California’s -Water Nexus: Water Use in Generation Dana Larson, Cheryl Lee, Stacy Tellinghuisen, and Arturo Keller — Bren School of Environmental Management and Science, University of California, Santa Barbara

ater and energy are The following sources were The data were used to project the total inextricably linked. Large analyzed: bioenergy, , geothermal, water needs for California’s potential Wamounts of water are hydroelectric, natural gas, nuclear, oil, solar, future energy portfolios under the 2010 needed for energy production, and large and wind. High and low estimates for both and 2020 renewable portfolio standards amounts of energy are needed for the water withdrawn and water consumed were (RPS; see sidebar below). In addition, extraction, conveyance, treatment, and included in the data collection process. To scenarios were created for the year 2020 distribution of water. Historically, energy ensure the validity of the data, the 2005 that altered the primary energy sources, and water issues have been examined water withdrawals for electricity generation electricity generation technologies, and independently, which has led to: cooling technologies. These scenarios • planning for future electricity production While geothermal and included: 1) a -focused scenario without considering water needs; and in which future electrical generation growth coal constitute less was limited to natural gas and coal; 2) an • planning for a future domestic potable than a quarter of the advanced technologies scenario in which water supply and wastewater treatment integrated gasification combined cycle with the assumption that electricity will generation capacity …, (IGCC) and dry cooling technologies be readily available and affordable. they account for almost 90 percent of the freshwater were applied to the 2020 RPS portfolio; In the future, however, both the scarcity requirements. and 3) a water-efficient primary energy of freshwater and the cost of energy scenario that relies on the primary energy will likely become limiting factors of sources that our initial research identified as economic and population growth. This were projected for four counties in California water-efficient (rooftop solar photovoltaic, is particularly critical in California and compared to U.S. Geological Survey wind, and waste-based bioenergy). and other arid Southwestern states, (USGS) and California Department of This analysis considered only freshwater where population is projected to grow Water Resources (DWR) thermoelectric requirements for power generation, thus dramatically and climate change models water withdrawal estimates for the same seawater-cooled thermoelectric power suggest that freshwater supplies may counties. Projected water requirements plants and hydroelectric facilities were decrease significantly. Integrated planning closely agreed with USGS and DWR values excluded. Although the total volume of between the energy and water sectors for coastal counties. The projection for the seawater withdrawn for power generation therefore will be essential to meet one inland county showed some discrepancy, in California is far greater than that for rising demands for both resources. likely due to the large amount of reclaimed water used for power plant cooling there. freshwater, greater competition exists

How Much Water for Electricity? Renewable Portfolio Standards We reviewed peer-reviewed literature, industry and government sources, and To promote production (using offshore wind, ocean waves, and help boost the renewables market currents, or tides). primary research to collect quantitative as it matures, 24 states to date have water requirements pertaining to each The California RPS policy, the most adopted renewable portfolio standards stringent in the United States, was step of the electricity generation process. (RPS). These require sellers of electricity established in 2002, requiring retail The water input steps considered were to have a certain percentage of sellers of electricity to purchase different for each type of generation but “renewable power” in their mix. RPS 20 percent of their electricity from generally included agriculture, mining, policies usually mandate a gradual renewable resources by 2017. Because transportation, makeup water, processing, increase in the percentage over a number the state had already been generating cooling, cleaning, evaporative losses, and of years, and often involve a trading around 10 percent of its electricity mechanism whereby companies can sell other. For example, water is required at consumption by renewables and credits to those who haven’t met their several points in the process of generating the program enjoyed considerable requirements. electricity from coal. Initially, water early success, the time frame was is required for extraction (mining), sources typically accelerated to achieve the 20 percent processing (washing), fuel conversion include wind, geothermal, biomass, solar, goal by 2010, and a new goal of 33 (gasification), and finally cooling. , and ocean-based energy percent was set for 2020.

