By Jonathan Marshall
With temperatures setting new records across the country, and over half of the continental United States now experiencing serious drought, global warming is no longer just a prediction of climate scientists. It’s a reality, here and now.
Though every sector of human activity is feeling the impact, electric utilities are feeling them especially keenly, as they struggle to keep up with peak summer demand for air conditioning. At the same time, heat and drought threaten to curb their ability to generate and transmit power in the first place.
As Matthew Wald reported in his Green blog, one power plant in the Midwest was recently curtailed and another shut down altogether because river water levels dropped too low for their cooling intake valves. This was no fluke. A number of Texas power plants reduced their output in 2011 due to water shortages. Three years earlier, many more plants throughout the drought-stricken Southeast came close to shutting down.
Even when cooling water is available, the efficiency of thermal generating plants declines when water temperatures rise too high for adequate cooling. That can mean lower power output than normal, at the very times when demand for electricity peaks.
Heat and drought impact nuclear production
Bloomberg News reported recently that heat and drought have dragged the production of U.S. nuclear power plants to a nine-year low. “Heat is the main issue, because if the river is getting warmer the water going into the plant is warmer and makes it harder to cool,” David McIntyre, a spokesman for the Nuclear Regulatory Commission, told Bloomberg.
A study published this June in Nature Climate Change predicts that higher average river temperatures, and declining river flows caused by global warming, may cut the peak summer capacity of fossil- and nuclear-power plants by 4.4 to 16 percent by mid-century. Plants along the lower Mississippi River and on the East Coast will suffer the most.
California utilities won’t be exempt, however. At a conference held last winter on the impacts of climate change on California, Maximilian Auffhammer, a professor in the department of Agricultural and Resource Economics at University of California, Berkeley, predicted that persistently hotter temperatures will drive up electricity consumption 50 percent by the end of the century—before even factoring in population growth.
At the same time, warming will cause “a pretty big” decline in the amount of snow in the Sierra Nevada, leading to “a profound impact on water supply for California,” observed Marty Ralph, chief of the water cycle branch at the National Oceanic and Atmospheric Administration.
That in turn may throttle back a lot of the clean, flexible hydroelectric power production that customers of PG&E and other utilities have long enjoyed.
“With the help of a dedicated scientist on staff, PG&E has been very closely evaluating the potential effects of climate change on hydro power generation for many years,” said David Moller, a director of power generation at the utility and president of the National Hydropower Association. “We do expect some change and we believe we are already seeing some. In our service area, the prediction is the amount of precipitation will stay roughly the same, but its form will change. If more comes in the form of rain than snow, it will run off quickly unless there is more storage. As a result, a lot of water will be unavailable for generation.”
PG&E choices benefit customers
Matters look better for PG&E on other fronts. The Diablo Canyon Power Plant, the largest source of generation in the utility’s service area, is cooled by ocean water, not by rivers that could dry up.
The utility also has three state-of-the-art gas-fired generators that use advanced air cooling rather than “wet” cooling.
For PG&E’s Gateway plant in Eastern Contra Costa County, located next to the Delta, “We made the environmentally conscious decision not to use river water or a wet cooling tower,” said Steve Royall, director of fossil and solar generation at PG&E. “Instead we went to an air-cooled condenser design, which uses 97 percent less water. The change to dry cooling was one reason the plant was named Project of the Year by Power Engineering magazine in 2009.”
Royall also noted that the air-cooled condensers at both the Gateway and Colusa generating stations are sized to support full output at ambient temperatures above 100 degrees, minimizing the risk of shrinking capacity that may occur at other facilities around the country from continued warming.
“PG&E’s long engagement on climate-change issues reflects more than our general concern for the environment,” said John Conway, PG&E’s senior vice president for energy supply. “We’ve served our customers well for more than a hundred years by adapting to the huge changes that have taken place in California over that period. To continue serving them well for the next hundred years and beyond, we are committed to understanding, predicting, and adapting to the equally huge changes that may affect our state’s environment.”
Email Jonathan Marshall at firstname.lastname@example.org.