Greenwire, October 4, 2007

WATER WOES LOOM AS THIRSTY GENERATORS FACE CLIMATE CHANGE

By Katherine Ling, Greenwire reporter

U.S. power generators girding for possible mandatory curbs on greenhouse gas emissions may also find themselves facing another climate-related crisis: water shortages.

This past summer -- unusually hot and dry in many regions -- offered a preview.

As electricity demand surged to keep air conditioners whirring, power plants confronted shortages of cooling water that forced shutdowns and led to inefficient operations. And that problem is expected to worsen as climate change intensifies summer heat waves and droughts in already-arid areas.

Water is no longer an afterthought for power plant planners, said Bob Goldstein, the Electric Power Research Institute's senior technical executive for water and ecological systems. That wasn't the case so long ago when proximity to transmission lines and fuel dominated power companies' planning.

"After you chose what type of plant you were going to build and site it, then you went about getting the water," Goldstein said. "Now, you have to consider the water up front as you decide where you are going to build it."

Electric generators are facing growing competition for water from thirsty cities, sprawling farms and new environmental regulations aimed at protecting aquatic resources and recreational activities. "Power plants are the last group in the queue," said Tom Feeley, technology manager for the National Energy Technology Laboratory's (NETL) Innovations for Existing Plants Program.

If current trends continue, power plants will be withdrawing 7.3 billion gallons a day by 2030 -- equal to all U.S. water consumption a decade ago, according to a Department of Energy report.

Ironically, nuclear power plants -- touted by the nuclear industry and its supporters as the answer to global climate woes because reactors don't emit greenhouse gases -- need more freshwater to keep from overheating than other generators.

Thirsty reactors

The average reactor needs more than 830 gallons of freshwater per megawatt hour. All but about 3 percent of that is returned to the stream, but it returns much warmer, the Energy Department said in a report to Congress last year.

Nuclear plants' thirst proved a problem this August, when electricity demands set records across the country. Daily maximum temperature records were matched or broken every day for 11 consecutive days, from Aug. 7-17, according to the National Climatic Data Center at the National Oceanic Atmospheric Administration. Meanwhile, there were droughts in the West, Southwest and Southeast.

On Aug. 16, water temperatures in the Tennessee River hit 90 degrees Fahrenheit at Athens, Ala., forcing the partial shutdown of reactors at the Browns Ferry Nuclear Plant. One reactor was shut down, and the other two reactors had to reduce operations by 25 percent. Meanwhile, Memphis and Nashville were experiencing record power demands.

Illinois, Michigan and Minnesota have scaled back nuclear plant operations due to drought in the past two years, according to the Union of Concerned Scientists, an advocacy group.

Nuclear plants in France, Germany, Sweden and Spain experienced similar shutdowns because of water temperatures in 2006. And in 2003, France shut down a quarter of its 58 nuclear power plants during a heat wave, even after water-temperature regulations were softened to "guarantee the provision of electricity of the country," according to a government statement.

Power plants fueled by coal and natural gas also use plenty of cooling water. Coal plants use about 750 gallons a megawatt hour and natural gas more than 600 gallons a megawatt hour, according to the Electric Power Research Institute (EPRI), an independent power and energy research center supported by the electric industry.

Concerns about water demands have spurred opposition to power plants proposed recently in Virginia, Idaho, the Great Lakes region and Nevada.

Rising stakes

"We are using a resource that everybody needs," said Ed Legge, a spokesman for the Edison Electric Institute, an association that represents investor-owned utilities. "It is another one of the important environmental issues we are going to need to address from a supply standpoint and an environmental standpoint."

The U.S. thermoelectric industry withdraws 136 billion gallons of freshwater per year, about 40 percent the country's total intake. But power plants consume only about 3.3 billion gallons. By comparison, agriculture accounts for another 40 percent of total freshwater withdrawn and 84 percent of water consumption.

But every request to withdraw water is being more closely scrutinized now.

There is more competition for that water, with the U.S. population expected to increase by about 70 million over the next 25 years. And with more people, there will be more demands for water for drinking, recreation and resource protection.

At the same time, electricity suppliers are under pressure to build more power plants. U.S. demand for electricity is expected to grow by about 40 percent by 2030, the federal Energy Information Administration says.

The industry is currently pushing to build baseload power plants because of this increasing demand for electricity. Larger plants are mostly expected to be coal or nuclear, Legge said, while new plant construction in the 1990s was mainly smaller natural gas plants used to supplement power during peak demand times.

The demand for new power plants is greatest in regions where water supplies were strained by drought this summer -- the Southeast, Southwest, and West, Legge said.

So why not rely on renewable energy sources? Legge said it is not possible to provide the quantity or consistency of power that is needed. And, moreover, some renewable power sources also rely on taking in water.

While wind and solar photovoltaic technology use little or no water, concentrated solar uses more than 700 gallons of water per megawatt hour, according to EPRI. Concentrated solar technology uses reflective surfaces to concentrate rays on a container full of a fluid.

Geothermal is also a significant water user. A University of California, Santa Barbara, study of possible energy generation portfolios that could meet California's goal of getting 33 percent of its energy from renewable sources by 2020 found that geothermal, along with coal, accounted for less than 25 percent of generation but over 90 percent of water intake.

Next wave?

Industry and government are searching for technological fixes to water-energy crunch, according to interviews with engineers, and DOE and industry literature. NETL's Feeley and researchers at 10 other DOE laboratories have been analyzing the energy-water nexus for the past four years.

About 30 percent of current U.S. generating stations use a traditional, wet "open-loop cooling" system, according to DOE. The system draws water from an adjacent water body, runs it through the plant to condense the steam needed to power turbines and then returns what is left to the water source. But the large water intake and the high-temperature of the discharged water create problems for aquatic life.

Most plants built since the 1980s have been using "closed-loop cooling," which regulates temperature through evaporation in a cooling tower. Such plants withdraw 5 percent of the water used by open-loop systems, but most of what it withdraws evaporates. There is considerable research to find ways to recapture the water lost to evaporation in closed loop.

Researchers are testing a "dry cooling system" that uses air to cool power plants. But the system is expensive to install and is 2 percent less energy efficient, on average, than wet-cooling systems. A dry cooling chamber is capable of chilling steam only to match surrounding air temperature and becomes less efficient as outside temperature rises. In very hot weather, dry-cooling plants may lose as much as 25 percent efficiency, DOE said.

There is also a hybrid system that uses dry cooling most of the time, then switches to a wet system when the temperatures climb. Such systems are expensive and may be difficult to permit, experts say.

Other alternatives include having plants cool themselves with "nontraditional" water drawn from oil and gas production, coal mines, municipal wastewater or other so-called gray water. Some Pennsylvania power plants are starting to use mine water, Feeley said.

"At this point, it is difficult to pick winners," in water technology, Feeley said. "You can look at the water-energy issue on the national basis, but you also need to break it down on the regional basis," depending on temperature and water resources in each area.

But he added, "Through research and development we can reduce that capital cost, make materials cheaper and achieve a higher degree of heat transfer. There are improvements that can be made."

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