20 • September/October 2007 • Southwest Hydrology for freshwater resources. Further, while Water Use for Electricity Production seawater cooling may appear to be a likely Biogas alternative to the use of freshwater in energy BIOENERGY generation, growing concerns about negative Waste Products impacts to coastal ecosystems have shifted Dedicated Energy Crops 130+ interest away from this cooling method. Dry Cooling FOSSIL FUELS Wet Recirculating Cooling And the Results Are... Once-through Cooling Water requirements vary greatly, depending Dry Cooling GEOTHERMAL on the primary energy source, conversion Wet Recirculating Cooling technologies, and cooling technologies used Once-through Cooling (see figure, right). Overall, the data showed “Run of River” Facilities HYDROPOWER that the biggest water users are bioenergy Large Reservoir and Dam derived from dedicated energy crops (based Small Reservoir and Dam on average values for irrigated crops), CSP, Dish-Engine System hydroelectric facilities, and thermoelectric SOLAR facilities using once-through cooling. Waste- CSP, Parabolic Troughs based bioenergy, thermoelectric facilities CSP, Power Tower Plant using dry cooling, solar photovoltaics, and RV, Rooftop Panels WIND wind turbines require the least water. Medium-sized Farm Large-sized Farm Alternative Energy Scenarios 0 10 20 30 40 50 60 When the water requirements were applied to future energy scenarios, the total amount Average Water Withdrawals (gal/kWh) of water required varied (see figure below Water requirements are highest for electricity generated from irrigated crop-based biomass, right). Surprisingly, the fossil fuel-based hydroelectric power, and for thermoelectric generation using once-through cooling technology. Note: not all energy crops are irrigated, and regional irrigation differences are great. CSP = concentrating scenario projected for 2020 requires less solar power (power towers and parabolic trough plants). water than that required by the 2020 RPS. A closer analysis of the breakdown Freshwater Required for Energy Generation in California of water use for each of the different 2020, Water- energy sources within these two scenarios 2020, Fossil Fuel- Efficient Primary 2005 2020, RPS Based Energy Mix Energy Mix reveals a large proportional contribution 350 of geothermal and coal. While these two ) 3 300 primary energy sources constitute less than 250 a quarter of the generation capacity of the 2020 RPS and fossil fuel based scenarios, 200 they account for almost 90 percent of the 150 freshwater requirements of these scenarios. 100

Volume (Million m 50 Thus, altering the generation and cooling 0 technologies or primary energy sources WC WCCW WC can decrease freshwater withdrawals 55% fossil fuels 35% fossil fuels 64% fossil fuels 20% fossil fuels and consumption significantly below the 5% renewables 28% renewables 4% renewables 50% renewables 34% hydro & nuclear 27% hydro & nuclear 27% hydro & nuclear 30% hydro & nuclear 2020 RPS-based projected energy mix. 6% geothermal 10% geothermal 5% geothermal 0% geothermal Future water requirements for electrical generation can be reduced, not only below future projections, but even below current ENERGY water requirements. By incorporating PORTFOLIO technologies such as dry cooling and coal gasification into the RPS 2020 scenario, California’s projected annual freshwater Coal Geothermal Oil/Gas Solar Wind Bioenergy Nuclear Hydropower withdrawal and consumption requirements Average water required (W = withdrawals, C = consumption) for electricity generated in 2005 and decrease by 66 percent. By relying on more for three future (2020) scenarios. Although nuclear and hydropower are included in the portfolios water-efficient primary energy sources such (assumes existing infrastructure will continue to be utilized), they are not considered in the water requirements totals because California’s nuclear plants are seawater cooled and water use by as solar photovoltaic, wind, and waste- hydroelectric facilities counts all water flowing through turbines, a very different metric than other see California’s Nexus, page 30 water requirements for generation.

