Trade-off looms for arid US regions: water or power?
Water consumed by electric utilities could account for up to 60 percent of all nonfarm water used in the US by 2030.
The drive to build more power plants for a growing nation – as well as the push to use biofuels – is running smack into the limits of a fundamental resource: water.
Already, a power plant uses three times as much water to provide electricity to the average household than the household itself uses through showers, toilets, and the tap. The total water consumed by electric utilities accounts for 20 percent of all the nonfarm water consumed in the United States. By 2030, utilities could account for up to 60 percent of the nonfarm water, because they use water for cooling and to scrub pollutants.
This water-versus-energy challenge is likely to be most acute in fast-growing regions of the US, such as the Southeast and the arid Southwest. Assuming current climate conditions, continued growth in these regions could eventually require tighter restrictions on water use, on electricity use, or both during the hottest months, when demand for both skyrockets, researchers say. Factor in climate change and the projections look worse. This is prompting utilities to find ways to alleviate the squeeze.
Here in New Mexico, scientists and water managers are already wrestling with the issue. One of the state's main sources of electricity is the San Juan generating station. Its main source of cooling water is the Navajo Reservoir, which straddles the state's border with Colorado. Under today's climate conditions, a three-year drought might require users of the reservoir to cut their water consumption by 18 percent, according to preliminary research at the Los Alamos National Laboratory. But a three-year drought with an average temperature rise of 1 degree C (1.8 degrees F.) could mean a 65 percent reduction by the end of the third year.
"This isn't just the San Juan River basin we're talking about," says Andrew Wolfsberg, a hydrologist at the lab. If the US decides to develop oil shale deposits in southern Colorado, which is likely to be water-intensive, it will be difficult to keep oil shale development going, he adds.
A large-scale move to biofuels would be even more water-intensive, says Ronald Pate, a researcher at Sandia National Laboratory in Albuquerque.
Over the past five years, water availability and quality have become rallying points for opponents of new plants around the country, according to a December 2006 Department of Energy report on the issue. By some estimates, electric utilities plan to build 150 coal-fired generating stations in the US over the next 30 years.
"Utilities are beginning to recognize that water is becoming a greater permitting issue than air quality," says Thomas Feeley III, a technology manager at the US Department of Energy's National Energy Technology Laboratory in Pittsburgh.
The potential collision of water, energy, and climate is not limited to the US. "This is a big issue in other arid and semi-arid parts of the world," says Christopher Flavin, president of the Worldwatch Institute, a nonprofit environmental think tank in Washington. The challenge is especially acute in China and India. India already faces serious water shortages around the country, he says. And in China, he says, the central government is losing control over energy planning as local governments drive the push for more power plants. In the future, if climate forecasts are correct, the demand for thermoelectric power could continue to grow as mountain glaciers melt, reducing the amount of electricity hydroelectric dams downstream can generate.
In the US, utilities are exploring ways to cut water consumption at power plants or are looking for alternative water sources.
In West Virginia, for example, construction began in February on a 600-megawatt coal-fired plant that will pull its water from pools in the same mine that it's tapping for coal. Although the plant is a commercial facility, it also is a test bed for approaches to tapping mine pools, which are found throughout the region, notes Joseph Donovan, who heads the Hydrological Research Center at West Virginia University in Morgantown.
And at the San Juan generating station outside Farmington, N.M., the Public Service Company of New Mexico has been exploring a range of approaches to reducing the plant's water consumption, notes Timothy Jones, the utility's water resources manager. In June, the plant will test a new design for cooling towers that attempts to capture and recycle the cloud of condensation that towers give off. The plant already recycles water from 20 to 50 times before it's evaporated off or becomes so tainted that it needs to be hauled off for disposal. The plant also has looked into using water produced as a byproduct of oil and gas extraction in the region.
"It has a fabulous potential for power plants," he says. But today's water-treatment technologies are too expensive and don't have enough capacity to fit the need.
The plant also is using a hybrid cooling tower that uses water only when air temperatures rise too high; otherwise the plant uses air for cooling.
In the end, "there is no single silver bullet" for coping with the projected effects of global warming, Mr. Jones says. "Renewables will play an important role, but energy efficiency is the only way you can deal with it without environmental impacts."