The primary purpose of this project is to improve estimates of water withdrawal and consumption at the scale of the individual thermoelectric plant to better characterize the role of thermoelectric water use in the national water budget. As the largest water withdrawal category and a significant water consumer, thermoelectric water use has received increasing national attention due to drought and other environmental issues, and to the interconnection of using water to produce energy. Currently available thermoelectric water withdrawal and consumption data are inconsistent and incomplete, and coefficients used to estimate thermoelectric water use are contradictory. In response to this, the U.S. Geological Survey developed models to estimate the amount of water withdrawn and consumed at thermoelectric plants based on linked heat and water budgets, and to complement reported thermoelectric water withdrawals and consumption.
Water withdrawals and consumption were estimated based on heat- and water-budget models, including thermodynamically plausible ranges of minimum and maximum withdrawal and consumption, for 1,290 water-using thermoelectric plants in the U.S. for 2010. Plant characteristics and operations data reported to the U.S. Energy Information Administration (EIA) for 2010 were used to develop budgets of the major flows of heat and water at the level of individual plants. The heat- and water-budget models relied on classifying plants into electrical generation and cooling-system technology categories. Generation technology determines the share of fuel energy converted to waste heat (fuel heat not converted to electricity) that is transferred to cooling water in the condenser, whereas cooling-system type determines the modeling approach to estimate cooling water withdrawal and consumption. The generation-type categories included combustion steam, combined-cycle, nuclear, geothermal, and solar thermal. The cooling systems were broadly categorized as either wet cooling towers or surface-water cooling systems, and the surface-water cooling systems were further subdivided into once-through cooling systems and recirculating cooling ponds. Environmental data such as air temperatures, wind speed, and water temperatures were also used for model input to relate seasonal and regional affects on thermoelectric water use.
Plant-scale model estimates of withdrawal and consumption were summed to produce national and categorical totals and were compared to EIA-reported withdrawal and consumption data. Coefficients based on model estimates were developed for generation and cooling-type categories of plants and compared to coefficients calculated from EIA-reported net electrical generation and water use data. Total withdrawal reported to the EIA was about 24 percent higher than the modeled estimates, and total EIA-reported consumption was about 8 percent lower. Most thermoelectric generation in 2010 was not associated with thermodynamically plausible EIA-reported values of both withdrawal and consumption. Uncertainties in estimates reflect numerous factors, including contradictory definitions among different organizations, inconsistency in applying definitions, and data-quality problems and incompleteness in key databases. Differences among withdrawal and consumption coefficients based on EIA-reported water use for 2005 and 2010 and heat-budget model results for 2010 reveal opportunities for improving consistency and accuracy of reporting of water-use information at the plant scale.
