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Replacing Coal with Gas or Renewables Saves Billions of Gallons of Water:
"While most attention has been focused on the climate and air quality benefits of switching from coal, this new study shows that the transition to natural gas—and even more so, to renewable energy sources—has resulted in saving billions of gallons of water," said Avner Vengosh, professor of geochemistry and water quality at Duke's Nicholas School of the Environment.
[...] "For every megawatt of electricity produced using natural gas instead of coal, the amount of water withdrawn from local rivers and groundwater is reduced by 10,500 gallons, the equivalent of a 100-day water supply for a typical American household," said Andrew Kondash, a postdoctoral researcher at Duke, who led the study as part of his doctoral dissertation under Vengosh.
[...] If all coal-fired power plants are converted to natural gas, the annual water savings will reach 12,250 billion gallons—that's 260% of current annual U.S. industrial water use.
Although the magnitude of water use for coal mining and fracking is similar, cooling systems in natural gas power plants use much less water in general than those in coal plants. That can quickly add up to substantial savings, since 40% of all water use in the United States currently goes to cooling thermoelectric plants, Vengosh noted.
[...] Even further savings could be realized by switching to solar or wind energy. The new study shows that the water intensity of these renewable energy sources, as measured by water use per kilowatt of electricity, is only 1% to 2% of coal or natural gas's water intensity.
"Switching to solar or wind energy would eliminate much of the water withdrawals and water consumption for electricity generation in the U.S.," Vengosh said.
Quantification of the water-use reduction associated with the transition from coal to natural gas in the U.S. electricity sector, Environmental Research Letters (DOI: 10.1088/1748-9326/ab4d71)
(Score: 2) by RS3 on Wednesday October 23 2019, @01:10PM
Good points, and I'll augment: I'm much in favor of renewables, but it will be many years until there's enough implementation to eliminate coal, gas, nuclear, etc. I'm not sure of the costs for nuclear vs. equivalent size renewables. One of many problems for nuclear is the very long construction time, so it may be better to put the $ into renewables. And of course that's being done.
All that said, I'm not an ME (am EE) but studied thermodynamics and have some broad understanding of many technical things. I like your thinking re: gas turbine rather than steam turbine. Most power stations are built around huge gigawatt generators. I surmise it would be completely impractical to try to build a gigawatt gas turbine, and for whatever reason, water/steam is always the intermediary. You could build a plant with many gas turbines, and I think the idea is worth investigating. I'm not sure of the overall energy efficiency of many small gas turbines vs. 1 large steam turbine though... That would be a huge consideration.
Maybe 30 miles from me is a nuclear generation station situated next to a river. They do use the river for cooling water, and most is pumped back into the river. There is boating and swimming in said river, and I've water-skied, and thus been in the river, just downstream from the nuke. You could feel slightly warm currents here and there, but nothing worrying, etc. Recently a news article talked about some nukes in Europe which had to run at lower capacity due to excess river water warming. Point being- much of the heat goes into water bodies, and it's monitored and controlled. Yes, eventually it increases evaporation in rivers and oceans. But otherwise the river does not seem to suffer any ecological ill effects.
Also, I have a friend who used to work at the station, so I have some inside info. There are 2 large cooling towers, and some days they emit large vapor clouds, but often there's nothing obvious, because they use the river for cooling, and if they're adding too much warmth to the river, they crank up the cooling towers.
There is strong evidence and argument regarding water vapor, visible or not, being a huge contributor to atmospheric heating.