Yesterday afternoon, the Union of Concerned Scientists released a study that suggested that thermoelectric power plants were contributing to stress on the nation's supply of fresh water.
For readers of NEI Nuclear Notes, this issue isn't exactly new. Back in 2006, we needed to push out some clarifying information (click here and here) in the wake of the drought that struck Europe. Back then, the angle reporters would take targeted nuclear energy in isolation (speaking of reporters, see this from NEI's Steve Kerekes), despite the fact that any steam cycle power plant has to deal with the same issues. At the time we pointed out that data from the U.S. Geological Service showed that the largest use of freshwater in the country was not electric power generation, but rather crop irrigation.
NEI's Bill Skaff wrote the following response to the UCS study.
Responsible environmental management must begin with a recognition of the water-energy nexus—large-scale electricity generation and large-scale usable water production are interdependent. We cannot have one without the other. Power plants require water for cooling, and water utilities require electricity for filtration, purification, and pumping to deliver usable water. In fact, nationwide, about 80 percent of municipal water processing and distribution costs are for electricity.iHere's hoping that provides some useful context when it comes to domestic use of freshwater. Then again, something tells me that we'll probably be revisiting this story over and over again in the coming years. For more information, see this page at NEI.org.
According to USGS, residential consumption of freshwater—at 6.7 percent of U.S. total water consumption—is more than double the consumption of freshwater for electric power generation, at 3.3 percent.ii A typical nuclear plant supplies 740,000 homes with all of the electricity they use while consuming 13 to 23 gallons of water per day per household. By comparison, the average U.S. household of three people consumes about 94 gallons of water per day for indoor and outdoor activities.iii
Power plants may withdraw almost as much water as farms for irrigation, but 98 percent of the water withdrawn by the electric power sector is returned to lakes and rivers, available for other uses. Since only 20 percent of irrigation water is returned, irrigation is the largest consumer of water resources.iv Power plants observe the temperature limit of their discharge water as set by the state regulatory authority, who determines the temperature that is safe for fish and plant life.
Numerous scientific studies of power plants around the country—reviewed by state permitting authorities—demonstrate that once-through cooling systems have no adverse impact on aquatic life populations.v This is because the miniscule number of fish lost to the cooling system, when compared to the overall population, is readily replaced by prolific reproduction.vi
Cooling towers consume twice as much water as once-through cooling systems.vii In light of climate change modeling that indicates freshwater constraints, how can cooling towers nationwide be a sustainable choice of cooling system?
Wind and solar energy use very little water, but their electricity output is variable—wind changes speed and direction, clouds block the sun—and intermittent—the wind doesn’t always blow and the sun shine. An electricity grid can only balance a limited amount of these electricity shortfalls, limiting how much renewable energy can be accommodated by a grid before it becomes unstable and black outs occur. Moreover, the variable, intermittent output of these renewables is usually balanced by fossil plants, which emit carbon dioxide and air pollutants.
The electricity grid requires steady, reliable baseload electricity—the output of nuclear and fossil plants. Nuclear power plant water use is comparable to coal plants. Natural gas uses less water,viii but produces half as much carbon dioxide as a coal plant as well as nitrous oxide, which contributes to ground level ozone formation, a cause of respiratory ailments. By contrast, nuclear power plants produce no greenhouse gases or air pollutants during operations.
Sustainable development will require electricity for quality of life and a mix of energy sources to generate that electricity—renewable, nuclear, and fossil. We must balance all environmental, social, and economic factors and make trade-offs when considering what energy source or cooling system to deploy at each of our diverse ecosystems around the country.
i EPRI, Water & Sustainability, Vol. 4 U.S. Electricity Consumption for Water Supply & Treatment, 2002, p. 1-2.
ii U.S. Geological Survey (Wayne B. Solley, et al.), Estimated Use of Water in the United States in 1995, 1998, pp. 6, 48-9, 40-1, 36-7, 28-9, 44-5, and 32-3. Percentages are derived from the individual sector data tables rather than the summary percentage chart (Figure 7) on p. 19. The USGS 1995 study is the most recent to include both consumption and withdrawal data.
iii This calculation assumes a 1,000 megawatt nuclear plant operating at 90 percent capacity factor per year, the industry average of the time that a plant is actually operating compared to its operating 100 percent of the time. Average U.S. household electricity consumption is from EIA, Survey of Residential End-Use Electricity Consumption, 2001. Nuclear plant water consumption per megawatt/hour is from EPRI, Water & Sustainability, Vol. 3 U.S. Water Consumption for Power Production, 2002, p. viii. Residential water consumption per person is from U.S. Geological Survey, Estimated Use of Water in the United States in 1995, 1998, p. 24. Number of persons in an average U.S. household is from U.S. Census Bureau, Current Population Reports; reports consulted were from 1995, 2003, and 2006.
iv U.S. Geological Survey (Wayne B. Solley, et al.), Estimated Use of Water in the United States in 1995, 1998, pp. 48-9, 24-5, and 32-3.
v Among the studies submitted for NPDES permit renewal: Virginia Power, Impingement and Entrainment Studies for North Anna Power Station, 1978-1983, prepared by the Water Quality Department, Richmond, Virginia, May 1985. The study’s results are presented in Dominion, North Anna Early Site Permit Application, Revision 9, September 2006, p. 3-5-54. PSEG, Salem Generating Station NJPDES Permit Renewal Application, February 1, 2006, Section 5, Adverse Environmental Impact, p. 159. LWB Environmental Services, Inc. (L.W. Barnthouse), AKRF, Inc. (D. G. Heimbuch), Van Winkle Environmental Consulting (W. Van Winkle), and ASA Analysis & Communications, Inc. (J. Young), Entrainment and Impingement at IP2 and IP3: A Biological Impact Assessment, January 2008, p. 79. Carolina Power & Light, Environmental Services Section, Brunswick Steam Electric Plant 1993 Biological Monitoring Report, March 1994, p. viii. ASA Analysis & Communication, Inc., Impingement Mortality Characterization Report, 2006-2007 [for Oconee Nuclear Station], May 2008. p. ES-2. In addition, see Electric Power Research Institute, Ohio River Research Program: Impingement Mortality Characterization Study at 15 Power Stations, June 2009, pp. v-vi.
vi For a discussion of population dynamics, see National Research Council, Commission on Life Sciences, Committee on the Applications of Ecological Theory to Environmental Problems, Ecological Knowledge and Environmental Problem-Solving: Concepts and Case Studies (Washington, D.C.: National Academy Press, 1986), pp. 28-35.
vii National Renewable Energy Laboratory, A Review of Operational Water Consumption and Withdrawal Factors for Electricity Generating Technologies, March 2011, p. 6.
viii EPRI, Water & Sustainability, Vol. 3 U.S. Water Consumption for Power Production, 2002, p. viii. National Energy Technology Laboratory (G. J. Stiegel, J. R. Longanbach, M. D. Rutkowski, M. G. Klett, N. J. Kuehn, R. L. Schoff, V. Vaysman, J. S. White), Power Plant Water Usage and Loss Study, August 2005, revised May 2007, p. xiii.