A recent study by researchers Bridget Scanlon, Ian Duncan and Robert C. Reedy of the Bureau of Economic Geology at the University of Texas-Austin found that the state of Texas consumed less water as a result of using natural gas-fired power plants than it would have had it generated the same amount of electricity using coal-fired plants – even after taking into account the water used in hydraulic fracturing to source the natural gas used to generate the power. The overall impact of using natural gas power plants in Texas could help to make the state less susceptible to drought, despite the use of water for hydraulic fracturing.
Texas generates more electricity annually than any other U.S. state and uses natural gas to generate about 45% of its electricity, while relying on coal for about 35%, with nuclear and wind each generating about 10%. During periods of drought, the study data indicated that electricity demand/generation increased by 6%, while water demanded for electricity generation increased by 9%. However the study also found that Texas would have used 32 billion gallons more in water in 2011 had all its natural gas-fired plants used coal.
Since the 1990s, most new power plants in Texas have relied on natural gas combined-cycle generators. Because natural gas combined-cycle plants have more efficient cooling towers, they experience significant water savings as compared to coal-fired plants. Some estimates suggest that combined-cycle natural gas plants use about one-third the water of coal steam turbine plants. Natural gas combustion turbines also can be used to produce off-peak power when wind turbines are unable to generate electricity, and this combination also uses less water than coal-fired power plants.
The reported water savings are after taking into account the significant quantities of water used to extract natural gas by means of hydraulic fracturing. According to some sources, hydraulic fracturing can use as much as 5 million gallons of water per well, though total water usage for hydraulic fracturing is about 1% of all water used in Texas each year. This usage can place stress on local water supplies in the areas where fracturing activity takes place, while the benefits of lower-cost electricity and more efficient generation are more often widespread. Nevertheless, water use information from all 423 of the state’s power plants was used in preparing the study, and the researchers concluded that 25 to 50 times more water is saved by switching a single power plant from coal to natural gas than is used in the hydraulic fracturing needed to fuel that plant. This study bodes well for the future of water use in Texas, as nearly two-thirds of new energy generation in Texas through 2030 likely will come from power sources that rely wholly or partly on natural gas.
Additional coverage from Science Daily can be found here, and the Houston Chronicle article, via the San Antonio Express-News, here. The story was also covered by eurekalert.org, here. The study was published by the University of Texas and announced by its blog here, and published on December 20, 2013 in the journal Environmental Research Letters.