Rooftop Solar Panels Currently Save Arizona More Than 750 Million Gallons of Water Annually

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1 Rooftop Solar Panels Currently Save Arizona More Than 750 Million Gallons of Water Annually By Herb Guenther Executive Summary Arizona s future renewable water supply is in serious jeopardy. The Colorado River is over appropriated, changing weather patterns threaten to reduce it up to 30 percent more and we are in the midst of a 15 year drought with no end in sight. While instate rivers provide an annual average of 1.2 million acre-feet (MAF) renewable water, that supply is also threatened by reductions due to drought and changing weather patterns. With Lakes Mead and Powell currently near record low water levels, the Secretary of Interior could declare a Colorado River shortage whereby Arizona could lose as much as 1/3 of its Central Arizona Project water. Those factors along with the expected increase in population will challenge future leaders to provide the necessary resources. Saving water will no longer be an option; it will be an absolute necessity. There is no one magic solution to securing our future water supplies. We should start with water saving measures that reduce our current water consumption. One method of saving water is rooftop photovoltaic panels. Arizona generates more than 95% of its power with thermal/hydro power plants. Thermal generation of electricity is only second to irrigated agriculture in the withdrawal of water. The question is how much water is consumed. Using median water consumption values based on fuel type and technology and the percentage of Arizona s total electrical energy represented, thermal/hydro power plants in Arizona use a weighted average of 685 gallons per megawatt-hour (MWh) of energy generated. The median amount of water consumption for photovoltaic (PV) rooftop panels is two gallons per MWh, which means that using rooftop PV for electricity generation can reduce water consumption per MWh by 99.68% 12,14. The average annual electricity consumption per household in Arizona is about 14 MWh 3. That would require approximately 9,590 gallons of water consumption per year using thermoelectric/hydro power versus 28 gallons for rooftop PV power, a savings of 9,562 gallons/year/household. The average rooftop installation of PV panels in Arizona is 7 kw 9. That system will generate MWh over 25 years, the estimated productive life of a standard PV system. The MWh of electricity would require 188,515 gallons of water using thermoelectric/hydro power, but 550 gallons for the PV power, a savings of 187,965 gallons of water per average rooftop installation over 25 years.

2 As of the end of June 2015, Arizona had 54,407 rooftop PV installations with a generation capacity MW 8. Currently rooftop PV solar makes up less than 1% of Arizona s total electricity, and saves the state more than 750 million gallons of water each year. If rooftop PV solar accounted for 20% of our electrical generation, the water savings would be in the realm of 47,267 acre feet (15,402,067,646 gallons) per year, more than enough to serve the annual water needs of more than 90,000 homes, or the entire population of Chandler, AZ 15,16,17. Utilizing the sun s free energy, rooftop photovoltaics save money and save water. If Arizona can continue to expand its use of low water use rooftop solar, we can add more certainty to our future water supplies. About the Author I have been involved in water issues in the Western United States for more than 43 years. Many of the comments in this document related to water are from personal experience. For more detail about my background, please see Appendix A. Available Water Water is the most essential natural resource on earth. Life cannot exist without it. There is a fixed amount of water on this planet. Water cannot be created or destroyed. It can only change physical form and location: water as a liquid, water as ice, water as a vapor as in humidity and clouds and water in the soil. Of all the Earth s water, 97.5 percent is salt and 2.5 percent is fresh. Of that fresh water, about 69 percent is locked in glacial ice and 30 percent bound in the soil, leaving under 1 percent (0.007 percent of the total water) readily accessible for human use 30. Historical Perspective on Water in the Southwest The Colorado River provides 65% of Arizona s renewable water supplies. Arizona, more than any other Colorado River Basin State, is in a critical position to lose necessary water supplies in the very near future for several reasons. We share the water from the Colorado River with six other Basin States, Wyoming, Colorado, Utah, New Mexico, Nevada, California and the nation of Mexico. Recent tree ring research has found that the Colorado River Compact of 1922 and the 1944 Treaty with Mexico over appropriated the Colorado River by as much as 4 million acre feet (MAF). For perspective, that equates to 1.3 quadrillion gallons, almost one seventh of Lake Mead s maximum capacity and enough to cover the state of Connecticut in over a foot of water 22.

