“Weather conditions are increasingly threatening the continuity of essential services that our customers expect and deserve from us, which is one of the many reasons why we are so focused on innovation and technology,” said Caroline Winn, CEO of SDG&E. “Developing breakthrough solutions such as zero-emission microgrids is essential not only to minimize disruption, but also to support the transition to a cleaner, safer and more reliable energy grid of the future. »
Different from more common stacked lithium-ion battery cells, VRF batteries consist of reservoirs of liquid electrolytes and pumps that charge and discharge electrons to the grid. According to the U.S. Department of Energy, VRF technology has several advantages, including the potential for storing MWh of energy in simple designs, the ability to discharge energy for up to 12 hours at a time, and the fact that VRF batteries do not present a fire hazard. and use no highly reactive or toxic substances, can sit idle for long periods of time without losing storage capacity, and more. Disadvantages include the fact that VRBs generally have lower energy densities than other battery types (although increased energy density would help reduce costs and expand applications), the current draw of Standby can result in power loss, the technology’s small operating temperature window requires the use of air conditioning systems which can result in significant power losses, and the cost of the vanadium electrolyte.
During the pilot, the batteries charged when solar power was abundant and discharged during peak hours to meet demand.
The microgrid demonstration project was completed late last year and included two successful tests. One was a seamless transition in which customers suffered no loss of power when transferred to the microgrid for electric service. The other was a black boot, where microgrid operators established and maintained service after a total power outage. Customers suffered a momentary outage before being transferred to the microgrid, which operated in island mode separated from the power grid. The microgrid provided energy service as expected, even on cloudy days when solar power generation was not optimal.
SDG&E began operating America’s first large-scale microgrid in 2013 in Borrego Springs and is currently in the process of upgrading it to run on 100% renewable energy. The utility is building four additional microgrids and is on track to integrate approximately 145 MW of utility-owned energy storage with the local grid in 2022.