Power Flow

Cutting greenhouse gas emissions at U.S. power plants could help save some water too, a new analysis concludes.

Coal-fired and nuclear power plants are among the nation’s thirstiest water users, Munish Chandel and two colleagues at Duke University in Durham, North Carolina, report in Energy Policy. In 2005, electricity generators sucked up roughly 143 billion gallons per day – or 41% of all withdrawals from freshwater rivers and lakes, according to the U.S. Geological Survey. And in 2010, they estimate that 89% of U.S. electricity was produced at plants that required vast quantities of cooling water, with coal-fired plants using the most. But the trio wondered: How might new policies aimed at curbing climate change alter water use at U.S. power plants?

To find out, they first rounded up statistics on how water is used at power plants using different technologies and cooling techniques. Then, they used an analytical model to forecast how the nation’s power-generating mix might look like in 2030 under four policy scenarios, all of which were based on proposals that have been floated in Congress. All call for imposing some kind of a price on carbon dioxide emissions as a strategy to reduce emissions and foster the development of cleaner energy supplies, but differ in the pace and scope of proposed changes.

It turned that what was good for the atmosphere was good for the aquasphere too. “Under all the climate-policy scenarios, freshwater withdrawals decline 2–14% relative to a business-as-usual (BAU) scenario of no U.S. climate policy,” the authors conclude. “Furthermore, water use decreases as the price on [carbon dioxide] under the climate policies increases.” Much of the forecast decrease is a result of coal-fired plants installing new, more efficient cooling technologies, they note. But some is also the result of the construction of new nuclear power plants – which may be unlikely.

The study also suggests that if carbon prices get high enough – more than $50 per ton — they could actually cause water use at power plants to soar. That’s because high prices could make it worthwhile to install water-intensive “carbon capture and storage” systems that trap carbon dioxide emissions and pump them underground. “While climate policy should have a generally positive impact on freshwater withdrawal in power generation, we also project that on a regional level, Florida, New York, Texas and New England will increase freshwater consumption 30% above BAU by 2030 if carbon prices become high enough to spur significant CCS retrofits… These projections, however, assume no limit to water availability, which in fact could restrict the locations and extent to which CCS might be implemented nationally.”

It could be challenging, it appears, to balance our growing thirst for both power and water. David Malakoff | August 15, 2011

Source: Chandel, M.K., et al., The potential impacts of climate-change policy on freshwater use in thermoelectric power generation. Energy Policy (2011), doi:10.1016/j.enpol.2011.07.022

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