September/October 2007 • Southwest Hydrology • 21 California’s Nexus, continued from page 21 based bioenergy, we project California’s The Energy Intensity of Water Supplies water withdrawals and consumption to R. C. Wilkinson – University of California at Santa Barbara decrease even further, up to 90 percent. The total energy embedded in a unit of A spreadsheet-based computer model water used in a particular place varies (available from the author) calculates both To make the collected data available in with location, source, and use. The energy individual and cumulative energy inputs intensity of water is the total amount of of each process in the water system to a more user-friendly manner, a Web- energy, calculated on a whole-system determine its energy intensity. The table based tool was created to calculate basis, required for the use of a given below illustrates the range of energy the estimated water requirements amount of water in a specific location. All intensities for various water systems in (both withdrawn and consumed) of steps in the process, starting with initial Southern California. extraction from a natural source through a given portfolio (see sidebar). The energy intensity calculator is available for no conveyance, treatment, distribution, end- charge from the author. Contact R.C. Wilkinson at uses, waste collection, treatment, and [email protected]. A Clear Benefit to Water Efficiency discharge are included. in Energy Planning There are several key conclusions of this Efficiency analysis. First, a water-efficient energy Reuse (IEUA) RECYCLED WATER portfolio demands the right mix of primary Reuse (WBMWD) energy sources, conversion technologies, Reuse (Osmosis) and cooling technologies. Utilities should Groundwater (WBMWD) therefore focus on increasing investment GROUNDWATER in water-efficient electricity generation Groundwater (IEUA) such as solar photovoltaics, wind Groundwater (Ion Exchange) power, and coal gasification systems. Groundwater (RO)

CO River (MWD) Second, policies that encourage SURFACE WATER conservation of water can greatly reduce State Water Project (West Branch) future water requirements. For example, State Water Project (Coastal Branch) issuing conservation credits to energy State Water Project (East Branch) utilities that implement programs to reduce State Water Project (Crafton Hill) water use will help reduce both water and State Water Project (Cherry Valley) electricity consumption. Integration of Ocean Desal (West Basin) water and energy infrastructure planning SEA WATER also offers several distinct benefits. Co- Ocean Desal locating wastewater treatment facilities 0 1000 2000 3000 4000 5000 6000 and power plants facilitates the increased kWh/acre-foot use of reclaimed water in power plants, IEUA — Inland Empire Utilities Agency; MWD — Metropolitan Water District; reducing potable water consumption RO — Reverse Osmosis; WBMWD — West Basin Municipal Water District and providing a reliable water supply. Energy intensity of selected water supply sources in Southern California.

Finally, many research gaps still exist. This transition to alternative sources of As freshwater resources will likely A thorough life-cycle assessment of electricity must be accomplished, however, become more constrained in the future electricity generation, including water in a manner that will not compromise the and may limit electricity generation, use in facility construction, is needed to reliability of our energy supplies. In addition water efficiency must be considered in understand the full water requirements to the impacts of electricity generation on energy planning. This analysis provides of electricity generation. Additionally, water resources, we must consider other a tool to support integrated planning as water-efficient energy portfolios environmental impacts. For example, between energy and water utilities, are developed, the feasibility must be covering the deserts of California with solar and to help government agencies determined, assessing both the availability panels may reduce pollution and conserve integrate water considerations into of energy resources and patterns of demand. water, but may have significant impacts to planning for future energy supplies. regional biodiversity and ecosystems through Contact: Dana Larson at [email protected] Several issues must be considered in the habitat loss. Finally, impacts on water integration of energy and water planning. resources may be region-specific. As we see First, relying on water-efficient renewable in the bioenergy sector, the production of Reference sources of energy decreases water use and dedicated energy crops may be limited in Dennen, A., D. Larson, C. Lee, J. Lee, and S. Tellinghuisen, 2007. California’s Energy-Water Nexus: may decrease greenhouse gas emissions the arid Southwest, but may be more viable Water Use in Electricity Generation. Report to be and provide greater political security. in wetter climates of the United States. published at University of California at Santa Barbara.

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