SDG&E Completes Zero-Emissions Microgrid Pilot Project

SAN DIEGO, CA — San Diego Gas & Electric and Sumitomo Electric Friday announced they have completed a multiyear zero-emissions microgrid pilot project using a "vanadium redox flow battery" installed at the utility company's Bonita location.

Microgrids are mini power grids intended to operate independently of the larger grid and keep critical facilities powered during emergencies and Public Safety Power Shutoffs. The vanadium redox flow battery was touted as the first to be connected to the state's energy market when it went online in 2018.

According to SDG&E, in one of the test runs, the battery -- functioning as part of a microgrid -- powered 66 residential and commercial customers for close to five hours.

"Climate conditions increasingly threaten the continuity of essential services that our customers expect and deserve from us, which is one of the many reasons we are so focused on innovation and technology," said SDG&E CEO Caroline Winn. "There is a critical need to develop breakthrough solutions like zero-emissions microgrids to not only minimize disruptions, but to also support the transition to a cleaner, safer and more reliable energy grid of the future."

VRF batteries consist of tanks of liquid electrolytes and pumps that charge and discharge electrons to the grid, a company statement read. During the pilot, the batteries charged when solar energy was abundant and discharged during peak hours to meet demand.

"We are honored that the Sumitomo flow battery has contributed to the successful demonstration of this large-scale microgrid," said Hideo Hato, senior managing director of Sumitomo Electric. "Sumitomo's cutting-edge non- flammable and reusable flow battery system can help support California's climate goals and improve resiliency for the state's electric infrastructure."

According to SDG&E, the microgrid demonstration project was completed late last year and included two successful tests. One was a transition in which customers did not experience any loss of power when they were transitioned to the microgrid for electric service. The other was a black start -- meaning microgrid operators established and sustained service after a complete loss of power. Customers experienced a momentary outage before they were transitioned to the microgrid, which operated in island mode separate from the larger power grid. Tests were conducted during variable weather conditions.

In 2013, SDG&E began operating what it touts as the first utility- scale microgrid in America in Borrego Springs and is currently in the process of upgrading it to run on 100% renewable energy.

SDG&E is building four additional microgrids and is on track to integrate about 145 MW of utility- owned energy storage with the local grid in 2022.