Microgrid technology makes history in California

Microgrid technology makes history in California

Borrego Springs is California's only Dark Sky Community, a light pollution-free haven for astronomers and stargazers surrounded by the Anza-Borrego Desert State Park. Because of its extremely rural location, sometimes "dark sky" takes on another meaning; the area is prone to extensive power outages from severe storms, forest fires and even earthquakes. After a series of damaging wildfires resulted in prolonged service interruptions in 2007, San Diego Gas & Electric (SDG&E) began to fix the problem by turning to microgrid technology for the region.

Today, the Borrego Springs microgrid is the largest utility-scale microgrid operating anywhere in the nation. The unit was put to the test in May, when SDG&E relied exclusively on the microgrid to power the entire community for nine hours during a planned outage to repair damage from a windstorm to a utility pole. In addition to energy storage systems and on-site generation, the microgrid uses a nearby solar facility to generate power. It represents the first time in the U.S. that a solar-based microgrid was used to power an entire community.

Power to the people

During the planned outage, all 2,800 residential customers in Borrego Springs were temporarily converted to receive their energy from the 26-megawatt Borrego solar facility. "This [facility] is the first of a kind that fully integrates renewable resources at a distributed level as well as a specialized level to maintain continuity of service to a large block of diverse customers," said Jim Avery, SDG&E's chief development officer, in a recent interview. "We utilized the sun to serve an entire region of our system while isolating that area from the rest of the grid."

The microgrid is connected to the centralized energy grid, but can disconnect and function independently during emergencies. The only time that Borrego Springs customers lost service was for a brief period when power was switched back to the main grid. SDG&E, which received a $5 million grant from the California Energy Commission in March to expand its microgrid technology, is working on installing relay and protection control devices that will prevent any disruption in service in the future, even during reconnection.

Although the microgrid powered the community for eight hours, it could have lasted longer if necessary. The total amount of time and energy available depends on the time of the year, especially during the summer months when demand is the greatest. If a wildfire were to damage transmission lines leading into the area for a prolonged period, SDG&E would likely maintain service for an area for one or two circuits, then rotate those circuits so all residents would have periodic power. This would prevent a prolonged outage. In the winter months, when energy load is lower, the microgrid could power Borrego Springs for up to 48 hours.

Major potential for microgrids

Microgrids represent a concept that is quickly gaining momentum in the utility sector. Based on the success of the Borrego Springs pilot, SDG&E is working on a number of other microgrid projects, especially for areas serviced by long transmission lines susceptible to fire, windstorm and other natural disasters. Many utilities are also looking at microgrids as a way to work around widespread outages. They allow utilities to maintain power at critical facilities such as hospitals, military bases and high-security government buildings.

In general, microgrids provide a unique opportunity for utilities to rethink the way they build out their infrastructure. Historically, providers such as SDG&E would not have considered locating major generation assets in discrete areas like Borrego Springs; there was no way to serve that area in the event of an outage. Microgrids, however, solve that problem.

"I think it will just be a matter of time before you see this kind of technology everywhere," says Avery.

Source: IBM Big Data & Analytics Hub

Smart Grid Bulletin February 2019

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