In late May, San Diego Gas & Electric's Microgrid powered the entire community of Borrego Springs during planned grid maintenance, thus avoiding major service interruptions to customers. In addition to onsite generation and energy storage systems, SDG&E used NRG Energy's nearby 26-megawatt (MW) Borrego Solar facility to supply electricity to all 2,800 customers in the area. This solution is believed to be the first time in the nation that a microgrid has leveraged renewable energy to power an entire community.
"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," said Dave Geier, SDG&E's vice president of electric transmission and system engineering. "Borrego Springs was entirely separated from the main grid, running on the Microgrid's local onsite resources for nine hours as we conducted necessary maintenance. This ability to operate independently of the grid when necessary is exactly what the Microgrid was designed for and the fact that we were able to accomplish this using local renewable energy is an added benefit. We are very proud to offer this innovative service to the community."
SDG&E employed the Borrego Springs Microgrid because the transmission line that usually feeds the community had been damaged by lightning. SDG&E crews needed to replace or repair three transmission poles, which would usually require a 10-hour sustained outage to the entire community of Borrego Springs. However, SDG&E was able to call on the Borrego Springs Microgrid to avoid the impact of a major outage. The Borrego Springs Microgrid uses advanced technologies – including local power generation, energy storage, and automated switching – to create a more resilient local grid for the benefit of customers. The Microgrid is connected to the centralized energy grid, but can disconnect from the larger grid and function independently during emergencies, supplying vital electricity to the local community through its onsite resources.
SDG&E seamlessly switched over to the Microgrid to power the entire community at 8:45 a.m. on May 21, allowing the maintenance work to begin. The Microgrid generated the majority of power during this time from the large Borrego Solar facility, using batteries and traditional distributed generation to "follow the load" and fill in gaps created by the solar facility. This is necessary because solar power is intermittent by nature and requires back-up resources when solar becomes unavailable, such as when a cloud moves in front of the sun. The Microgrid uses advanced computer software and automated switching to ensure these fluctuations are accounted for in real time. This innovative network of resources working together to support each other kept a steady supply of power flowing to Borrego Springs throughout the day. At 5:30 p.m., SDG&E completed the grid maintenance and switched the town back to the main grid. Rather than having an extended, 9-hour outage, customers experienced a planned outage of less than 10 minutes as they were switched back from the Microgrid to the repaired transmission feed.
"The Microgrid was really a crucial tool during this maintenance," said Linda Haddock, executive director of the Borrego Springs Chamber of Commerce. "This innovative project provided electricity to our residents and kept the town running all day. Residents were also pleased that the Borrego Solar facility was used to support this effort. It's great to see all these local, sustainable resources being put back into the community to truly make a difference in the lives of our residents in Borrego Springs."
Using clean renewable energy to energize Borrego Springs was one of the main goals of a $5 million grant the California Energy Commission (CEC) recently awarded to SDG&E. The grant is allowing the Microgrid to connect to the Borrego Solar facility to power the entire community, making this one of the nation's largest microgrids that can operate solely on renewable energy. In addition to bringing in more clean power, the funding is being used to increase the size of the Microgrid to service all of Borrego Springs, further enhancing local reliability and reducing the duration of power outages. SDG&E accomplished both these goals of using the solar facility and powering the entire community with the Microgrid for the first time during the recent grid maintenance.
SDG&E's success during the outage is the first step in implementing the CEC's grant. SDG&E plans to incorporate more advanced computer software and sensors to continue to enhance the Microgrid. These innovations will broaden the Microgrid's use of renewable energy to power the entire community and allow this type of outage response to become routine and standardized. The physical improvements are expected to be completed by mid-2016. In 2008, the U.S. Department of Energy (DOE) provided SDG&E with $8 million in grants that helped launch the Borrego Springs Microgrid. By avoiding a lengthy outage, the Microgrid demonstrated its ongoing potential to put the CEC and DOE funding to good use, creating a true renewable energy Microgrid that will enhance reliability, promote innovation and benefit all customers.