The Impact of CO 2 Emission Constraints on U.S. Electric Sector Water Use Colin Cameron 1, William Yelverton 2, Rebecca Dodder 2, Jason West 1 1 University of North Carolina at Chapel Hill, Chapel Hill, NC, USA 2 Office of Research and Development, Environmental Protection Agency, Research Triangle Park, NC, USA The U.S. electric power sector’s reliance on water makes it vulnerable to increased water temperature and drought resulting from climate change. Here we analyze how constraints on U.S. energy system carbon dioxide (CO 2 ) emissions could affect water withdrawal and consumption in the U.S. electric sector through EPA’s U.S. 9-region (EPAUS9r) MARKAL least-cost optimization energy systems model with updated water use factors for electricity generating technologies is used for this analysis. Four scenarios of total energy system CO 2 emission reductions were created and analyzed for their effect on electric sector technology mix and associated water use. Constraints were calculated as percent reductions from year 2005 base case EPAUS9R model results. Constraints first take effect in 2015 and decrease linearly in each time step thereafter until they achieve target reductions in Base: No constraints on CO % CO 2 Reduction: CO 2 emissions decrease 10% by % CO 2 Reduction: CO 2 emissions decrease 25% by % CO 2 Reduction: CO 2 emissions decrease 50% by 2055 Figures 2A – D. Electricity production in petajoules (PJ) by technology for each scenario from 2005 to Figure 2E. Electricity production (PJ) by technology in the Base case (left bar) and the 50% CO 2 Reduction scenario (right bar) in each region in E. Regional Production, 2055 Figure 3A. Water consumption (10 12 gallons) for the electric sector for all scenarios. 3B. Water withdrawal (10 12 gallons) in the electric sector for all scenarios. 3C. Water consumption (10 12 gallons) for each region in 2055 for the base (left bar) and the 50% CO 2 reduction scenarios (right bar). 3D. Water withdrawal (10 12 gallons) for each region in 2055 for the base (left bar) and the 50% CO 2 reduction scenarios (right bar). CCS comes online Coal Retirement 3B. Water Withdrawal3A. Water Consumption 3D. Water Withdrawal, 20553C. Water Consumption, 2055 CO 2 constraints increase implementation of low water- intensity technologies (wind and solar) in regions 4,7, and 8. CO 2 constraints increase implementation of high water-intensity technologies (nuclear and CCS) in regions 2,3, and 5. Figure 1A. U.S energy system CO 2 emissions in millions of tons CO 2 (MT CO 2 ). 1B. CO 2 emissions from the electric sector (MT CO 2 ). 1C. CO 2 emissions by sector in the 50% CO 2 Reduction scenario (MT CO 2 ). 1D. Differences in light duty vehicle technology use between Base and 50% Reduction scenarios in billions of vehicle miles travelled (bln-VMT). 1A. Energy System CO 2 Emissions 1D. Transportation Sector Change 1B. Electric Sector CO 2 Emissions Introduction CO 2 Emission Reductions Electricity Production by Technology and Region Model results suggest CO 2 constraints could lead to: Increased use of low water-intensity renewable energy technologies such as wind and solar in western regions (regions 4, 7-9). Replacement of old thermoelectric power plants with new nuclear power and natural gas combined cycle CCS plants using more advanced cooling systems in eastern regions (regions 1-3, 5-6) These changes in electric sector technology mix: Reduce aggregate national water withdrawal from base scenario levels in each CO 2 Reduction scenario Increase national water consumption in the 50% CO 2 Reduction scenario Decreased electric sector water withdrawal could reduce aggregate national electric sector vulnerability to drought and high water temperatures Heavy reliance on nuclear power, minimal decrease in water withdrawal and massive increases in water consumption could cause high vulnerability to climate change in the South-East (region 5) Increased water consumption in the electric sector could increase competition with other sectors Water Use Discussion 1C. CO 2 Emissions by Sector 2A. Base 2D. 50% CO 2 Reduction 2B. 10% CO 2 Reduction 2C. 25% CO2 Reduction Vehicle Electrification Electricity generation increases with new demand from transportation sector Existing coal plant retirement Natural gas and coal CCS Increased use of renewables Increased electricity use Decreased fossil fuel use Existing coal facilities maintained through model horizon Emissions reductions from electric and transportation sectors Nuclear power and CCS use increases water consumption