California Drought and Power Potential
California's grid gurus say they can make it through this summer, but the future may pose real problems for a hydro-heavy regional system.
As the grip of California's four-year drought tightens, will the long-running event crimp electricity generation in the state? So far, according to the California Independent System Operator (CAISO), which dispatches much of the power in the Golden State, the answer is "no," thanks to the state's burgeoning supply of renewable wind and solar power. But that situation could change if the drought conditions continue into future years.
In its 2015 Summer Assessment released in May, CAISO said, "Although California severe drought significantly reduces hydro power supply, the hydro generation reduction will not materially impact the reliability of the CAISO system this summer due to significant renewable generation additions, sufficient imports, and moderate peak demand growth."
The CAISO assessment notes the severity of the continued drought. "As of April 16, 2015," says the power agency's analysis, "the statewide hydrologic conditions were summarized as: 58 percent of average precipitation; 4 percent of April 1 average snowpack water content; and 60 percent of average reservoir storage according to California Department of Water Resources."
California's hydro capacity is 7,428 MW, but CAISO says that after discussions with Pacific Gas & Electric and Southern California Edison, the largest hydro utilities in the ISO, the regional operator is projecting a 2015 hydro derating of 1,511 MW in the base case and as much as 2,733 MW in the worst case.
Down All Over
Drought also has implications for steam-electric generation. The ISO says it is "tracking the thermal power plants' potential to be out-of-service due to water supply curtailments. Among the thermal units greater than 20 MW, four natural gas-fired plants that were identified to have water supply concerns during 2014 have addressed the issues by establishing alternatives or by monitoring and managing groundwater supply."
California's electric system has long depended on importing federal power from the hydro-rich Pacific Northwest in the summer over the California-Oregon Intertie. So far, the electricity from the Bonneville Power Administration system is keeping California supplied. But, according to the SNL online newsletter, the Army Corps of Engineers reports that hydro production from its dam system in Washington and Oregon is running 33% down for the year, after a strong early Spring runoff.
Taylor Dixon of the Northwest River Forecast said at a briefing this month, "With a few exceptions, precipitation this [water year beginning Oct. 1, 2014] has been relatively normal . . . . However, the big story . . . is warm temperatures across pretty much the entire Pacific Northwest that have resulted in low snow pack and early runoff in most locations." The entire state of Washington, along with 15 counties in Oregon and five in Idaho, are under a drought declaration.
At the end of May, according to the California Department of Water Resources, the state's snowpack essentially disappeared. While water remains in reservoirs, and the chief victim of California's drought is agriculture-which uses about 80% of the state's water-the vanishing snowpack is a symbol of the impact of the four-year drought. It means that most of the surface water supplies for farms and cities in the state are dangerously low (Figure 1).
1. Running dry. Like most of California's reservoirs, the Folsom Lake is well below normal levels. Courtesy: California Department of Water Resources.
Solar to the Rescue?
Renewables have played an important role in California's ability to deal with the drought while keeping electricity flowing, along with power from the Bonneville system and moderate load growth. CAISO said that between June 2014 to June 2015, 2,328 MW of new renewable generation reached commercial operation. Of that, 96% is solar, 3.4% wind, and 0.6% biogas.
What does the future hold for regional power supplies if the drought continues? (See Sidebar.) The state has seen longer droughts than this one. The New York Times in April noted that while the current drought is the longest since records have been kept, scientists have said that in the more ancient past, "California and the Southwest occasionally had even worse droughts-so-called megadroughts-that lasted decades. At least in parts of California, in two cases in the last 1,200 years, these dry spells lingered for up to two centuries. The new normal, scientists say, may in fact be an old one."
| Diablo Canyon, Water Savior? California has a giant thermal generating plant that not only is not affected by the state's drought, but can actually contribute to the state's supply of fresh water. Pacific Gas & Electric's (PG&E's) two-unit, 2,200-MW Diablo Canyon nuclear station takes water from the Pacific Ocean, strips out the salty components, and uses the pure water in the plant's operations (Figure 2). It can produce much more fresh water than it uses.
2. Water wise. Diablo Canyon, California's last surviving nuclear reactor, has unexploited seawater desalination capacity. San Luis Obispo County is looking into drawing on the plant's freshwater output. Source: Nuclear Regulatory Commission The plant uses reverse osmosis to produce makeup water for the two pressurized-water reactors. According to the utility, the plant can desalinate "more than 450 gallons per minute and is currently operating at 40 percent capacity to meet plant needs." The plant has a state permit to desalinate almost 1.5 million gallons daily. PG&E has an agreement with San Luis Obispo County to supply fresh water to fight wild fires in the county. The utility and the county Board of Supervisors are also working together on "a feasibility study on what steps would be involved to connect Diablo's desalination facility to existing waster infrastructure." An article in Forbes magazine adds, "San Luis Obispo residents use a lot of water, about 100 gallons per day, so this additional supply will only be enough water for about 8,000 households. But everything helps." At the same time, the environmental group Friends of the Earth (FOE) is waging a campaign to shut down Diablo Canyon, charging that the U.S. Nuclear Regulatory Commission has known about previously undisclosed seismic faults under the plant beyond what it was designed for, but refused to regulate. In a 3-1 vote, the NRC approved a FOE petition to refer the matter to the commission's independent Atomic Safety Licensing Board for review. (See "Seismic Hazard Resiliency at U.S. Nuclear Plants" in the April 2015 issue of POWER for more details.) FOE was also a leading voice in the campaign to force the retirement of Southern California Edison's San Onofre nuclear station in June 2013. Another challenge to Diablo Canyon's role as a freshwater provider is a pending rule by California's environmental regulators that would force PG&E to end once-through cooling and install closed-cycle cooling towers. The state is responding to federal Environmental Protection Agency (EPA) rules aimed at eliminating once-through cooling at existing power plants. The EPA already forbids once-through cooling for new plants. The utility is seeking a variance to the state mandate, arguing that the retrofit requirement will cost $4.5 billion. |
In an article in Nature in May, two Arizona State University engineering professors looked at the implications of a longer drought for the western U.S. They concluded, "For vulnerable power stations (46% of existing capacity), climate change may reduce average summertime generating capacity by 1.1-3.0%, with reductions of up to 7.2-8.8% under a ten-year drought. At present, power providers do not account for climate impacts in their development plans, meaning that they could be overestimating their ability to meet future electricity needs."
The authors called on power generators to increase transmission capacity and strengthen energy conservation strategies in order to adapt to long-term drought conditions. They also recommended greater development of non-hydro renewables.
-Kennedy Maize (@kennedymaize) writes about energy and is a long-time contributor to POWER.
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