Save Energy to Save Water

In a year when drought and water-use restrictions are in place in many areas, particularly the Rocky Mountain states, it makes sense to examine an often overlooked aspect of water efficiency—that of power production. It takes water to generate electricity in the United States—a lot of it, according to researchers at the National Renewable Energy Laboratory (NREL). “Most people don’t think about the amount of water evaporated at power plants to produce electricity,” says Paul Torcellini, Ph.D., P.E., of NREL. Torcellini and fellow NREL researchers Nicholas Long and Ron Judkoff collected data on consumptive use of water for power generation from the U.S. Geological Survey (USGS) and other sources and correlated that with power generation data. Their detailed findings will be published in a forthcoming NREL technical paper; a preliminary summary is presented here.

The vast majority of power plants in the U.S. consume water, either through evaporation in the cooling cycle of power generation (in thermoelectric power plants) or through evaporation of water impounded in reservoirs (in hydroelectric power plants).

Thermoelectric power plants—which can be powered by fossil fuels, nuclear power, or geothermal energy—account for 89% of total U.S. power production. These plants consume water primarily through evaporation, as excess heat is removed from the condenser. Of the total cooling water use by thermoelectric plants, 97.5% is recycled in closed-loop systems, but consumptive uses still account for 3.31 billion gallons per day (12.5 billion l/day) of water use, according to NREL. Water is also consumed in mining the fuels used to power thermoelectric power plants (this portion accounting for 8.7% of total water consumption).