Researchers at NETL and the University of Wyoming report that using brackish water — water that is not suitable for drinking or irrigation because it contains between 1,000 and 35,000 parts per million of dissolved solids — to cool power plants can reduce freshwater consumption by 94% to 100%.

The results of the study were reported in a paper published online by Nature Portfolio and available here. 

Thermoelectric power plants boil water to create steam, which then turns turbines that generate electricity. After the steam has passed through turbines, it must be cooled into water before it can be reused to produce more electricity. 

In the United States, 90% of electricity comes from thermoelectric power plants that require cooling. 

Nicholas Siefert, Ph.D., a research mechanical engineer at NETL, said power plants are a major source of water consumption in the United States.

“In 2015, fossil fuel power plants withdrew more than 100 billion gallons of water per day, most of which was used for cooling and nearly 100% of withdrawals currently comes from surface waters,” he explained. “As water resources become increasingly scarce, there is a growing need for power plants to reduce their water use. One way to reduce water use is to use brackish water for cooling.” 

The NETL-led study evaluated the technical, economic and environmental impacts of using brackish water for cooling at fossil fuel power plants. The study found that using brackish water for cooling can reduce freshwater consumption by up to 100%. However, it could also increase the cost of electricity by 9% to 11%.

Haibo Zhai, Ph.D., an associate professor and chair of engineering at the University of Wyoming and adjunct faculty in the Department of Engineering and Public Policy at Carnegie Mellon University was also a key researcher on the project. Zhai said that while the study showed use of brackish water for cooling at thermoelectric power plants is a viable option for reducing water use, it also identified challenges that need to be addressed, including the high cost of brackish water treatment and the disposal of concentrated brines.

“The cost of brackish water treatment is estimated to be $0.50 to $1.00 per gallon,” Siefert said. “This is significantly higher than the cost of freshwater, which is typically $0.02 to $0.05 per gallon. The high cost of brackish water treatment is due to the need to remove the dissolved solids from the water.” 

The study indicated that another challenge to the use of brackish water for cooling at thermoelectric power plants is the disposal of concentrated brines that are produced during brackish water treatment. Concentrated brines are very salty and can be harmful to the environment, but they also contain valuable and critical minerals.

“There are a variety of potential disposal and reuse options,” Siefert said. “Those include injection wells, evaporation ponds, salt mines, and resource recovery. Each option has its own environmental and economic impacts that we will be analyzing in future research.”

The new study concluded that those challenges need to be addressed before brackish water can be effectively used for cooling at fossil fuel power plants.

NETL is a U.S. Department of Energy national laboratory that drives innovation and Sdelivers technological solutions for an environmentally sustainable and prosperous energy future. By using its world-class talent and research facilities, NETL is ensuring affordable, abundant and reliable energy that drives a robust economy and national security, while developing technologies to manage carbon across the full life cycle, enabling environmental sustainability for all Americans.