Duke Energy’s power plants, including five on the Catawba, accounted for all 10 of the state’s top registered water withdrawals last year.
Coal-fired and nuclear plants suck up nearly 3.9 billion gallons of the Catawba each day. Some of the water is heated to make steam that turns turbines. Some is used to cool that steam, condensing it back into water.
Most of the water eventually is dumped back into the Catawba, but 68 million gallons a day goes up in vapor. That’s about two-thirds as much water as Mecklenburg County households use.
When Duke and municipal water systems commissioned a water-supply plan to stretch the Catawba’s supplies, it showed Duke’s share of net withdrawals growing from 40 percent now to 43 percent by 2065. The public’s portion dropped from 50 percent to 47 percent.
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That balance matters because Duke, as it manages the river, seeks to profit from water that belongs to everybody. Power plants account for nearly half the water withdrawn in the U.S. each day, the U.S. Geological Survey estimates.
“One of the things we got questions about was, ‘Is Duke doing enough?’ ” at presentations of the plan, Charlotte Water director Barry Gullet said. “It came out early and it came out often.”
Catawba Riverkeeper Sam Perkins says Duke isn’t doing its share.
He said it’s disingenuous for the plan to consider fitting the lakes with massive covers to reduce evaporation, an option cited in a one-sentence analysis, but not explore alternative cooling-water technologies that could cut Duke’s water use.
“You certainly shouldn’t allow the biggest player in the process to give extra money and control the process,” Perkins said. Duke paid $200,000 of the water plan’s $850,000 cost.
Bill Holman, a former state environment secretary who served on the advisory panel, said the Catawba plan “struck the right balance” and will evolve over time.
Duke maintains it does its part. The company has invested more than $3 billion since 2007 in solar and wind energy, which don’t use water, and shifted to water-efficient power plants that burn natural gas. Company-wide water consumption dropped 18 percent between 2010 and 2014.
And under a drought-response plan adopted in 2006, Duke shuts down its hydroelectric plants to keep lake levels high.
“We take the first hit and the biggest hit with the hydro reductions,” said Jeff Lineberger, Duke’s director of water strategy and hydro licensing.
Reaching a critical level
Increasing competition for water has the U.S. power industry probing ways to use less.
“Twenty years ago it was a critical issue in the West,” said Kent Zammit, who oversees advanced cooling research for the industry-supported Electric Power Research Institute. “Now it’s a critical issue in most places.”
Duke’s McGuire nuclear plant on Lake Norman and its sister plant, Catawba on Lake Wylie, generate the same amount of electricity. They’re starkly different in their water use.
McGuire draws in nearly 20 times as much water from Lake Norman, an ample source, as Catawba does from Lake Wylie. But Catawba loses 45 percent more water as vapor.
The nuclear plants use fission to heat water into steam that spins turbines. The turbines power generators that then make electricity.
The difference is in their cooling technology. Water circulating inside McGuire cools steam, turning it back into water, and is discharged. At Catawba, cooling water releases its heat into the air and is then reused.
Federal rules say new power plants will have to use “wet” cooling systems like Catawba’s. Because they draw less water, fewer fish are sucked into the power plants. The tradeoff is that wet systems lose more water.
Cooling systems like Catawba’s makes most sense for a power plant that is water-efficient to begin with, such as those fueled by natural gas, said John Rogers, an energy analyst with the Union of Concerned Scientists.
Rogers said Duke could avoid the water issue by investing more in renewable energy.
“Solar panels require no water for generating electricity. Wind turbines don’t care if water levels get to record lows and water temperatures to record highs,” he said by e-mail. “And energy efficiency gets you even further away from the energy-water collision.”
Alternatives are in research, including hybrid technologies and dry cooling that uses no water.
Most have drawbacks: High costs, large energy needs or failure to perform well in the hot, humid Southeast. Some existing plants would have to be essentially rebuilt to accommodate new cooling systems.
Georgia Power, working with Duke and other utilities, is testing technology that could consume 50 percent less water and be retrofitted to existing power plants.
Duke calls the tests promising but cautions they are small in scale.
“Any new cooling technologies need to be proven to work cost-effectively at the plant scale in the Southeast before Duke Energy would consider applying them at one of its steam plants,” Lineberger said.
Catawba River water for energy, 2014
(million gallons a day)
Marshall Steam Station
McGuire Nuclear Station
Allen Steam Station
Catawba Nuclear Station
Source: Duke Energy