It’s a complicated time to be an electricity-generating company in the United States. Volatility in the natural gas market is forcing utility planners to rethink fueling options, and new emissions regulations are adding even more questions to their long-term forecasts. Now water is becoming a critical component in plant siting and relicensing, as well, and its importance likely will rise should current drought conditions continue.
A recent report by The River Network, a Portland, Ore.-based environmental group, helps illustrate why water is a concern. According to their study, “Burning Our Rivers: The Water Footprint of Electricity,” the U.S. Geological Survey has found that 53 percent of all fresh surface water withdrawn for human use in 2005 went to operate our electrical grid. And the report estimates that 42 gallons go into every kilowatt-hour (kWh) we use.
Figures such as these become especially important when, as in August 2012, lack of rain forced officials to list more than half the nation’s counties as natural disaster areas. As of mid-January, the National Climate Data Center reporterd that moderate to exceptional drought covered 34.4 percent of the contiguous United States. In some areas, power plant operators face opposition from municipalities and farmers as each group seeks to advance its own water needs.
“As water resources become maybe more scarce, then those competing demands become even more significant,” said Richard Breckenridge, a senior project manager with the Electric Power Research Institute (EPRI) focused on power-plant water issues. “We’re all competing for it, and we all need to use it as wisely as possible.”
There are concerns, not only about how much water generating plants consume, but also the quality of the water they return to the environment since these plants send most of the water they withdraw back into surrounding waterways. So-called “once-through cooling systems,” though becoming less common, often release water that can be 20 degrees warmer than its original temperature, which can be devastating to surrounding fish and plant life. And water that’s been used to wash sulfur and other pollutants out of airborne emissions may carry some of those pollutants into other waters.
“I think water right now is just seen as a risk factor, rather than as an input that has real value,” said Wendy Wilson, water and energy project director with The River Network and a co-author of the report. “The tradeoffs have to be made site by site, watershed by watershed.”
All thermoelectric generating stations—that heat steam to drive turbines, including coal, natural gas and nuclear plants—use significant quantities of water to produce electricity. Of these, nuclear and coal power plants top the list in both water withdrawal and consumption, according to The River Network study. A nuclear plant, according to an average weighted by the number of plants using different cooling technologies, withdraws 14,732 gallons per megawatt-hour (gal/MWh) and consumes 532 gal/MWh. A coal plant withdraws 15,514 gal/MWh and consumes 506 gal/MWh. By comparison, the latest generation of combined-cycle natural gas plants withdraws (by weighted average) 1,170 gal/MWh and consumes 95 gal/MWh.
Such figures put coal-plant owners in an especially tight bind. These stations still supply more of our electricity than any other fuel source—37 percent in 2012 (though dropping quickly), according to the U.S. Energy Information Administration. However, a combination of falling natural gas prices and new emissions regulations are leading generating companies to close coal plants in large numbers. Add water-use concerns to this mix, and the technology’s days seem even more numbered.
Electric utilities recognize that water use could have as big an effect as airborne emissions in the near future. In fact, engineering leader Black & Veatch found water supply to be second only to carbon emissions as a top environmental concern for utility leaders in its June 2012 report, “Strategic Directions in the U.S. Electric Industry.” In Texas, especially hard-hit by drought, water use tops that list. When concerns about water effluent are combined with water supply worries, the full range of water issues tops even carbon emissions.
Even more important in the conversation regarding new plant siting, water issues—including ground-water quality, effluent and a plant’s projected water requirements—take three of the top seven considerations in utility resource planning efforts. The U.S. Environmental Protection Agency (EPA) has proposed new regulations under Section 316(b) of the Clean Water Act governing the operations of cooling-water intake structures. The new standards, which the EPA hopes to finalize by June 2013, could require some plants that currently depend on once-through cooling to add a cooling tower and expense that operators of older plants might not be willing to pay.
“We see longer term water issues beginning to be a concern but not universally,” said Chris Vlahoplus, a partner with Raleigh, N.C.-based ScottMadden, a management consulting firm that focuses on energy industry issues. “The industry as a whole is beginning to awaken to the broader issue and only now beginning to get its arms around this bigger picture.”
And that big picture shifts, depending on where plants are—or potentially could be—sited. For nuclear-plant operators in the Northeast, such as Exelon (New Jersey’s Oyster Creek station) and Entergy (New York’s Indian Point station), returned-water temperature might be the primary issue. But for coal-plant owners, particularly any company operating a coal plant in drought-stricken Texas, water consumption is the critical concern.
