Tapping the Wind and Sun to Save Water
by Bill Chameides | April 16th, 2008
posted by Erica Rowell (Editor)
Everyone knows we need green energy to fight global warming. But there’s another big reason to tap renewable power sources –- not enough water.
Large swaths of the Southwest and Southeast are in the throes of debilitating droughts. North Texas and Oklahoma’s recent dry spell dragged on from 2003 to the spring of 2007 (more on U.S. droughts). Droughts have even wiped out entire civilizations like the Anasazi (see Jared Diamond’s Collapse and Eugene Linden‘s Winds of Change).
But today’s water problems are far more profound than those of the Anasazi. The huge quantities we use — unprecedented in human history — make us more vulnerable to drought. Our water woes stem from an ever-increasing demand for water to slake the thirsts of a growing population on the one hand and to irrigate crops to feed that same population on the other.
Few people appreciate that yet another sector is clamoring for more water — the power industry. Fortunately we have the technology to wean this one from our dwindling supplies.
Another water hog: Conventional power plants
Have you noticed that power plants tend to be located near rivers, lakes or oceans? Do you know why? Easy, they need lots and lots of water.
Conventional and nuclear power plants, like the coal-fired plant pictured here on Lake Erie, are usually located by a lake or river because they need lots of water to operate. NREL/David Parsons
Coal-burning, natural gas-fired and nuclear power plants (which together produce about 90% of the country’s power) all generate electricity through a thermal process. They burn fossil fuels or split atoms to generate heat to boil water. The resulting pressurized steam turns a turbine that drives a generator that produces electricity.
It’s a process that produces lots of waste heat, which must be dissipated to keep the plant from overheating. So in addition to the source of water needed to make the steam (usually the nearby river or lake), even more water, generally much more than that required to make the steam, is needed to cool things down.
Because water is so integral to conventional and nuclear power production, strained water supplies put energy production at risk. A case in point is the Corette Power Plant in Billings, Montana, which siphons water daily from the Yellowstone River to produce electricity. The plant needs the river flow to be above 1,500 cubic feet per second to stay online. A recent dip below this level prompted a shutdown.
Unfortunately, this is not anomalous. Reduced water supplies are wreaking havoc across the country, fueling debate and water wars. A list of troubles includes:
- Florida’s Polk County trying to generate electricity without drying up wells,
- the decade-long fight between Alabama, Florida, and Georgia over who gets to draw how much water when (see this recent AP report and CNN video) and
- the receding waters of the once majestic Rio Grande, which failed to reach the Gulf of Mexico during much of 2001 and 2002.
Prognosis: Global warming means less water
Predicting the precise impacts of global warming is difficult, but by almost all indications things are not going to be pleasant. More specifically, there is a strong scientific consensus that water will be a big casualty of climate change. Higher temperatures will cause soils to dry out faster, making us more prone to long stretches of drought.
If this comes to pass, it could devastate our water system as increasing demands compete for a shrinking supply. Even without droughts, a warmer world will stress conventional power plant operations. The water used for cooling plants, which must be returned to its source after cooling, cannot be so hot that it undermines the river’s or lake’s ecosystem.
Severe heat waves can render cooling systems inoperable and cause shutdowns of power plants at the very time when demand for electricity is often the highest. During the 2007 heat wave, for instance, the Tennessee Valley Authority had to shut down a nuclear reactor because of high temperatures in the Tennessee River. Similar episodes have occurred in Europe.
We’re all too familiar with power outages and brownouts during hot spells, when the power grid is stressed to capacity. Global warming could make these events commonplace.
Among existing solutions, green power is the most potent
But it does not have to be that way. Weaning our power system off water would make it less prone to disruptions from shortages and rising temperatures while leaving more water available for municipal and agricultural needs.
Photovoltaic power plants, like this SunEdison plant in Colorado, draw very little water to generate electricity. As the world continues to wrangle over dwindling water supplies, green power could be a powerful solution. NREL/Steve Wilcox
A small number of tweaks to our current system is helping staunch the slowly evolving water crisis, but more needs to be done. Newer plants are being designed to use less water. Unfortunately, such efficiency doesn’t help the hundreds of old plants supplying much of our power. Alternative cooling methods are also being pursued, with several plants using dry or air cooling. But while such technology exists, a scant 600 plants worldwide use it.
Renewable energy offers a wide window of hope. Green power sources like wind and solar photovoltaics require tiny amounts of water. While such green solutions comprise only about three percent of our electricity, this could change and almost certainly must if we are to meet rising demands for drinking water and irrigation in a warming world.
Some say that green energy won’t be able to provide a significant portion of our electricity needs. But solving big problems usually requires thinking out of the box. Now I am just a dean, albeit at a great university, so what do I know about business, you might ask? I certainly wouldn’t suggest taking investment advice from me, but my guess is that the time is ripe for investing in green power. And high time it is.filed under: climate change, coal, drought, energy, faculty, natural gas, renewable energy, water
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