3 The Colorado River Basin is currently experiencing a 15 year drought with no indication when it might end. The primary main stem reservoirs, Lake Mead and Lake Powell are currently near record low water levels. In 2007, the Basin States approved Interim Operating Guidelines (IOG) for the Colorado River after a long and arduous consultation process. The 2007 IOG included a provision for Arizona, California and Nevada to take shortages when Lake Mead water elevations reached critical levels. Under the Mexican Treaty Minute 319 adopted in 2014, Mexico agreed to voluntarily share in those shortages (a Minute to a Treaty is an amendment). In 1968, Arizona agreed to assume California s shortage responsibility in exchange for the necessary Congressional votes to gain passage of the Authorizing Legislation for the Central Arizona Project. Because of that, Arizona will take the brunt of any declared shortages in the Lower Basin as reflected in Table 1. Table 1 Lake Mead Elevation Arizona Reduction Nevada Reduction Mexico Reduction ,000 13,000 50, ,000 17,000 70, ,000 20, ,000 Colorado River shortage reductions in acre-feet. Source: Central Arizona Project Changing weather patterns are expected to further reduce runoff from the Colorado River watershed by 10 to 30 percent by ,19.20,. In-state rivers provide additional renewable supplies. Water from the Salt, Verde, Gila and Agua Fria Rivers contribute an annual average 1.2 MAF. However, just like the Colorado River, that supply is subject to reductions from extended drought and changing weather patterns. Legal factors also threaten the use of Arizona s in-state river systems. Ongoing legal proceedings, the General Stream Adjudications on the Gila and Little Colorado Rivers, involve establishing the rights and priorities to all claims for water within those systems. Both adjudications have been in progress for decades and no end is in sight. They are extremely complicated proceedings involving 71,000 square miles of land and almost 98,000 claims 4. During the many years representing Arizona, I was immersed in Colorado River issues dealing with the U.S. Department of Interior and the six other Colorado Basin States. The one common theme in those years was How to conserve and/or augment the available water supplies. Augmentation considerations included importation from other water basins, weather modification (cloud seeding) and ocean water desalination. Importation was very expensive and wrought with political difficulties. Weather modification was both feasible and cost effective. Since 2007, Wyoming carried out a successful experimental program. Due to the success of that project and the low cost, Arizona, California, Utah, Colorado, Nevada, Wyoming and the U.S. Government are continuing to fund cloud seeding

4 pilot programs in the mountains that feed the Colorado River watershed. Future challenges will include shrinking snowsheds and finding suitable cloud systems and temperature regimes to make it snow. Ocean desalination was and still is a feasible alternative albeit very expensive and fraught with political implications. We are currently exploring the possibility of a joint desalination project with Mexico on the Pacific Ocean in the State of Baja California and on the Gulf of California in the State of Sonora. Arizona conservation measures implemented include subsidizing installation of low water use plumbing fixtures and appliances, banking unused surplus water and treated effluent in our groundwater aquifers, encouraging conversion of turf to low water use landscaping and establishing conservation tiered water rates that keep prices low for reasonable daily needs and cost disincentives for high water use. The preceding discussion demonstrates the fragile nature of Arizona s future water resources. Those factors along with the expected increase in population will challenge future leaders to provide the necessary resources to sustain that population while maintaining a quality lifestyle. Water will still be the most crucial resource. Saving water will no longer be an option; it will be an absolute necessity. There is no one magic solution to securing our future water supplies. We should start with water saving measures that reduce our current water consumption. The Water/Energy Nexus in Arizona Electricity Generation Arizona generates more than 95% of its power with thermal/hydro power plants. Thermal generation of electricity is only second to irrigated agriculture in the withdrawal of water. The real question is how much of that water is consumed. One method of saving water would be rooftop photovoltaic panels. There are numerous methods of generating thermal electricity. The method used to cool the generation process determines the amount of water consumed. Thermoelectric power plants boil water to create steam, which then spins turbines to generate electricity. The heat used to boil water can come from burning of fuel, from nuclear reactions, or directly from the sun or geothermal heat sources underground. Once steam has passed through a turbine, it must be cooled back into water before it can be reused to produce more electricity. Colder water cools the steam more effectively and allows more efficient electricity generation. Dry cooling avoids the use of water, but has some limiting factors. It is much more expensive, reduces efficiency, and in desert environments will not work during the hot summer days, unless converted to a hybrid system. Wet cooling is the predominate method utilized. There are three primary wet cooling options: once through water cooling, using cooling ponds to reuse the water and a recirculating cooling system where evaporative towers cool the water before it is reused. Arizona thermoelectric plants primarily use recirculating wet cooling. The median consumptive water use values are highlighted in Table 2.

