July 6, 2011
| 
12
This year, residents of Austin, Texas celebrated their 4th of July with plenty of beer and BarBQ – but there were no fireworks over Lady Bird Lake as a burn ban prohibited even sparklers from being sold in the area. Texas has just moved through its driest 8-month period on record. The lack of rain, coupled with record-breaking spring heat waves, has created a reality where some Texas towns might not have enough water to last through the summer. While residents hope for a wet hurricane season to end the drought, they have found a way to conserve water to the tune of millions of gallons per day. By using the wind to offset fossil fuels for electricity generation, the Lone Star State has shown how going green can help when regions struggle to balance water supply and demand.
In the United States each of us use, on average, almost 36,000 gallons of water a year for activities like showering and flushing the toilet. This does not include our indirect water use for growing the food that we eat or for generating the electricity that keeps our lights on. In the face of a drought, these simultaneous demands can lead to struggles in determining where the water should go.
For every kilowatt-hour (kWh) of electricity generated in the United States, 2 gallons of water are consumed due to evaporation. This means that the average U.S. resident indirectly consumes more than 9,400 gallons of water per year to run the power plants that generate electricity for their home. When you include the number of gallons of water used (though not consumed – also called “pass-through” water use) to generate this electricity, this number jumps by an order of magnitude or more.
This water is used primarily to cool thermoelectric (for example – coal, natural gas, and nuclear) power plants. Heat is generated in these plants by combusting fossil fuels or using nuclear fission. This heat is then used to boil water to generate steam, which turns a turbine connected to a generator that produces electricity. Cooling is needed throughout this process, not only to protect the boilers where the steam is produced, but also to cool the hot water that exits the turbines before it is discharged into cooling ponds or other waterways. In the United States thermoelectric power plants consume, on average, 0.47 gallons of water for every kilowatt-hour (kWh) that they produce.
To supply the nation’s total electricity demand, thermoelectric power plants use more than 200 billion gallons of water for cooling – EVERY DAY. While the majority of this water can be reused at these facilities, approximately 5 billion of these 200 billion gallons will be lost through evaporation. Texas is responsible for 6%, or 12 billion gallons, of these water withdrawals for a daily consumption rate of 300,000 million gallons of water.
But, Texas has managed to decrease the amount of water needed to generate electricity in the state by using the wind to supply a portion of the state’s electricity needs. While we might typically think of Texas in terms of its rich oil and gas resources (good ol’ Texas Tea), the state also has extensive renewable electric energy resources including solar, wind and geothermal (the new Texas ‘E’). Over the past decade, the state’s renewable portfolio standard (RPS) has driven Texas to become the nation’s leader in wind generation. Today, Texas has more than 10,000 megawatts(MW) of wind capacity installed – more than the next three-largest wind generating states (Iowa, California, and Minnesota) combined.
Over the course of a year, these wind turbines supply around 7% of Texas’s electric power needs. They also save the state millions of gallons of water because wind turbines require virtually no water to generate electricity. Alternatively, hundreds of gallons of water would have been consumed if a megawatt-hour from wind power was instead generated using natural gas (223 gallons/MWh), coal (426 gallons/MWh) or nuclear (600 gallons/MWh) power.
This summer, amid the heat and extreme drought, Texas set a new record for wind generation. At 10:26pm on June 19, 2011, the Electric Reliability Company of Texas (ERCOT) recorded 7,355 megawatts (MW) from wind generation – the most “Wind-Watts” that had ever been generating power on the Texas grid. This wind power represented 14.58% of the 50,447 MW load at the time. It also represented a savings potential of more than 2.4 million gallons of water per hour compared to thermoelectric alternatives. And, this number is likely conservative, as it does not include water consumption at the state’s hydroelectric facilities.
Power generation in hydroelectric facilities uses water directly in order to spin turbines connected to generators to produce electricity. Water is pooled to create a “head” and is then allowed to flow through the dam using gravity, being released on the other side at a lower elevation. While we can argue over the amount of water used by these dams (versus for recreational activities on the lakes and rivers that they connect to), we can certainly say that the increased surface area of the dammed water way leads to increased evaporation rates. According to the United States Geological Survey, hydroelectric power plants consume 18 gallons of water for every kilowatt-hour that they produce – more than 30 times their thermoelectric power counterparts.
This year, along with most of the southern United States, Texans are faced with extreme drought and the growing concern of what will happen if rain doesn’t come soon. Through investments in wind power, they have conserved millions of gallons of water, helping them to bide their time until the rain falls again. For Texans, as described in Bob Dylan’s 1963 lyrics, one “answer is blowin’ in the wind” [1].
For a list of calculations used in the writing of this post, please go here.
[Photo of wind farm © Copyright alan souter and licensed for reuse under this Creative Commons Licence]
[Photo of W.A. Parish Power Plant and its cooling pond (Smithers Lake) © Copyright roy luck and licensed for reuse under this Creative Commons Licence]
[Photo of wind farm and oil derrick © Copyright Mary Christenberry Lott and used with permission]
About the Author: An engineer and researcher who works at the intersection of energy, environment, technology, and policy. Follow on Twitter @mclott.
12 CommentsAdd a Comment
You must log in or register as a ScientificAmerican.com member to submit a comment.
