Inside the nation’s first renewables-plus-storage microgrid

By Robert Walton, Utility Dive

Borrego Springs, California, sits less than 100 miles from San Diego, but in terms of electric reliability the two places were once worlds apart. San Diego Gas & Electric serves 3.4 million consumers with 1.4 million electric meters in its territory. And last year – for the ninth consecutive year – it was named the most reliable Western utility by PA Consulting Group.  But if you lived in Borrego Springs, an isolated desert community surrounded by a state park, your utility experience was markedly different.

“That area has seen outages over the years, some lasting days on end,” according to Jim Avery, SDG&E’s chief development officer. “Borrego Springs is served by one radial transmission line traversing 60 miles of exposure. It is susceptible to wildfires, windstorms, flooding and hail.” After wildfires knocked out power to the area in 2007 for two days, the utility took a hard look at how to better supply residents and businesses. About 2,800 people live in the community, which is entirely surrounded by Anza-Borrego State Park, the largest park in California.

“As a result of the wildfires, we decided we were going to rethink the way we served communities such as Borrego Springs,” Avery said. “We started our quest for designing a fully-integrated microgrid, one that could integrate conventional sources of generation, renewable sources, such as rooftop solar, as well as substation and utility-scale solar.” The system also includes distributed energy storage and batteries located at substations. With the help of $8 million from the U.S. Department of Energy, “we’ve gone through an evolution in the last seven years towards building that ultimate microgrid,” Avery said. “And we’ve had some opportunities to test it under different conditions.”

The grid was used to avoid some smaller outages, and then earlier this year the California Energy Commission awarded the utility a $5 million grant to expand, allowing it to interconnect with the nearby 26-MW Borrego Springs solar facility.

In late spring, major flooding did damage to SDG&E’s transmission corridor – potentially leaving customers in the dark again. Historically, that would have meant a 10-hour outage as the utility rebuilt the poles. “We would have had customers out of service for almost an entire day,” Avery said. “But because the microgrid was up and running we were able to switch over all of our customers to be fed by the rooftop solar systems scattered out in the community, in addition the large-scale solar, and it was all balanced by the batteries located on the distribution line and at our substations.” Borrego Springs’ peak load is about 14 MW, and rooftop plus utility-scale solar give the community about 30 MW of generation. The batteries can store about 1.5 MW.

Borrego Springs isn’t the only microgrid out there, of course. It’s not even the only one operated by SDG&E, which has a few other grids in place for voltage regulation. But, according to Avery, it is the first of its kind to power an entire community with renewable energy.

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