DISTRIBUTECH International attendees had the opportunity to tour California’s first utility-scale Vanadium Redox Flow (VRF) battery and microgrid.

In 2021, San Diego Gas & Electric (SDG&E) and Sumitomo Electric (SEI) demonstrated the use of the VRF battery in creating a zero-emissions microgrid, capping off a six-year effort. The first-of-its-kind battery was installed at an SDG&E substation in 2017.

A presentation on the project and panel discussion on the future of long-duration energy storage was held before the SDG&E tour. It included representatives from the California Energy Commission (CEC), the National Renewable Energy Laboratory (NREL), Sumitomo Electric, CAISO and SDG&E.

SDG&E said the six-year demonstration project showed the VRF battery can effectively be used in various ways, including the ability to adjust supply and demand as more renewable energy is adopted or improving the resilience of local power supply during extreme weather events. The 2MW/8MWh system powered 66 residential and commercial customers for close to five hours.

“We need storage that can sustain us not just for hours, but for days, and potentially weeks,” said Caroline Winn, CEO of SDG&E. “I think storage that can synchronize supply and demand over longer time horizons is really what’s needed.”

She added: “If we can figure out how to scale up flow batteries in a cost-effective manner, it has the potential to be a game-changer.”

Photo by Clarion Energy.

Different from more prevalent stacked lithium-ion battery cells, Vanadium Redox Flow batteries consist of tanks of liquid electrolytes and pumps that charge and discharge electrons to the grid.

Stakeholders have touted several benefits to the VRF battery technology, including a versatile design that addresses both short and long periods of output variation. Other benefits include a projected service life of 20+ years, with the ability to accept an unlimited number of charge-discharge cycles without degradation.

As SDG&E staff members told tour attendees: “You can’t kill this battery.”

The vast majority of storage systems in California use lithium-ion batteries, which generally can dispatch power for up to four hours.

Mike Gravely, who is Research Program Manager at the California Energy Commission, said the state is working hard to open up opportunities for non-lithium ion technology.

“I think as it relates to [Long-Duration Energy Storage], it’s going to be an all of the above approach,” he said. “We shouldn’t start picking winners and losers right now. We should see the market evolve and see where it goes.”

Panelists from the California Energy Commission (CEC), the National Renewable Energy Laboratory (NREL), Sumitomo Electric, CAISO and SDG&E speak on the future of long-duration energy storage on Feb. 6. Photo by Clarion Energy.

Panelists agreed integrating long-duration storage for renewable energy is critical to helping California reach net-zero by 2045. They noted three factors critical to its future: availability, degradation profile and multi-use nature.

“If you’re going to participate in the ISO, can you qualify for resource adequacy or capacity?” raised Fernando Valero, Director for Advanced Clean Technology at SDG&E. “Can you qualify for ancillary services?”

“From a utility perspective, those are the things that we really take into account,” he added.

“I think the word of the year is scalability,” said Martha Symko-Davies, Laboratory Program Manager for Energy Systems Integration at the National Renewable Energy Laboratory (NREL). “[How to take] what Sumitomo did, not take six years but shorten that lifespan- and do it many more times successfully.”

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