5 Table 2 Median Water Use for Electric Power Generation in the U.S. by Fuel and 7, 31 Technology (Gal/MWh) Electricity Source Power Generation (on-site) Withdrawal Consumption Wet Recirculating Coal Once-through 35, Cooling Pond 11, Hydroelectric 440,000 9,000 Once-through 11, Natural Gas Recirculating Combined Cycle Dry 4 4 Cooling Pond 5, Wet Recirculating 1, Nuclear Once-through 37, Concentrated Solar Thermal Cooling Pond Wet Cooling Dry Cooling Dish Sterling 4 4 Geothermal Photovoltaic (PV) Solar 2 2 Biomass N/A N/A Wind <1 <1 Table3 ARIZONA 2015 Percentage of Net Electricity Generation 10 Natural Gas-Fired 20.5 % Coal-Fired 36.5 % Nuclear 31.5 % Hydroelectric 6.5 % Other Renewables 4.9 % Using the percentage figures in Table 3, I calculated the weighted average for water consumption in thermoelectric/hydro power plants in Arizona by multiplying the percentage times the highlighted consumption values in table 2 and adding those values together. The one exception is hydroelectric generation. In Arizona, hydroelectric power from the dams is third in priority following flood control and

6 water delivery. The main water consumption attributed to generation of hydroelectric power is evaporation from the surface of the impounding lake or reservoir. All reservoirs have multiple beneficial purposes that should share in those costs. The median number in table 2 (9,000 gallons) had already been reduced 50% from the NREL estimate 31, 10, 18, but I chose to reduce it an additional 80% because of the priority of hydroelectricity in our system. The weighted average for water consumption in thermoelectric/hydro power plants in Arizona is 685 gallons per MWh. The median amount of water consumption for Photovoltaic (PV) panels is 2 gallons per MWh, which means the difference between thermal/hydro and PV is a reduction of 99.68% 12,14. The water consumption for PV panels is for the occasional washing that may be required to remove dust or debris. Normally, local winds and rain are sufficient to keep the panels clean. The average annual electricity consumption per household in Arizona is about 14 MWh 3. That would require approximately 9,590 gallons of water consumption per year using thermoelectric/hydro power versus 28 gallons for rooftop PV power, a savings of 9,562 gallons/year/household. The average rooftop installation of PV panels in Arizona is 7 kw 9. A PV system will generate 1,669 kwh of electricity per year per nameplate kw capacity (assuming 14% losses for DC to AC conversion and other system losses) 1. A 7 kw installation will generate 11,683 kwh the first year (1669 kwh/kw x 7kW = 11,683 kwh). Assuming a ½ of 1% (0.005) annual degradation for 25 years 2, the system will generate 275,204 kwh, or MWh over that period. The estimated productive life of a standard PV system is 25 years. The MWh of electricity requires 188,515 gallons of water using thermoelectric/hydro power ( MWh x gallons/mwh), but 550 gallons for the PV power ( MWh x 2 gallons/mwh), a savings of 187,965 gallons of water per average rooftop installation per 25 years. As of the end of June 2015, Arizona had 54,407 rooftop PV installations with a generation capacity MW 8. Those installed systems generate approximately 1,124,238,400 kwh per year (673,600 kw x 1,669 kwh/kw) or 1,124,238.4 MWh, saving 767,854,827 gallons (1,124,238.4 MWh X gallons/mwh) or acre feet of water per year, based on our current mix of thermoelectric/hydro generation facilities. Conclusion Currently rooftop PV solar makes up less than 1% of Arizona s total electricity, and saves the state over 750 million gallons of water each year. If rooftop PV solar accounted for 20% of our electric portfolio, the water savings would be in the realm of 47,129 acre feet (15,357,096,949 gallons) per year, more than enough to serve the annual water needs of more than 90,000 homes, or the entire population of Chandler, AZ 15,16,17.

7 Utilizing the sun s free energy, rooftop photovoltaics save money and save water. If Arizona can continue to expand its use of low water use rooftop solar, we can add more certainty to our future water supplies. References Chandler, et al., Water and Watts Southeast Energy Opportunities, WRI Issue Briefs. April < Maulbetsch, J. S. and DiFilippo M. N., Cost and Value of Water Use at Combined- Cycle Power Plants, California Energy Commission, PIER Energy-Related Environmental Research. CEC Clean Air Task Force and The Land and Water Fund of the Rockies., The Last Straw: Water Use by Power Plants in the Arid West., Hewlett Foundation Energy Series. April < (7) Fthenakis, V. and Kim, H., Life-Cycle Uses of Water in U.S. Electricity Generation., Renewable and Sustainable Energy Reviews, 2010, vol. 14, issue 7, pages (1) NREL's PV Watts Calculator Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations. Gleick, Peter H., Cooley, H., Fulton, J., Water for Energy: Future Water Needs for Electricity in the Intermountain West, Pacific Institute. November Irfan, U., Solar, utility companies clash over changes to net metering, Climate Wire: Tuesday, September 3, 2013

