Ah, yes–the energy/water nexus.
Carbon, Carbon Everywhere But What About the Water?:
The connection between most energy and water starts with one simple fact: Except for wind and photovoltaic solar found on rooftops, most power plants big or small do one basic thing: They boil water.
That’s it.
The water then makes steam, which spins a turbine, which runs a generator, which creates electricity in a way that is almost miraculous. But with that miracle comes a price: Water. Lots and lots of it.
No matter if it is coal-powered, or nuclear, or oil or even large-scale solar thermal, all that heat has to be cooled down.
Thus the water. And when it is used for cooling, some of it is lost. It takes at least one gallon of water to create one kilowatt hour of power – enough to run your air conditioner for one hour. That water is consumed, not just used.
The numbers tell the tale: Rachelle Hill and Dr. Tamim Younos of Virginia Tech University estimate that “fossil fuel thermoelectric plants use between… 8 to 16 gallons of water to burn one 60-watt light bulb for 12 hours per day. Over the duration of one year this one incandescent light bulb would consume about 3,000 to 6,300 gallons of water.”
That’s a lot of water for a little bit of energy.
Other household appliances are just as thirsty: A central air conditioner running for 12 hours a day will drink up 16,800 gallons of water every year at the power plant. A laptop computer uses 200 gallons a year. A coffee maker perking two hours a day needs 672 gallons of water every year to brew that cup of Joe.
Different types of power plants require different amounts of water. The Department of Energy says coal and oil plants need about a gallon or two per kilowatt-hour (kWh). Hydro plants in the Northwest, for example, need 18 gallons for the same amount of energy. Power plants in Arizona use 7 gallons per kWh. In South Dakota, the Department of Energy says the average is 72 gallons of water per kWh. In California, its 4.5 gallons of water per kWh.
These numbers are all about water that is consumed – not just withdrawn. In California, 49 percent of all the water withdrawn in the state is used for energy.
…
The water it takes to create energy is still only half the picture. It also takes a tremendous amount of energy to move, treat and ultimately dispose of water.
In California, 20 percent of the energy in the state is used to move water. We use water to create energy, and we use energy to create water – to create more energy to create more water. And on and on and on it goes in a downward spiral – like the “two spent swimmers that cling together” – that completely distorts the way we think and act about water and power. Whenever we waste energy, we waste water.
Bingo. This is why I’ve been saying for some time that once we start taking water withdrawal and consumption into account it will alter our technology preferences for generating electricity. Consider this the water equivalent of “putting a price on carbon”; it’s a largely unpriced side effect that circumstances will force us to price, either explicitly or less formally and implicitly.
Please take a moment to ponder those California numbers: 49% of water withdrawal is for energy, and 20% of electricity is used simply to move water. That’s a lot of drops and electrons, by any measure.
For a broader and deeper view of US water use, the best reference I’m aware of comes from the USGS (US Geological Survey), USGS Water Use in the United States. That page has links to the most recent report (2005), as well as prior reports and related material. You can also download a spreadsheet of the country-level data for the US from the 2005 report page.
The abstract of the 2005 report:
Estimates of water use in the United States indicate that about 410 billion gallons per day (Bgal/d) were withdrawn in 2005 for all categories summarized in this report. This total is slightly less than the estimate for 2000, and about 5 percent less than total withdrawals in the peak year of 1980. Freshwater withdrawals in 2005 were 349 Bgal/d, or 85 percent of the total freshwater and saline-water withdrawals. Fresh groundwater withdrawals of 79.6 Bgal/day in 2005 were about 5 percent less than in 2000, and fresh surface-water withdrawals of 270 Bgal/day were about the same as in 2000. Withdrawals for thermoelectric-power generation and irrigation, the two largest uses of water, have stabilized or decreased since 1980. Withdrawals for public-supply and domestic uses have increased steadily since estimates began.
Thermoelectric-power generation water withdrawals were an estimated 201 Bgal/d in 2005, about 3 percent more than in 2000. In 2005, thermoelectric freshwater withdrawals accounted for 41 percent of all freshwater withdrawals. Nearly all of the water withdrawn for thermoelectric power was surface water used for once-through cooling at power plants. Twenty-nine percent of thermoelectric-power withdrawals were saline water from oceans and brackish coastal water bodies.
Withdrawals for irrigation in 2005 were 128 Bgal/d, about 8 percent less than in 2000 and approximately equal to estimates of irrigation water use in 1970. In 2005, irrigation withdrawals accounted for 37 percent of all freshwater withdrawals and 62 percent of all freshwater withdrawals excluding thermoelectric withdrawals. Irrigated acreage increased from 25 million acres in 1950 to 58 million acres in 1980, then remained fairly constant before increasing in 2000 and 2005 to more than 60 million acres. The number of acres irrigated using sprinkler and microirrigation systems has continued to increase and in 2005 accounted for 56 percent of the total irrigated acreage.
