Uses average
                                                                               Project Objectives

                                                                                                                                            consumption for the          transportation fuel, or pipeline        consumption data for power         transmission line losses
                                                                                                                                            processes needed to          efficiency, and distance to calculate   plants based on their energy       and efficiencies to
                                                                   s reg

                                                                               1.)    To develop a model using

                                                                                                                                            make the energy              the total amount of energy              source and cooling technology      calculate the energy lost in

                                                                               national and regional averages of                            source consumable by         consumed for transport                  •  Calculations are dependent on   transmission over distances
                                                             n Ba

                                                                               energy for water and water for                               users                        •  Calculates the water for the         technology                         •  Assumed end user does
                                                         4 Co

                                                                                                                                            •  Exploration               energy consumed in transport by              •  Cooling towers consume     not alter energy, so no
                                                                                                                                                                                                                                                                                   Figure 3: Tucson water demand                                              Figure 5: Tucson water for energy scenario analysis

                                                                               energy consumption                                           •  Extraction & mining       using the energy source’s water              ~2X the water that once-      water is used by the end
                                                                                                                                            •  Recovery

                                                                                                                                                                         consumption in its fuel cycle                through plants consume        user for energy

                                                                               2.) Enable communities to acquire a                          •  Processing                •  Inherentlydeals with transport       •  Does not incorporate            consumption


                                                                                                                                            •  Refining                  mode efficiency                         geographical variations in plant
               Co                                                              cursory understanding of the                                 •  Enrichment                                                        consumption

                     ad                                                        potential connectedness and impacts                          •  Growing (biomass)


                          ive                                                  to water and energy use                                      •  Energy sources            •  Location of energy sources,          •  Energy sources                  •  Transmission line

                             r                                                                                                                   •  Coal, oil, natural   electric generating plants, and              •  Coal, oil, natural gas,    distance from generating
                                                                                                                         USER INPUT

                                                                                                                                                 gas, nuclear,           community                                    nuclear, renewables           facility to community
                                                                               3.) Indicate potential directions of                              renewables              •  Distance between energy sources      •  Amountof each source            •  Transmission line
         Californ                                                              energy for water and water for                               •  Amountof each             and electric plants or community             •  KWh/source/yr              efficiency
                    ia Coast                           , NM                                                                                 source                       •  Transport mode                       •  Type of generating plant
                            al Impo
                                   rts           Luna                          energy data collection
                                                                                                                                                 •  KWh/source/yr        •  Transport mode efficiency                 •  Energy sources used
                                                 El Paso                                                                                                                       •  Distance/volume fuel                •  Cooling technology used
                                                Pe                             4.) Use the City of Tucson, Arizona,                                                            •  Pipeline efficiency
                                 Tucson, AZ   Ba rm
                                                sin ian                        USA as a case study to highlight the                         • (1994). "Water and Davis, S. C., S. W. Diegel, et al.              • Gleick, P. H. (1994). "Water     Davis, S. C., S. W. Diegel,

 Adapted from asu.edu                                                                                                                                                                                                                                                                         Virtual

                                                                               impact of geographic location,                               Energy." Annual      (2009). Transportation Energy Data              and Energy." Annual Review of      et al. (2009).
                                                                               distance from water and energy                               Review of Energy and Book.                                           Energy and the Environment         Transportation Energy
          Natural gas                 Electricity source                                                                                    the Environment 19:                                                  19: 267-299.                       Data Book.
                                                                               resources                                                    267-299.                                                                                                                               Figure 4: Tucson energy demand                                             Figure 6: Tucson energy for water scenario analysis
          Transport Fuels             Water source
                                                                                                                      Table 3: Energy for Water Model Description                                                                                                                  DISCUSSION
Figure 1: Tucson site map and Resource                                                                                                                                                                                        Local
                                                                                                                                                          Source                             Treatment                                                     End User                The scenario analysis indicates that Tucson is a resource island. For virtual water and energy, transportation and extraction,
Island depiction.                                                                                                                                                                                                          Distribution                                            respectively, are the most sensitive stages (Figure 5 and 6), confirming the reliance on distant resources to provide a more hospitable
                                                                                                                                            Energy used to retrieve water           Energy used to treat water to      Energy used to distribute Energy expended in the use

