By Brian K. Schimmoller,
For the better part of its history, the power industry has taken water for granted. Where makeup water was needed for boiler and cooling systems, securing water rights from river, groundwater, or lake sources was relatively easy. That is no longer the case. Water issues are becoming a hot-button political issue, with disputes as bitterly contentious as any waged in Washington, D.C. or state capitals.
“The average citizen is becoming much more aware of water-related issues, and the power industry will need to adjust to whatever set of rules and regulations emerge from this emerging activism,” says Willard Bowers, Vice President of Environmental Affairs with Alabama Power Co. Bowers points to efforts by Georgia, Florida and Alabama to negotiate a water compact for the Chattahoochee River Basin that would regulate water allocation rights. Negotiations among the interested parties have broken down, highlighting the contentiousness associated with water issues in modern America.
One power plant up to the tip of its stack in water-related problems is the Mohave Generating Station in Laughlin, Nev., co-owned by Southern California Edison, Nevada Power, Salt River Project and the Los Angeles Department of Water and Power. As part of a 1999 consent decree with various environmental groups, Mohave is under court order to install additional emissions control equipment by January 1, 2006 to reduce haze over the Grand Canyon. Design and engineering work related to $1 billion in environmental and life-extension upgrade projects has been delayed – primarily due to unresolved coal and water issues – so a temporary, possibly permanent, plant shutdown is likely in late 2005.
Significantly complicating the situation is the fact that the 4,000 acre-feet of water required to slurry and transport the coal from the Black Mesa mine in northern Arizona to Mohave may soon be off-limits. The Hopi and Navajo tribes have clearly stated that the “N” aquifer, which currently supplies the slurry water, plays a central role in tribal life, culture and religion, and will not be available after 2005.
Mohave estimates its drawdown of the “N” aquifer at one-tenth of one percent per year, and blames recent water shortages on the drought rather than the power plant. The plant’s owners have looked elsewhere for slurry water, including Lake Powell and the Colorado River, but these sources have fatal flaws in one respect or another, according to Brian Katz, Manager of Generation Business Planning and Strategy for Southern California Edison. The “C” aquifer in southern Arizona is now under investigation, but this source is 120 miles from the mine site and the mine is 273 miles from the power plant. Approximately 28 months will be needed to complete a water study and environmental impact analysis on the effects of drawing water from the “C” aquifer, putting the operational status of Mohave beyond 2005 in even greater peril.
The political web is quite tangled. While the Native American tribes are eager to protect their water supply, they are just as eager to protect the economic benefits Mohave provides, estimated at $85 million a year for the Navajo and $20 million for the Hopi. Although the tribes could potentially press for an extension in the name of “economic damage,” such an extension is unlikely in light of the political capital expended to-date to shut off access to the “N” aquifer.
The importance of water is also manifesting itself in other plant design and operational issues. Conceivably, water sensitivities could compel permitting and regulatory agencies to require dry ash handling rather than wet ash handling, or dry scrubbers rather than wet scrubbers, according to Bowers. Air cooling is also gaining popularity around the country, and not just in arid western locales. Developers of several eastern gas-turbine power plants have had to include expensive air-cooled condensers to accommodate local and regional concerns about water availability and use.
Even at combined-cycle power plants using air-cooled condensers and recovering blowdown water, water consumption amounts to about 190 gpm, according to Phil Deen, Thermal Cycle Engineering Manager with Siemens Westinghouse. Driving that consumption to zero would be a major accomplishment. Together with the Energy & Environmental Research Center, Siemens Westinghouse is developing a liquid desiccant-based technology for removing water vapor from combustion flue gases. The process, called WETEX (Water Extraction from Turbine EXhaust), is being investigated under a two-year contract with the Department of Energy.
Based on preliminary research and engineering analysis, Deen believes recovering 240 gpm of water vapor from one stack of a 2×1 F-class combined-cycle facility would be feasible, eliminating the need for external water makeup. Various desiccants are available, including lithium chloride, ethylene glycol, and propylene glycol, but lithium bromide is the leading candidate because of its well-known desiccant properties, its wide availability, its moderate cost, and its extensive use in absorption chillers.
WETEX is a long way from commercialization. The partial-scale prototype will not be ready until 2005, and many questions will need to be answered regarding efficiency, scalability, desiccant degradation, capital cost, etc. Deen estimates the operating costs at $1.50-$4.00/thousand gallons, which includes the additional energy costs incurred, desiccant makeup costs, and amortized capital costs. Although a fairly wide range, these costs are comparable to those associated with producing demineralized water.
The power industry is experiencing an evolutionary path with respect to water issues similar to the one it has experienced with airborne emissions. Federal and state regulatory bodies continue to tighten the screws, complicating power plant siting, design and operation. In most states, regulatory language currently permits water use as long as no harm is done to others, according to Bowers. The definition of harm, however, is open to debate, which means that the same language could be used to require water conservation or water curtailment when permitting new plants or operating existing plants. Plant owners and operators, therefore, would be wise to positions themselves as devoted stewards of water resources.
Bowers summarizes the building water debate in sober terms: “People have fought wars over water.” Let’s hope it doesn’t get to that, but it doesn’t take much to hear the drums of war beating down the river.