Water withdrawals for public supply were 44.2 Bgal/d in 2005, which is 2 percent more than in 2000, although the population increased by more than 5 percent during that time. Public supply accounted for 13 percent of all freshwater withdrawals in 2005 and 21 percent of all freshwater withdrawals excluding thermoelectric withdrawals. The percentage of the U.S. population obtaining drinking water from public suppliers has increased steadily from 62 percent in 1950 to 86 percent in 2005. Most of the population providing their own household water obtained their supplies from groundwater sources.
Self-supplied industrial water withdrawals continued to decline in 2005, as they have since their peak in 1970. Self-supplied industrial withdrawals were an estimated 18.2 Bgal/d in 2005, a 30-percent decrease from 1985. An estimated 4.02 Bgal/d were withdrawn for mining in 2005, which is 11 percent less than in 2000, and 18 percent less than in 1990. Withdrawals for mining were only 58 percent freshwater.
Livestock water use was estimated to be 2.14 Bgal/d in 2005, which is the smallest estimate since 1975, possibly due to the use of standardized coefficients for estimation of animal water needs. Water use for aquaculture was an estimated 8.78 Bgal/d in 2005, nearly four times the amount estimated in 1985. Part of this increase is due to the inclusion of more facilities in the estimates in 2005, and the use of standardized coefficients for estimating aquaculture use from other data.
Fresh surface water was the source for a majority of the public-supply, irrigation, aquaculture, thermoelectric, and industrial withdrawals. Nearly 30 percent of all fresh surface-water withdrawals in 2005 occurred in five States. In California, Idaho, and Colorado, most of the fresh surface-water withdrawals were for irrigation. In Texas and Illinois, most of the fresh surface-water withdrawals were for thermoelectric power generation.
About 67 percent of fresh groundwater withdrawals in 2005 were for irrigation, and 18 percent were for public supply. More than half of fresh groundwater withdrawals in the United States in 2005 occurred in six States. In California, Texas, Nebraska, Arkansas, and Idaho, most of the fresh groundwater withdrawals were for irrigation. In Florida, 52 percent of all fresh groundwater withdrawals were for public supply, and 34 percent were for irrigation.
I also recommend the US Dept. of Energy’s document, Estimating Freshwater Needs to Meet Future Thermoelectric Generation Requirements [108 page, 1.6MB PDF].
And don’t forget the monster’s third head, climate change. This is really the energy/water/climate nexus. How does climate come into this warped picture?
The most obvious way (at least to people who read this site and see me write about it all the time), there’s the lack of water to push turbines in hydro plants.
We also have more demand for air conditioning (read: electricity) in hotter summers, and one of the least discussed problems, reduced cooling capacity for thermoelectric plants. As rivers get warmer and their levels drop, it gets harder, or even impossible, to cool nearly all electricity plants powered by coal, oil, natural gas, and nuclear power, as well as some geothermal and solar thermal plants.
For a much more detailed look at this aspect of the e/w/c nexus, see Impact of Drought on U.S. Steam Electric Power Plant Cooling Water Intakes and Related Water Resource Management Issues [91 page 1.5MB PDF], which says in its introduction:
During the summer and fall of 2007, a serious drought affected the southeastern United States. As shown in Figure 1, a part of this area of the country is still experiencing extreme drought. In 2007, river flows in the southeast decreased, and water levels in lakes and reservoirs dropped. In some cases, water levels were so low that power production at some power plants had to be stopped or reduced. The problem for power plants becomes acute when river, lake, or reservoir water levels fall near or below the level of the water intakes used for drawing water for cooling. A related problem occurs when the temperature of the surface water increases to the point where the water can no longer be used for cooling. In this case, the concern is with discharge of heated water used for cooling back into waterways that are just too warm to keep temperatures at levels required to meet state water quality standards. Permits issued under the Clean Water Act (CWA) National Pollutant Discharge Elimination System (NPDES) program limit power plants from discharging overly heated water. For example, the Tennessee Valley Authority (TVA) Gallatin Fossil Plant is not permitted to discharge water used for cooling back into the Cumberland River that is higher than 90°F (WSMV Nashville 2007).
The southeast experienced particularly acute drought conditions in August 2007. As a result, nuclear and coal-fired plants within the TVA system were forced to shut down some reactors (e.g., the Browns Ferry facility in August 2007) and curtail operations at others. This problem has not been limited to the 2007 drought in the southeastern United States. A similar situation occurred in August 2006 along the Mississippi River (Exelon Quad Cities Illinois plant). Other plants in Illinois and some in Minnesota were also affected (Union of Concerned Scientists 2007). Given the current prolonged drought being experienced in the western United States (see also Figure 1), and also the scarcity of water resources in this region in general, many western utilities and power authorities are also beginning to examine the issue. The problem has also been experienced in Europe as well. During a serious drought in 2003, France was forced to reduce operations at many of its nuclear power plants (Union of Concerned Scientists 2007).
So, now you know. Help spread the word: Water matters, and it’s yet another way in which business-as-usual climate change will be very bad news for human beings.
