Anticipated reserves of electric capacity above and beyond supply are expected to be below targeted levels in Texas for the second summer in a row, according to North American Electric Reliability Corporation data.
Meanwhile, despite an overall improvement in its reserve picture, California’s reserves may be a concern under extreme weather and adverse supply conditions this summer, according to NAERC’s 2013 Summer Short-Term Reliability Assessment.
The electricity utility industry uses a simple strategy for maintaining reliability: always have more generating and transmission capacity available than may be required, taking into account unexpectedly high demand or the possibility of unplanned outages of generators or a major transmission line, according to the US Energy Information Administration.
Yet it can be difficult to forecast electricity demand in the future, and building new generating plants can take years, according to the EIA. The industry regularly monitors the supply situation using a measure called reserve margin. Grid planners compare these regional estimates of reserve margins to predetermined reference levels to assess supply adequacy.
Reserve margin calculations involve expectations about demand and supply at the time of the systems’ peak demand. Many factors can influence these calculations such as changes in economic activity, weather patterns, and various demand response programs that can affect expected peak demand. Supply changes come into play, too, such as generating capacity additions and retirements, transmission upgrades, and other factors likely to affect the availability of supply.
The peak demand projection for the three western regions increased by 2.7 percent on average between 2012 and 2013, and anticipated supply grew by 4.5 percent. In Texas, peak demand increased by 2.3 percent, while resources increased by 1.4 percent. The peak demand projection for the remaining regions in the East averaged 0.7 percent, with resources growing by 0.6 percent.
As recently as November, NERC estimated that the US had 63 GW of capacity above and beyond its summer 2013 target reserve supply.
In other energy supply news, Southern California’s electric power system is facing a number of challenges heading into the summer peak demand season, largely because of the prolonged outage of the two units at the San Onofre Nuclear Generating Station, which have been offline since January 2012, according to the EIA.
A combination of recent capacity additions and electric system upgrades made since June 2012 will help meet peak electric demand this summer, the agency says
The California Independent System Operator, the grid operator for most of the state, noted in its Summer Loads and Resources Assessment that 2,502 MW of capacity (capacity adjusted for planning purposes) have been added since June 2012, with an additional 891 MW slated to come online by June 1, 2013. The two off-line San Onofre units, in comparison, total 2,246 MW.
This new capacity will help make up for the loss of the generation from San Onofre, but the reliability issue is more complicated than simply providing replacement generation. Geographically, the San Onofre site is in a localized pocket of electric power demand near San Diego and Los Angeles. Given the characteristics of the electric transmission system, the loss of San Onofre limits the amount of power that can be brought into the area over the transmission grid—rather than generated locally—under some conditions. Much of the new capacity lies outside of the San Diego-Los Angeles area, meaning that additional transmission upgrades are needed to supply that area, the EIA says.