Climate change is cutting the productivity of nuclear power plants and other energy generating facilities as summers get hotter. That's because heat raises the temperature and lowers the volume of cooling water.
Nuclear plants along the Connecticut River were affected this summer by heat and drought. In Vernon, Vt., near Brattleboro and not far from the Massachusetts border, the Vermont Yankee plant had to lower its energy output four times in July because of high water temperature and reduced flow in the river. In Waterford, Conn., the Millstone power plant was off line for two weeks in August because water from Long Island Sound was too warm to cool it. Nuclear Regulator Commission guidelines say the water must be no warmer than 75 degrees, but water from the Sound averaged 1.7 degrees higher than that.
Another problem that's exacerbated by heat and drought is the warming of waterways into which power plants discharge coolant. The state of Illinois this summer granted four coal-fired plants and four nuclear plants special permission to discharge water as hot as 97 degrees, though the normally permitted high temperature is 90 degrees. Discharging water warmer than regulations generally allow is ecologically damaging because water too warm for fish and plants is even more harmful when the volume of water in the receiving body is low.
Around 40 percent of fresh water in the U.S. is used for the production of energy; the production of energy for an average household expends five times as much water as the household uses directly (for drinking, cooking and bathing). Increasingly, energy competes for water with agriculture and with our need for water itself.
Drought has raised the temperature and lowered the volume of cooling water for nuclear and other power plants before, but the outlook is for those things to happen more often.
Dennis Lettenmaier, a researcher at the University of Washington, in June published a study that found that power plants in the U.S., including nuclear plants, will see their power generation fall by 4 to 16 percent between 2031 and 2060 as temperatures warm. In Europe, Lettenmaier calculated, the drop could be between 6 and 19 percent. Needless to say, most of the reductions in power output will occur in the summer, when higher temperatures boost the need for air conditioning.