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9 (33) Overpeck, J., and B. Udall Dry times ahead. Science 328(5986). (31) Wilson, W., Leipzig, T. and Griffiths-Sattenspiel, B. Burning Our Rivers: The Water Footprint of Electricity. A River Network Report; Rivers, Energy & Climate Program. (30) Infographic: 10 Things You Should Know About Water. Blue Circle (13) "Arizona Portion of the Upper Colorado River Basin Consumptive Uses and Losses Reports". U.S. Bureau of Reclamation Retrieved (11) SCIENCE - THE STATE OF THE UNIVERSE. MAY :11 PM Holthaus,E., Dry Heat, As Lake Mead hits record lows and water shortages loom, Arizona prepares for the worst. Gleick, P.H., Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press, New York), 1993, Igor Shiklomanov's chapter "World fresh water resources" (4) Eden, S., M. Ryder and M.A. Capehart, 2015, Closing the Water Demand- Supply Gap in Arizona, Arroyo, University of Arizona Water Resources Research Center, Tucson, AZ Closing-Demand-Supply-Gap Cost and Performance Baseline for Fossil Energy Plants Volume 1b: Bituminous Coal (IGCC) to Electricity Revision 2b Year Dollar Update, July 31, 2015, DOE/NETL-2015/1727 Yaquinto, G, Cost shifts: The inconvenient truth of rooftop solar., Guest Opinion, June 24, 2013., A commentary in the June 7 issue of the Arizona Capitol Times.

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11 review of existing literature. Environmental Research Letters. 7 doi: / /7/4/ (8) Greentech Media Research's Solar Market Insight Report Q Comparison of Alternate Cooling Technologies for California Power Plants: Economic, Environmental, and Other Tradeoffs, EPRI, Palo Alto, CA, and California Energy Commission, Sacramento, CA: (3) Household Energy Use in Arizona; A closer look at residential energy consumption, All data from EIA s 2009 Residential Energy Consumption Survey (9) Personal Communication, Kim Sanders, SUNRUN Craver, T.F., Jr., Raising Our Game, Distributed energy resources present opportunities and challenges for the electric utility industry. (12) (14) (15) Element.pdf (16) Source U.S. Census Bureau: State and County QuickFacts. Data derived from Population Estimates, American Community Survey, Census of Population and Housing, County Business Patterns, Economic Census, Survey of Business Owners, Building Permits, Census of Governments Last Revised: Wednesday, 14-Oct :11:05 EDT (17) Extrapolated from information in (15) and (16) (19) RISK MANAGEMENT STRATEGIES FOR THE UPPER COLORADO RIVER BASIN,

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13 About The Author Herbert R Guenther Troubled Waters Consulting LLC CEO April 2011 Present (4 years 6 months) PO Box 820, Show Low, AZ 85902Provide research, facilitation and mediation services on water, natural resources, environmental, agricultural issues and any other issue that requires resolution. Director Arizona Department of Water Resources February 2003 April 2011 (8 years 3 months) Elected State Senator Arizona State Senate January 1998 February 2003 (5 years 2 months) Phoenix, AZ Public Policy Specializing in Water Issues Wellton Mohawk Irrigation and Drainage District Special Assistant to the Manager April 1981 February 2003 (21 years 11 months) Wellton, AZ Responsible for environmental compliance, Congressional and Legislative relations, water management issues and flood control on lower 60 miles of the Gila River. Commissioner Arizona Game and Fish Commission January 1993 January 1998 (5 years 1 month) Phoenix, Arizona Area Represented Western Arizona Counties on the Commission that set policies, established rules and adjudicated violations of fish and wildlife matters for the State of Arizona. This position was a 5-year appointment by the Governor upon approval by the Senate.

14 Elected Representative Arizona House of Representatives January 1986 January 1993 (7 years 1 month) Phoenix, Arizona Area Public Policy Specializing in Water Issues United States Bureau of Reclamation Senior Biologist January 1971 March 1981 (10 years 3 months) Boulder City, NV Environmental Compliance, Natural Resource Inventories, Endangered Species and Water Management Recent Honor Lifetime Achievement Award in Public Policy; Significant achievements affecting public policy over his career. Arizona Capitol Times 2013 September 2013 Education Arizona State University; BS, Wildlife Biology; Glendale Community College; Associate of Arts (AA), Psychology; Washington High School Phoenix, AZ; High School Diploma;