Power Plants Conserving Water

Why can’t power plants conserve more water- case study in North Carolina?

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.

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 Power plants account for nearly half the water withdrawn in the U.S. each day, the U.S. Geological Survey estimates.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.

Source: Charlotte Observer

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