Southern California Edison Re-Engineering Neighborhood Power Circuits To Accept Large Amounts of Fluctuating Solar Generation

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The design of traditional circuits that carry electricity through communities served by utilities like Southern California Edison (SCE) is changing significantly for the first time in more than 100 years.

These distribution circuits have been one-way routes for electricity channeled from neighborhood substations to some 1,200 nearby homes and businesses each. Components built into these power paths compensate for the natural drop-off in voltage, ensuring that the customer at the end of a circuit receives the same stable voltage supply as the one nearest the substation.

SCE has begun connecting large multimillion-watt solar power stations, with their fluctuating outputs depending on time of day and cloud conditions, to the middle of such circuits. To support this advance in distributed renewable generation, the utility's grid engineers have launched the first major redesign of this aspect of the traditional power delivery system.

"Power delivery engineers have long recognized that smarter distribution circuits would be needed – two-way power paths that include a new generation of components that can sense and adjust instantly to fluctuating power conditions," said Mike Montoya, SCE director of grid advancement.

"To support SCE’s decision to install large solar generation stations, our grid engineers have begun identifying, testing and helping the industry create these smarter distribution circuit technologies,” he said. “We are creating the future now."

One example of this work is the inverter testing program at SCE's Pomona, Calif., laboratory. Inverters used to convert the direct current output of solar panels to the alternating current customers use are connected to a grid simulator and subjected to real-world conditions. SCE engineers are collecting and analyzing data to determine how best to enable the safe and effective deployment of inverters on the utility’s distribution circuits.

Lessons learned as SCE deploys its network of 1-to-10-million-watt community solar plants, and upgrades its power distribution system, are being shared with other utilities and the solar industry to foster similar advances elsewhere.

SCE also announced today that four new solar power plants capable of providing 7 million watts of peak generating capacity (AC) – enough to serve 4,550 average homes – have been connected to the utility's Inland Empire grid, enlarging SCE's community solar network to 15 stations.

These new rooftop solar photovoltaic stations in Fontana and Redlands, Calif., join 10 others, which have been serving the utility's Inland Empire customers for up to three years, plus the utility’s first large ground-mount installation recently completed in the Central Valley.

Construction of the solar plants created 192 temporary Southern California jobs. SCE estimates its five-year solar project will result in 75 to 100 roof- and ground-mount facilities and up to 1,200 new construction jobs.

"When SCE announced its solar PV program in 2008, our primary goals were to help speed up California's deployment of solar generation while driving down the cost of photovoltaic panels for everyone," said Mark Nelson, SCE director of generation planning and strategy. "We are on target to meet those goals."

The Fontana installations involve three solar stations on more than 1.9 million square feet of leased warehouse roofs owned by Prologis and 35,000 photovoltaic panels.

In Redlands, SCE has built an additional solar station with 5,900 panels spread over 259,000 square feet of Prologis warehouse space.

History of SCE’s Solar Photovoltaic Program

The solar PV program SCE proposed to state regulators in March 2008 was approved in June 2009. At the direction of the state utilities commission, SCE expanded the program by offering long-term power purchase agreements to independent producers willing to build similar neighborhood plants. So far, the utility has awarded 29 such contracts, which will yield about 43 million watts (AC) of new solar photovoltaic power for SCE customers.

In response to its annual solicitation for renewable generation proposals, SCE also has seen an increase in the number of cost-effective solar photovoltaic bids. The winning bids show a significant reduction in the cost of providing such energy. In November 2010, SCE signed 20 purchase agreements, with the potential for 239 million watts (AC) of power.

About Southern California Edison

An Edison International (NYSE:EIX) company, Southern California Edison is one of the nation’s largest electric utilities, serving nearly 14 million people via 4.9 million customer accounts in a 50,000-square-mile service area within Central, Coastal and Southern California.

Edison International

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