May 04, 2012 Elizabeth McCarthy
Original source: http://www.cacurrent.com/storyDisplay.php?sid=6088
Rising temperatures and the continuing outage of the 2,200 MW San Onofre Nuclear Generating Station highlights the constraints and intricacies of Southern California’s grid. It also spotlights the other coastal power plants in the region.The region’s transmission system has more challenges than Northern California’s largely because of the area’s much larger and more urban population.
The region’s transmission system has more challenges than Northern California’s because of the area’s much larger and more urban population.
“The transmission system has not kept up with growth,” said Jesus Arredondo, energy consultant.
Several intertwined factors affect power flows along Southern California’s high voltage system. They include:
-High voltage line capacities;
-Thermal limits of power lines;
-Voltage support needs;
-Power plant locations;
-Line and plant outages; and
There are the added challenges of the state’s 33 percent renewable energy standard, greenhouse gas reduction law, and required phase-out of once-through cooled power plants. Further squeezes stem from emission credit constraints in the South Coast Air Quality Management District, which have largely halted power project construction, plus independent power project financing challenges.
Whether power gets to where it is needed, particularly on hot days, depends on the demand--how much, where, and at what time. It also hinges on whether power lines or plants are off line--which currently includes the massive San Onofre facility--and how much demand response can be counted on to manage supply shortages. In addition, there are the power line capacity limits, and “thermal limits,” the latter which arise from differing capacities of interconnected lines.
Key components of the Southland’s grid are the power plants that were built along the coast decades ago because that is where most of the people lived. Access to seawater for cooling spinning turbines was also a plus for plant developers These facilities hook up to lines that feed the Los Angeles basin. They later were extended to accommodate the growth in the hotter inland areas.
The Southern California coastal plants are considered by many critical to system reliability because of system constraints elsewhere.
Steven Kelly, Independent Energy Producers policy director, called the coastal plants “the anchor tenants” of the Southern California grid. They not only serve local power needs but also voltage support to help balance the system.
Of the approximately 17,000 MW of coastal plants about two-thirds are in the southern half of the state.
Two AES units at Huntington Beach are set to help fill the void left by the extended outage at San Onofre, which supplies the Los Angeles Basin and San Diego. Putting the 450 MW into the voltage lines as demand rises with the temperature has the added benefit of expanding by an additional 350 MW the capacity to import power from out of the area into San Diego, noted Steven Greenlee, California Independent System Operator spokesperson.
The largely independently-owned coastal power plants--many to be retrofitted to water-light cooling technologies to comply with the state’s mandate to phase out seawater cooling--likely will continue supplying needed local supplies.
In addition to these facilities’ ability to meet local reliability needs, chances are slim of getting new power plants constructed elsewhere given potent community opposition.
The lack of power purchase agreements with utilities, however, is a major hurdle to independent producers financing planned retrofits at coastal facilities.
The constrained Southern California transmission system is to get a boost from completion of San Diego Gas & Electric’s Sunrise Powerlink line, expected to go on line next month. Under the current configuration, the San Diego power infrastructure--referred to as a “cul de sac” because it is the end of the transmission system--can be affected by problems on two 500 kV lines. If one or both lines go down, a massive bottleneck or worse is created (see story at 5). That is because at the other end are five 230 kV lines from Orange County into San Diego, which are maxed out.
The new Sunrise line, according to CAISO, can import power from Arizona and Mexico--fossil-fueled and nuclear. However, its stated purpose was to accommodate expected solar and other new renewable projects, virtually none of which have gone online.
Additional transmission relief is expected from the Southern California Edison’s upgrade of the Barre-Ellis 230 kV line, which should increase power supplies for San Diego.
Still, however, meeting summer-time peak demand if San Onofre remains fully or partially closed falls largely to demand-response programs. The various energy curbing programs are expected to make up for more than 2,000 MW. That, plus 450 MW from the Huntington units, goes a good ways to filling a San Onofre power void. (It was reported in some major media May 4 that the nuclear facility may partially ramp up next month. However, there was no mention of that during Edison International’s May 2 financial quarterly report. Nor was it confirmed on Edison’s website or by federal regulators just prior to press time).
Southern California Edison demand-response programs are estimated to produce more than 1,060 negawatts. Where the energy savings are occurring has not been revealed. SDG&E’s price responsive programs are said to curb 84 MW, with another 20 MW cut from programs triggered when CAISO warns of supply constraints and calls a stage one emergency. On top of that, publicizing the need for conservation from the public via TV and radio can save up to 1,000 MW, said Greenlee.
But he acknowledged, “We are still cutting it very close.”Share This Post