1 ENERGY & CLIMATE ASSESSMENT TEAM National Risk Management Research Laboratory U.S. Environmental Protection Agency Office of Research and Development The Impact of CO 2 Emission Reductions on U.S. Electric Sector Water Use William Yelverton, Colin Cameron, Rebecca Dodder November 27, 2011 July 13, 2011

2 The objective of this presentation is to provide an update on, but not definitive conclusions from, current analyses of the interactions between electricity generation technology choices and water use in the U.S. while moving toward a lower- carbon energy system. Objective

3 Overview of MARKAL energy system model and its application to assess water use Linkages between electricity production and water resources Implications of CO 2 reduction scenarios on water use –Regional differences –Comparisons to estimates of water availability Discussion and future directions Outline

4 MARKAL Energy Systems Model Primary energy resourcesEnergy conversionEnd-use sectors

5 The MARKAL energy systems model selects the least cost technology and fuel pathway to meet current and future energy demands, while adhering to user-defined constraints –The model also accounts for material flows and emissions of interest Water factors were added to electricity generation technologies to track water withdrawals and consumption –Source: Macknick et al., A Review of Operational Water Consumption and Withdrawal Factors for Electricity generating Technologies, NREL, 2011 –Existing coal, natural gas, and nuclear generation was disaggregated to distinguish between capacity with open versus recirculating cooling technologies –CCS technologies (new and retrofit) are also included Primary focus is water usage, not capturing water quality implications or downstream temperatures Accounting for water in MARKAL

6 The U.S. electric sector accounts for 41% of all freshwater withdrawals and 6% of all water consumption (Kenny et al., Estimated use of water in the United States in 2005, USGS, 2009) –For comparison, agriculture accounts for 37% Electricity demand is projected to increase 27% by 2035 (EIA Annual Energy Outlook 2012) –Future system changes (e.g. a transition to electric vehicles) could force even greater increases Thermoelectric power plants generate 90% of all electricity produced in the U.S. and require large amounts of water for cooling –Cooling systems have greatest impact on water use –Certain ancillary systems such as CCS can have large water requirements as well –Most renewable technologies, such as wind and solar PV, require virtually no water per unit of electricity generated Water Use in the Electric Sector

7 When water supply is compromised, generation from thermoelectric facilities may be reduced or units may be forced to temporarily shut down Examples of water resource effects: –An increase in cooling water intake temperature from 70° to 90°F can reduce electricity output 5% (Rising Temperatures Undermine Nuclear Power’s Promise, UCS, 2007) –Facility unable to keep temperature of cooling water discharge below predetermined (state, municipality, etc.) thresholds for water quality –Water level of cooling water source falls below intake structures Electric Sector Vulnerability to Changes in Water Resources

8 Projected Changes in Available Precipitation (Roy et al., 2011) Roy et al., Changes in available precipitation from 2005 to 2050 in inches/yr values are based on 50th percentile an ensemble of 16 GCMs and represent conditions between 2040 and 2059.

9 Projected Water Temperature Increases (Van Vliet et al., 2012) Van Vliet et al (a)Projected changes in mean river water temperature. (b) Mean number of days per year that 27 °C inlet water temperature limit is exceeded for the 2040s and 2080s relative to the control period (1971–2000). Regions with projected decreases in low flows of more than 25% are hatched. a b

10 Examples of Facility Shutdowns Due to Cooling Water Issues Source: Seattle Times, 2012 Exelon Quad Cities Generating Station Cordova, IL, August 2006 – 1.8 GW Source: Nuclear Regulatory Commission Brown’s Ferry Nuclear Power Plant Athens, AL August 2007 – 3.5 GW Donald C. Cook Nuclear Plant Bridgman, MI, July 2006 – 2.3 GW Source: Nuclear Regulatory Commission Millstone Nuclear Power Station Waterford, CT, August 2012 – 2.2 GW Source: Nuclear Regulatory Commission

