With utilities already alarmed by looming federal regulations that could force construction of expensive cooling towers that would sharply increase water use, a report by the Energy Department’s Argonne National Laboratory warns that nearly 350 U.S. coal-fired power plants are vulnerable to potential water demand or supply conflicts over the next 20 years stemming from increased competition for dwindling water resources—particularly in the Southeast.

The Argonne report, Water Vulnerabilities for Existing Coal-Fired Power Plants, was released quietly in August by the DOE’s National Energy Technology Laboratory (NETL), which funded the study.

The report is part of a stream of NETL research aimed at analyzing water-related risks to coal-fired generation, and it comes as utilities are voicing growing anxiety about an impending Environmental Protection Agency (EPA) regulatory proposal that could require all new plants—and perhaps many existing units—to install cooling towers.

The EPA’s cooling tower rule is driven in large part by concerns that power plants’ traditional "once-through" cooling systems pose an unacceptable hazard to aquatic species. Such systems withdraw millions of gallons of water per day from rivers or lakes to cool steam generated by a plant and then return the heated water to the source. Such thermal discharges are blamed for killing millions of fish and other aquatic organisms each year.

Because cooling tower technology relies on evaporation to cool a plant’s steam, cooling towers consume much more water than once-through systems do, but they prevent the damage to aquatic systems that once-through systems cause.

The DOE report projects that while demand for water among all U.S. users over the period 2005 to 2030 will increase by 7%, demand from coal-fired power plants over the period will grow by 21%, driven largely by the assumption that most new coal plants built during the period will use wet recirculating cooling systems—or cooling towers—as a result of the EPA regulations.

The report noted that the sharp projected increase in coal-plant water use over the next two decades does not factor in the likelihood that many coal plants will add carbon capture and storage (CCS) technology to meet legislative or regulatory mandates to constrain U.S. carbon emissions. CCS technology can increase water consumption by 30% to 40%, the report noted.

At the same time, population growth in the Southeast and other regions of the country where water supplies already are under stress means that coal-fired generation in those regions will face significant competition for water, the report concluded.

"The high projected demand for water by power plants, which is expected to increase even further as carbon-capture equipment is installed, combined with decreasing freshwater supplies in many areas, suggests that certain coal-fired plants may be particularly vulnerable to potential water demand-supply conflicts," the report said. "If not addressed, these conflicts could limit power generation and lead to power disruptions or increased consumer costs."

The report analyzed NETL data for more than 500 coal plants with 18 indicators of water demand and supply, including frequency of rainfall, changes in stream flows, population growth, the intensity of water use in a given region, and other factors to develop a ranking of the relative vulnerability of each plant to supply-demand shortages.

The report identified 347 plants as potentially vulnerable to water shortages and found that 43 states have at least one vulnerable plant. About one-third of the vulnerable plants are located in the Southeast, which has experienced steady population growth in recent years—and also seen increasingly frequent and long-lasting droughts.

Four of the five states with the largest number of vulnerable plants are in the Southeast, led by North Carolina (24), Virginia (21), and South Carolina (19). Indiana, with 19 plants seen as vulnerable, and Georgia (18) rounded out the top five states. Other areas of concern are the Mid-Atlantic, Midwest, and the Southwest, the report said.

In North Carolina, seven of the 24 plants seen as vulnerable are owned by Duke Energy Corp., including the 2,240-MW Belews Creek Steam Station—Duke’s largest coal plant in the Carolinas—and the 2,090-MW Marshall Steam Station.

Duke has signaled that it will retire some 800 MW of generation in the next decade as part of the modernization of its Cliffside Unit, another plant seen by the report as vulnerable; the Cliffside project includes the addition of a second cooling tower at the site. Duke either is repowering or shutting down some of the smaller plants identified in the report.

Five of North Carolina’s vulnerable plants are owned by Progress Energy Corp., but Progress announced last year it will close four of these due to coming EPA air regulations that are expected to require sulfur dioxide scrubbers at the 40% of the fleet that lack scrubbers.

Roughly half (53%) of the 347 plants seen as vulnerable across the United States use once-through cooling systems, while the remaining 47% use recirculating systems. Of the vulnerable plants that use once-through systems, about 80% use freshwater, 10% use cooling ponds or canals, and about 10% use saline water.

The report said research already is under way at NETL to determine if "non-traditional" waters can substitute for some portion of freshwater used for cooling in existing power plants. The report defined "non-traditional" waters to include water from deep saline aquifers, coalbed methane fields, mine pools, oil and gas fields, and possibly "produced water" from shale gas extraction.

The report used mapping techniques to determine that about 157 vulnerable plants are located near at least one source of these non-traditional waters, with 122 plants near saline aquifers, 64 near shale gas plays, and 47 near mine pool water. Much of the northern and central Southeast, however, has no saline aquifers, few coal-bed mining sites or mine pools, and is far from oil and gas production areas.

—Chris Holly is a reporter for The Energy Daily, where this first appeared.