The growing lack of cooling water resources could decrease power generating capacity in the U.S. by between 4% and 16% and between 6% and 19% in Europe between 2031 and 2060, and the likelihood of extreme drops in generation as a result will almost triple, suggests a new study by European and University of Washington (UW) scientists.

The study, published in the journal Nature Climate Change, was funded by the European Commission. It suggests warmer water and reduced river flows have in recent years led to reduced production, or temporary shutdown, of several thermoelectric plants. The scientists cite as an example the Tennessee Valley Authority’s Browns Ferry Nuclear Plant in Alabama, which, shut down more than once last summer because the Tennessee River’s water was too warm to use for cooling.

In the next 50 years, warmer water and lower flows—caused by increasing air temperatures associated with climate change—will lead to more such power disruptions, the study says.

Thermoelectric plants, which use nuclear or fossil fuels to heat water into steam that turns a turbine, supply more than 90% of U.S. electricity and account for 40% of the nation’s freshwater usage, it says. In Europe, thermoelectric plants supply three-quarters of the electricity and account for about half of the freshwater use.

"This study suggests that our reliance on thermal cooling is something that we’re going to have to revisit," said co-author Dennis Lettenmaier, a UW professor of civil and environmental engineering.

While plants with cooling towers will be affected, the study shows that older plants that rely on "once-through cooling" will be most vulnerable. These plants pump water directly from rivers or lakes to cool the turbines before returning the water to its source, and they require high flow volumes.

The most significant effects in the U.S. will be at power plants situated inland on major rivers in the Southeast that use once-through cooling, such as the Browns Ferry plant in Alabama and the New Madrid coal-fired plant in southeastern Missouri, it projects.

The study used hydrological and water temperature models developed by Lettenmaier and co-author John Yearsley, a UW affiliate professor of civil and environmental engineering. Authors from the Institute of Energy and Climate Research in Germany and Wageningen University and Research Centre in the Netherland combined these with an electricity production model and considered two climate-change scenarios: one with modest technological change and one that assumed a rapid transition to renewable energy. The range of projected impacts to power systems covers both scenarios.

"Higher electricity prices and disruption to supply are significant concerns for the energy sector and consumers, but another growing concern is the environmental impact of increasing water temperatures on river ecosystems, affecting, for example, life cycles of aquatic organisms," said first author Michelle van Vliet, a doctoral student at the Wageningen University and Research Centre.

Given the high costs and the long lifetime of power plants, the authors say, such long-range projections are important to let the electricity sector adapt to changes in the availability of cooling water and plan infrastructure investments accordingly.

One adaptation strategy would be to reduce reliance on freshwater sources and place the plants near saltwater, according to corresponding author Pavel Kabat, director of the International Institute for Applied Systems Analysis in Austria and van Vliet’s doctoral adviser.

"However, given the life expectancy of power plants and the inability to relocate them to an alternative water source, this is not an immediate solution, but should be factored into infrastructure planning," he said. "Another option is to switch to new gas-fired power plants that are both more efficient than nuclear- or fossil-fuel-power plants and that also use less water."

Source: University of Washington