Drought is a serious vulnerability for the power sector, witnesses testified at a full committee hearing held last week in the Senate to assess the impacts of drought on the power and water sectors. Members of the panel invited by the Senate Committee on Energy and Natural Resources offered a number of possible solutions for federal agencies and power companies that could mitigate adverse effects from drought.
Drought affected 60% of the U.S. in 2012, and damages associated with drought last year exceeded $35 billion, said Committee Chair Sen. Ron Wyden (D-Ore.) as he opened the hearing. Water, a critical resource for generating electricity, must be sufficiently available, but also cool enough to allow power plants to run safely and efficiently, he said. "This means that climate change poses a double threat to some of these facilities, potentially threatening both water availability and sufficiently cool intake water."
Wyden outlined some recent examples of how drought affected the sector. In 2001, severe drought in California and the Pacific Northwest resulted in significantly reduced hydroelectric generation, causing tight electricity supplies and high prices throughout the West. During the summers of 2011 and 2010, the Tennessee Valley Authority had to curtail the output of its Browns Ferry nuclear reactors in Alabama because the temperature of the river water used for their cooling water became too warm. Last year, Dominion Power was forced to shut down one unit at its Millstone Nuclear Power Plant in Connecticut owing to warmer-than-average waters in August, while Exelon Corp. had to receive special permission from federal regulators to continue to operate its Braidwood reactors in Illinois when the units’ cooling water pond’s temperature reached 102F in July. In 2011, meanwhile, drought conditions in Texas forced the state’s grid operator to implement extreme conservation efforts, Wyden said.
Ranking committee member Sen. Lisa Murkowski (R-Alaska) echoed Sen. Wyden’s goals to identify all existing federal research authorities that could address the interdependency of energy and water.
“Drought Not New to Arid West”
As of April 7 this year, many states continued to experience "severe to exceptional drought," including Nebraska, Kansas, South Dakota, Texas, New Mexico, Colorado, Wyoming, Arizona, Nevada, Oklahoma, and California, testified Bureau of Reclamation Commissioner Michael Connor. But droughts and dry weather "are not new to the arid West," Connor noted. "The water infrastructure constructed by Reclamation and our partners in the West was built to mitigate for that reality. As the region continues to grow and experience changes in climate and the economy, we will continue to evaluate and plan for the impacts of drought."
Dr. Roger Pulwarty, director of the National Integrated Drought Information System (an agency associated with the Department of Commerce’s National Oceanic and Atmospheric Administration) reiterated Connor’s statement that drought is part of the American experience, pointing out that severe, long-lasting droughts had intermittently plagued the country. Weather conditions in 2012, however, were made distinct by the "persistence of the areas of dryness and warm temperatures, the magnitude of the extremes, and the large area they encompassed," he said. The deficit in rainfall over the Midwest in 2012 was –34.2 mm—a record that exceeded the historic –28.4 mm deficit observed in 1934.
A Number of Serious Vulnerabilities
As well as decreased power generation from hydropower and threatened cooling water supplies, drought also increased power costs, Pulwarty observed. Drought conditions may also cause extraordinary demand for electricity, leading to adverse effects if power generation fails to meet demand. And, it can also disrupt navigation and shipping of coal and other fuels, facility siting decisions, and inadvertently affect impacts to farmers due to necessary transfer of water rights to the energy sector.
"Energy companies are forced to use a variety of sources of information for their operations and planning, including in-house resources, private consultants, external drought management advisory group, and many of NOAA’s existing products and services," he said. "In some instances, however, these existing forecasts and other products might not be accurate enough to be used to make specific operational and management decisions. This is one area where improvements (i.e., seasonal drought forecasts) would be valuable."
Perhaps the nation would best benefit if it better understood which energy plants are susceptible to water shortages in drought-sensitive locations so that agencies could provide options to prevent or mitigate consequences in the short to long term, Pulwarty said. Other solutions include improved understanding of links between climate and hydrological processes, including aquifer recharge rates and groundwater movement, and a coordination among federal agencies regarding quality and use of climate and weather information at the energy-water interface, he said.
“Power Sector Responsible for Only 3% of National Water Consumption”
Dr. Michael Webber, an associate professor at the University of Texas at Austin’s Department of Mechanical Engineering and director of the Energy Institute, provided more startling statistics about just how reliant the power sector is on water. Cooling of power plants is responsible for 39% of non-consumptive freshwater use and is responsible for total withdrawals of nearly 200 billion gallons of water per day—but because most of that water is returned to its source, the power sector is responsible for only 3% of national water consumption, he claimed.
Citing data from 2011 (see page 3), he said nuclear plants with closed-loop cooling towers withdraw about 1 gallon/kWh (gal/kWh) and consume 0.7 gal/kWh, while open-loop plants withdraw 42.5 gal/kWh and consume 0.4 gal/kWh. Concentrated solar power plants with closed-loop cooling systems, in comparison, withdraw 0.8 gal/kWh and consume 0.8 gal/kWh. Coal plants come next: Closed-loop plants withdraw 0.5 gal/kWh and consume the same amount, while open-loop plants withdraw 35 gal/kWh and consume 0.3 gal/kWh.
Webber proposed several solutions to reduce the vulnerability of the power sector, calling for the installation or switching of fuel and conversion technologies to lower-consuming options. He also proposed installing or switching cooling technologies to lower-consuming options, and switching water sources (for example, to effluent from wastewater facilities or saline water). He noted, however, that "these technical solutions face some policy or cost hurdles today."
Sources: POWERnews, Senate Committee on Energy and Natural Resources
—Sonal Patel, Senior Writer (@POWERmagazine, @sonalcpatel)