“The severity of the issue depends upon the local conditions for the generating plants. This highlights the importance of having an understanding of the unique local situation for a utility’s assets,” Vlahoplus said.
In fact, drought-related, low water levels can have an almost immediate impact on a plant’s operations if states start limiting the amount of water that plant is allowed to withdraw. Lower cooling- or scrubbing-water supplies can force the plant to reduce its generating capacity. Hotter weather can create similar capacity reductions (or “derating,” a reduction from rated capacity). For example, 2012’s persistent Midwest heat wave raised the temperature of the Mississippi River, the cooling-water source for the Cordova, Ill.-based Quad Cities nuclear plant, which forced operator Exelon to pursue EPA variances for resulting higher water-discharge temperatures.
As Vlahoplus said, utilities are beginning to recognize the importance water will have in their future operations. For example, generation site owners are ramping up research, investigating new technologies that could help reduce their plants’ water “footprint.” Among these are two major efforts headed up by the EPRI.
The larger of these programs is taking place at Plant Bowen, owned and operated by Georgia Power, a Southern Co. subsidiary. This 3,500-megawatt (MW) plant in Cartersville, Ga., is the largest coal-fired generating station in the United States. Georgia Power and EPRI are launching the Water Research Center (WRC) there to look at a range of advanced technologies for operating cooling systems, scrubbers and carbon-capture systems.
“A lot of the research is completely applicable to all sorts of generation,” Breckenridge said. However, he added, wastewater treatment findings will be primarily focused on coal.
“The importance [can be judged] by the number of major utilities that have joined this effort already,” said Jeff Brehm, EPRI spokesperson. “They look at water as the new air.”
Since the project was announced, 13 additional utilities—including such major players as AEP, Duke, Edison International and Arizona Public Service—have joined Georgia Power in funding this research.
Reducing water use in cooling operations is one area of the WRC’s work that will be useful to a range of generating technologies. The systems supplying turbines with steam generally operate in a closed loop in which water loss is minimal. However, that loop has to incorporate a cooling cycle for the condensed steam before it is returned to the turbine area for reuse. In many cases, plants run that closed loop through cooler water within a cooling tower, which can lead to cooling-water evaporation and create wastewater that’s too warm for surrounding aquaculture on discharge. The WRC recently initiated an investigation into alternative cooling methods, including a hybrid approach combining a cooling tower and a Johnson Controls chiller system to supplement the cooling tower during cooler times of the year.
Among other targets, the WRC will work to quantify the energy required for such alternate cooling methods.
“Many times to recover water involves some form of energy,” Breckenridge said, adding that there’s a tradeoff in how much water you can save, compared with how much energy is expended.
For example, Breckenridge noted, dry cooling, which uses air instead of water to cool steam, can reduce total power plant water consumption significantly. However, this water savings comes with an efficiency penalty of 5 to 10 percent, meaning less electricity is produced per unit of fuel. There is hope the hybrid system WRC will investigate will be more water-efficient without an unacceptably high-efficiency penalty.
EPRI’s second major water initiative, Water Prism, is supporting the development of an evaluation tool to help balance the competing demands on a specific region’s water supply in an effort to improve overall water-management decisions. This software-based product is being developed to help run test scenarios on alternative water-use plans and is being tested in real-life applications in water-constrained regions of the southeastern United States.
And the EPRI isn’t alone in developing such analytical aids. ScottMadden’s Vlahoplus noted Regional Watershed Risk Analysis Platform developed by the Research Triangle Park, N.C.-based RTI International (RTI). Abbreviated “R-Wrap,” this package melds expertise in hydrology and geographic information systems to categorize water-supply vulnerability in specific regional watersheds. RTI’s researchers see water-use drawing increased scrutiny from state regulatory agencies that are just beginning to recognize just how limited their water supplies might actually be.
“States are putting in place much more rigorous water-withdrawal permitting,” said Bob Dykes, director of RTI’s Water and Ecosystems Management Center. “Utilities will face an increasingly [more] difficult process to withdraw water [than] they have in the past.”
About The Author
ROSS has covered building and energy technologies and electric-utility business issues for more than 25 years. Contact him at [email protected].