What Thomas Kuhn Really Thought about Scientific "Truth"
Crowdfunding for Research Dollars: A Cure for Science's Ills?
3 Science Questions to Ask U.S. Presidential Candidates
Aerial views of the Alberta tar sands show the beauty and mess of the whole process
Belieber or Thiever: Who came first, Bieber or this scientist?It’s not about tar sands – it’s about us
YES! Send me a free issue of Scientific American with no obligation to continue the subscription. If I like it, I will be billed for the one-year subscription.
Share
Email
Print
Excellent post. It sure is hot and dry down here in Austin. Although I’ll add I was glad to miss the fireworks this year since they launch them right next to the Town Lake Animal Shelter.
It’s amazing that Texas – not generally the state we think of as “green” – generates so much wind power.
Link to thisI bet all this water usage increases the humidity too, pushing air conditioning usage up in a vicious cycle.
Link to thisSheril – I agree on the Town Lake Animal Shelter. It makes me sad to hear about all of the spooked animals on 4th of July and New Years. Yay for happy animals (hopefully about to get new homes!)
iluvdubya – yes, there are a lot of vicious cycles out there, including in the energy world. water consumption (and resulting impacts) is just one of them. There was an interesting study that I remembering coming out of the UT Austin Chemical Engineering dept ~2008 that discusses how air emissions (including water vapor) travel once they are released from a power plant’s stacks. Where it goes, when does it “stick around”, etc. Thanks for the comment.
Link to thisI received a great comment via e-mail that I wanted to share regarding the 18 gal/kWh number for hydroelectric power water consumption that I used in this post. The commenter was surprised by how high this value was.
Their comment brings up an interesting point on how water use is allocated by the USGS and other organizations. In the case of hydroelectric power, 100% of the increase in evaporation from damming waterways (versus free-flowing rivers) is attributed to power generation – even though there are other reasons for building a dam (ex: flood control or agriculture)
Link to thisDoes the method of extraction (i.e. fracking) affect the natural gas value?
Link to this@iluvdubya – The U.S. natural gas market doesn’t differentiate between extraction methods (gas is gas – defined by a set of standards – regardless of the process used to get it out of the ground). But, the “value” of the natural gas sold in this market is certainly affected by the extraction process used, as well as the composition of the natural gas at the wellhead.
The cost of the extraction process (for example, hydraulic fracturing or “fracking”) will impact the profit margin on the gas when it is sold in the market, potentially affecting the economic viability of a well.
The composition of the natural gas at the wellhead also affects the “value” of the natural gas extracted. The natural gas that we use at our homes is mostly methane. But, the natural gas that comes out of a well has a lot of other stuff in it – for example water, propane, helium, and hydrogen sulfide (H2S). These things must be removed before the now “pipeline quality dry natural gas” is allowed into the pipeline system that transports natural gas to customers. More processing means more money, more energy and more waste, which affect the “value” of the natural gas.
Link to thisVery interesting post! I was shocked to see such a high number – 200 gallons used every day for the cooling of power plants.
I’ll have to start taking shorter showers!
Link to thisWhoops, I should have been more specific. The “natural gas value” to which I was referring is “223 gallons/MWh”
Link to thisGreat article Melissa! Wouldn’t you agree that the energy source that suffers as a result of more wind is actually your second most water efficient power producer: natural gas? Since coal and nuclear are base load sources that cannot be cycled, the intermittent nature of all that new wind causes the decreases in the use of natural gas. For Texas to truly benefit, more natural gas capacity needs to be used for base load power, add on more wind to supplement, and continue to meet peaks with the only variable power source we have (natural gas)!
Great blog!
Link to this@iluvdubya – No, this value would not change if you changed the extraction method used. The 223 gallons/MWh value only includes water consumed at the power plant for cooling.
Link to this@CrimsonThunder – Thanks! Glad that you enjoyed the article.
You bring up a good point about the complex set of relationships that exist in our power systems. When we introduce intermittent power sources (like wind and solar), we have to figure out how to manage them. As Texas has added more wind power, its grid operator (ERCOT) has done a great job of this – balancing the desire to use the wind with the need to maintain reliability. You’re certainly right that natural gas could be given a lot of credit for enabling wind, since it provides a flexible back-up power resource.
I agree with you that using natural gas for power generation could lead to significant water savings compared to coal and natural gas. And Texas has a lot of natural gas capacity that it can use to realize these savings. For a state that is in the middle of a tough drought (like Texas), this is an interesting argument for pricing power differently to reflect the “true cost” of using so much water.
Great point. Thanks for sharing.
Link to thisVery informative content. The points you have highlighted really needs some deep thinking. The scarcity of water increasing day by day across the globe. There is really a big need to have some great plans and strategies in preserving and saving water effectively. I think at present there is no better alternative is there for producing electricity other then water. The main reason of choosing water is, it is a renewable resource and it is far more better than the coal and nuclear ones. The other renewable resources like sunlight and wind can’t be used for mass electric generation. So, water is only the available option. All we can do is, use electricity only when there is a need, don’t waste it. And also in our daily life we must try to minimize the water consumption, that’s the only solution which comes from my mind.
Link to this