Natural gas saves water, reduces drought vulnerability
To study the drought resilience of Texas power plants, Scanlon and her colleagues collected water use data for all 423 of the state’s power plants from the Energy Information Administration and from state agencies including the Texas Commission on Environmental Quality and the Texas Water Development Board, as well as other data.
Since the 1990s, the primary type of power plant built in Texas has been the natural gas combined cycle (NGCC) plant with cooling towers, which uses fuel and cooling water more efficiently than older steam turbine technologies. About a third of Texas power plants are NGCC. NGCC plants consume about a third as much water as coal steam turbine (CST) plants.
The other major type of natural gas plant in the state is a natural gas combustion turbine (NGCT) plant. NGCT plants can also help reduce the state’s water consumption for electricity generation by providing “peaking power” to support expansion of wind energy. Wind turbines don’t require water for cooling; yet wind doesn’t always blow when you need electricity. NGCT generators can be brought online in a matter of seconds to smooth out swings in electricity demand. By combining NGCT generation with wind generation, total water use can be lowered even further compared with coal-fired power generation.
The release notes that the study focused exclusively on Texas, but the authors believe the results should be applicable to other regions of the United States, where water consumption rates for the key technologies evaluated — hydraulic fracturing, NGCC plants with cooling towers and traditional coal steam turbine plants — are generally the same.
The Electric Reliability Council of Texas, manager of the state’s electricity grid, projects that if current market conditions continue through 2029, 65 percent of new power generation in the state will come from NGCC plants and 35 percent from natural gas combustion turbine plants, which use no water for cooling, but are less energy efficient than NGCC plants.
“Statewide, we’re on track to continue reducing our water intensity of electricity generation,” says Scanlon.
Hydraulic fracturing accounts for less than 1 percent of the water consumed in Texas. In some areas where its use is heavily concentrated, however, it strains local water supplies, as documented in a 2011 study by Jean-Philippe Nicot of the Bureau of Economic Geology. Because natural gas is often used far from where it is originally produced, water savings from shifting to natural gas for electricity generation might not benefit the areas that use more water for hydraulic fracturing.
Scanlon’s co-authors at the Bureau of Economic Geology are Ian Duncan, research scientist, and Robert Reedy, research scientist associate. The bureau is a research unit in the Jackson School of Geosciences at the University of Texas at Austin.
The Jackson School helped fund the research along with the State of Texas Advanced Resource Recovery (STARR) program, a state-funded program managed by the Bureau of Economic Geology.
— Read more in Bridget R. Scanlon et al., “Drought and the water–energy nexus in Texas,” Environmental Research Letters 8, no. 4 (20 December 2013)