11 How might reductions in U.S. energy system CO 2 emissions impact electric sector water use?

12 Four scenarios for U.S. energy system-wide CO 2 reduction analyzed with EPAUS9r database (calibrated to AEO 2012) a)MARKAL base case (BAU) b)10% reduction in system CO 2 from BAU by 2055 c)25% reduction in system CO 2 from BAU by 2055 d)50% reduction in system CO 2 from BAU by 2055 CO 2 Reduction Scenarios

13 50% Reduction: CO 2 Emissions by Sector The model first chooses to maximize reductions in electricity production –Technology choices made vary by geographic region Reductions from the transportation sector begin in 2040 with a shift toward plug-in hybrid and electric light duty vehicles –This causes increased electricity demand

14 Regional Electricity Production by Technology, Base vs. 50% Reduction Scenarios in 2055

15 Electric Sector Effects Electric sector CO 2 emissions and water withdrawals follow similar trend of system-wide CO 2 reductions Water consumption tends to increase with higher CO 2 reductions –Coinciding with model’s election to utilize CCS and nuclear

16 Electric Sector Water Withdrawals by Region Trillions of Gallons of Water

17 Electric Sector Water Consumption by Region Trillions of Gallons of Water

18 Model results suggest reductions in system-wide CO 2 emissions could have significant impacts on electric sector water use Nationwide withdrawals tend to decrease proportionally to CO 2 reductions, potentially indicating decreased vulnerability to changes Consumption tends to increase as thermo- electric generation (with and without CCS) is continually relied on to meet increasing demand Discussion

19 Regionally, trends in withdrawals vs. consumption vary greatly with technology choice –For this reason, it is useful to utilize a model like MARKAL to run a range of scenarios for analysis Under the 50% CO 2 reduction scenario: –Some regions projected to be faced with most significant changes in water resources also choose to utilize low-water renewable technologies (e.g. Regions 4 and 7) –Other such regions rely heavily on water intensive technologies such as CCS and nuclear (e.g. Regions 2, 3, and 5) Water for withdrawals likely the more critical factor for electricity generation, but consumption issues may need to be considered at local levels Discussion

20 Questions? Thank you

21 Supplementary Information

22 Open vs. Recirculating Cooling Recirculating or Closed Loop Low withdrawal –Only to replenish that consumed –10 to 100 times less than open loop Consumes roughly twice that of an open loop system Space needed for cooling towers Utilized by most new facilities Once Through or Open Loop High withdrawal Low consumption Requires large water intake and continuous water resource Approximately 31% of existing thermoelectric capacity

23 MARKAL Water Factors of Interest TechnologyCooling Type WithdrawalConsumption gallons H 2 O/MWh Pulverized Coal Open Loop27, Recirculating Nuclear Open Loop44, Recirculating1, NGCC Recirculating Dry22 Coal w/CCSRecirculating1, NGCC w/CCSRecirculating Solar ThermalHybrid170 Solar PVN/A26 Wind & HydroN/A00 Source: Madknick et al. (2011), A Review of Operational Water Consumption and Withdrawal Factors for Electricity Generating Technologies. NREL: Golden, CO

24 National Electricity Generation by Technology for Each Scenario Base10% Reduction 25% Reduction50% Reduction

25 Light Duty Vehicle Technologies, 50% Reduction Scenario

26 Inter-regional Electricity Flows in 2055, 50% Reduction Scenario Arrow widths are proportional to volume of electricity flow in PJ

27 Purpose of using a model like MARKAL o Develop and examine internally consistent scenarios of energy system evolution and anticipating environmental consequences o Assess the potential roles of specific technologies in meeting policy goals o Identify important system interactions and potential unintended consequences o Consideration of uncertainties in fuel prices, technologies, and policy How the energy system evolves will have profound impacts on our environment, including climate, air and water MARKAL and energy-environmental analyses

28 Current coverage of sectors Electricity generation All electric generating units (except hydropower) Includes carbon capture and sequestration (CCS) Updating factors to reflect open vs. closed systems Resource extraction Coal (not regionally specific) Uranium Not natural gas, yet Petroleum-based fuels Crude oil extraction (domestic only) Petroleum refining Biofuels Biomass irrigation (regionally specific) –Allocated between crops and crop residues (stover) where applicable Biofuel refining