Dive Brief:

• In what San Diego Gas & Electric believes is a first in the nation, the utility used a solar-based microgrid to provide power to an entire community during planned maintenance, thus avoiding a significant outage.
• Predominately fueled by a 26 MW solar facility owned by NRG Energy and supported battery storage and small diesel generators, the microgrid supplied power to 2,800 customers in Borrego Springs for nine hours.
• The town's connection to the microgrid was one of the primary goals of a $5 million grant the California Energy Commission awarded SDG&E.

Dive Insight:

SDG&E has pulled off what it believes is the nation's first example of a renewables-fueled microgrid being used to provide power for an entire town in a real-world scenario. 

Just before 9 a.m. on May 21, the utility "seamlessly" switched the Borrego Springs community over to microgrid power, and then switched it back nine hours later when maintenance was complete. The utility said in a statement that it used batteries and traditional distributed generation to “follow the load” and fill in power fluctuations from the solar facility.

“SDG&E demonstrated in a real-world situation how we can use innovative technology to create a more resilient and sustainable grid for our customers,” Dave Geier, SDG&E’s vice president of electric transmission and system engineering, said in a statement.

The utility used the Borrego Springs Microgrid after the transmission line that usually feeds the community was damaged by lightning. SDG&E said its crews needed to replace or repair three transmission poles, which would usually require a 10-hour sustained outage.

SDG&E said that using solar generation to power Borrego Springs was one of the main goals of a $5 million CEC grant, making it one of the nation’s largest microgrids that can operate solely on renewable energy.

As of the completion of the demonstration project, the Borrego Springs microgrid consisted of two 1.8 MW diesel generators, a 1500 kWh (500 kW) battery at the substation, three smaller 50 kWh batteries, six 8 kWh home batteries, and 700 kW of solar, according to the Lawrence Berkeley National Lab. The 26 MW solar facility used to help power the Borrego Springs community is owned by NRG Energy.

The utility said it plans to incorporate more advanced computer software and sensors to continue to enhance the microgrid, and said the innovations will broaden the microgrid’s use of renewable energy. Ultimately, SDG&E said the microgrid response to maintenance will "become routine and standardized." Physical improvements to the microgrid are expected to be completed in the middle of next year, and by mid-2016.