                                                                                                                                                                                                                                                                                   environment in an otherwise arid, resource-deprived desert. If the people were, hypothetically, moved to the resources, less water and
                                                                                                                                            from the source area and moveit         usable a standards                 potable and recycled      of water by the ‘End
Table 1: Characteristics of the City of Tucson, Arizona, USA                                                                                to treatment facility                   •  Potable                         water to end users        User’ (e.g. heading)              energy would be consumed. Although the magnitude difference between scenario one and two is far greater for virtual energy, it only
                                                                                                                                            • Surface water (conveyance)            • Recycled                                                                                     accounts for 1% of Tucson’s total (virtual and actual) energy (Figure 4 and 6). End use is not important for water for energy
                    o  32°08'N, 110°57'W                                                                                                    •  Groundwater (pumping)
                                                                                                                                                                                                                                                                                   considerations but it plays a significant, if not dominant, role in energy for water. Due to difficulties quantifying the end-use stage
   Location         o  Southern portion of Arizona, USA (Figure 1)                                                                          •  Recycled water (collection)
                                                                                                                                            •  Desalination (movement)                                                                                                             (e.g. heating water) of energy for water, this was not included in this case study. Rough estimates, however, approximated end-use
                    o  Basin and Range: broad desert valleys and small isolated mountain ranges                                                                                                                                                                                    virtual energy as three orders of magnitude higher than all other stages combined. International imports of energy materials were not
                    o  Groundwater aquifers are small and often isolated from adjacent basins                                               •  Water sources & volume / year        •  Source of water                 •  Average electricity      •  Population of community      considered in this study due to difficulty identifying source location. Including international import distances in the scenario analysis

                    o  Located in the Tucson basin, a valley composed of alluvial fan sediments                                             • Elevation of source                   •  Size of treatment plant         used for distribution                                       of water for energy would greatly increase the magnitude of scenario one through the transportation stage (Figure 5). Economies of
  Geography                                                                                                                                 •  Elevation of treatment facility      •  Level of treatment              pumping
                    o  Santa Cruz River is adjacent to the City of Tucson, currently intermittent                                                                                                                                                                                  scale may prove important when considering water and energy use and will be further investigated.
                                                                                                                                            • Pump efficiency                       •  Or type of technology           •  Average electricity rate
                    flow controlled by wastewater discharge
                                                                                                                                            •  Surface water, groundwater &         Energy intensity rates from      Conversion of electricity      KWh per person
                    o  Sun belt: Arid to semi-arid climate
                                                                                                                          MODEL FRAMEWORK

                                                                                                                                            desalination:                           published literature for water   used for local pumping         consumption based on
                    o  Low annual precipitation (approximately 27cm / year)                                                                     general horsepower equation         treatment depending on source, to KWh/AF:                       California energy utility
    Climate                                                                                                                                        hp=(y*Q*H)/ (550*e)              technology and quantity treated.       Ewp = Xe/Re              reporting.                     Although this model does not use site specific data, it has the potential to expose a community to the data collection needs of water-
                    o  Average temperature range from 52° to 85°F (11° to 30°C)
                                                                                                                                            Where:                                                                   Where:                                                        energy analysis. The aim is to make communities more aware of the nexus so future planning can account for the intimate
                    o  6.5% increase in population over the past 6 years                                                                    Y = specific weight of water            • Surface water (e.g. SBW        Ewp = Energy used for          Source data: California
                                                                                                                                            Q = flow (cubic feet per second)        Consulting, Inc 2006 Municipal pumping (KWh/AF)                 Energy Commission, 2005        relationship between water and energy resources.
  Population        o  534,685 people, current population as of 2006
                                                                                                                                            H = total head (feet)                   Water Treatment Plant Energy Xe = Average electricity           California's water energy
             o  96% of people live within metropolitan Tucson                                                                               E = pump efficiency                     Baseline Study Prepared for the costs for distribution          relationship Final Staff
             o  Approximately 71% of Tucson residents commute to work alone
Demographics (compared to 75% U.S. nationally)                                                                                              •  Recycled water: Price for
                                                                                                                                                                                    Pacific Gas and Electric
                                                                                                                                                                                    Company, Bellevue, WA p 55) rate
                                                                                                                                                                                                                     Re = Average electricity       Report Prepared in Support
                                                                                                                                                                                                                                                    of the 2005 IEPR Proc.
                                                                                                                                            pumping and electricity rate to                                                                         (Sacramento, CA)               This work was supported by the Vanderbilt Institute for Energy and Environment. We also thank the Departments of CEE & EES for
 & Lifestyle o  3.5% use public transportation.                                                                                             infer average cost of collection                                                                        CEC-700-2005-011-SF            their support.