Aqua-Shock
Thirsty power plants tap nation’s water resources.
If you really want to save water, don’t just stop watering your lawn—also switch off your lights… and your computer, and your TV.
“You use more water powering your appliances than you actually use washing your clothes and dishes,” said CIRES Associate Director for Science Kristen Averyt.
Coal, natural gas, and nuclear plants, which generate the nation’s electricity, use a lot more water than one might realize, said Averyt. These power plants use water to create the steam that drives electricity-producing turbines but also use vast volumes of water for cooling. Currently, power plants in the U.S. pull about 350 billion gallons a day—more water than is withdrawn by agriculture and nearly four times as much water as municipalities, according to a study completed by Averyt and a team of researchers in 2011.
Averyt became interested in the water usage of power plants when she started investigating strategies to manage water in the Western states. In this region, the demands of a growing population and a
warming climate herald potential water scarcity in the future. But when Averyt looked at the actual figures for where the water was going, she found a paucity of data about what amount power plants use—all major users of water.
“Who is using water? Where is it going?” Averyt said. “How can we plan for the future when we can’t account for every drop now?” Averyt said. Without a good accounting, managing the nation’s water would prove problematic, she said.
In Arizona, for example, some power plants withdraw their water for cooling from groundwater, a source of unknown quantity. “Some power plants are drawing on a checking account where they don’t know the balance,” Averyt said. “We really don’t know how much is being used.”
To address the problem, Averyt, along with colleagues from the National Renewable Energy Laboratory, academic institutes, and the Union of Concerned Scientists, set out to inventory the nation’s water use. For each type of power
plant, NREL researchers estimated the water required to produce 1 kilowatt hour of energy. Then, once they had found out how much energy the power plant produced, the team could calculate the water the plant used.
The team published its findings in the 2011 report “Freshwater Use by U.S. Power Plants: Electricity’s Thirst for a Precious Resource.” The study determined that power plants are often using more, and occasionally using less, water than they are reporting.
The authors also concluded that in several places around the U.S., power plants’ thirst contributed to water stress—the increasing demand relative to the supply of the nation’s water resources. During the 2011 drought in Texas, for example, farmers, cities, and power plants competed for dwindling water supplies, and some power plants had to truck or pipe in water from remote sources to meet their cooling needs.
Unfortunately, droughts often coincide with heat waves, and with heat waves come increased electricity demands as people switch on their AC, Averyt said. “So, it is the perfect storm,” she said.
A growing population demands more water and more energy, and a warming climate spells diminished water supplies. “We may be looking at a face off between many different players over water, and energy is just one of those players,” Averyt said. “At some point water may become as precious a commodity to the U.S. as oil and gas.”
Her team is also using their report as a springboard for further investigation at a regional level—in particular, the arid Southwest.
Currently, the researchers are analyzing the demands on water resources in the Southwest and exactly how power plant usage feeds into the equation, Averyt said. Accounting for all the checks and balances will allow researchers to make accurate assessments about the portfolios of power sources and new technologies for a specific region.
Averyt is confident, however, that future work to understand the energy-water nexus will help improve water reliability. “In the future, it would be nice if we didn’t have to choose between switching on the power or taking a bath,” Averyt said.
