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Eos and Invinity supplying battery systems to CEC-funded ‘biggest renewables microgrid in US’


Invinity Energy Systems and Eos Energy Enterprises are providing long duration energy storage systems to the ‘biggest renewables microgrid project in the US’, being developed for the Viejas Tribe of Kumeyaay Indians in Southern California.

That claim is from Invinity CEO Larry Zulch, Viejas Tribe Chairman John Christman and Allen Cadreau, CEO of the developer behind the project, Indian Energy, in an exclusive interview with

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Eos’ zinc batteries the second of three non-lithium technologies

Eos Energy Enterprises has been revealed as the supplier of a zinc-hybrid cathode battery storage system totalling 3MW/35MWh for the 60MWh microgrid project which received a US$31 million grant from the California Energy Commission (CEC) last week. Eos’ order is worth US$13.5 million.

The microgrid project will also include 15MW solar PV and will provide power to the Viejas Casino and Resort, located on the lands of and owned by the Tribe, described as the economic ‘lifeblood’ of the Tribe by Christman.

It will provide renewable backup power to the community through critical services at the site during outages, and allow the tribe to shift electricity use away from the statewide grid and reduce costs by load shifting the solar production. It is expected to come online in H1 2023 and will be optimised using Indian Energy’s in-house software platform.

Vanadium redox flow battery (VRFB) company Invinity Energy Systems is providing a 3MW/10MWh unit, its largest to-date and the largest flow battery in North America, as reported last week. The remaining 15MWh of the energy storage has not been contracted yet, Indian Energy CEO Allen Cadreau told, but is it not planned to be lithium-ion.

A ‘perfect storm’ leads to largest renewable microgrid in US

Speaking about the origins and development of the project, Christman said: “This was essentially a perfect storm, where the speed of how we were able to partner with Indian Energy was mind-boggling. I’ve never seen so many government agencies move so quickly.”

“Indian Energy proposed a microgrid project a while back, which we were really in need of at the time due to numerous SDG&E (a utility) power shutoffs. We wanted to be able to power the community without portable power generators. People in the community have also constantly been asking when we are going to go into solar to go green. That partnership went into a flywheel project at first before morphing into this solar microgrid.”

He added that the microgrid project would help the local community adopt the additional energy infrastructure needed to decarbonise, citing EV chargepoints as an example.

“We have a need to contract with known good long duration energy storage, and enrolling the banks to be able to bank these technologies is a struggle right now. Indian Energy’s vision along with the Viejas is to come together and prove these technologies through the RICU at MCAS Miramar,” added Cadreau, referring to Indian Energy’s advanced energy storage testing facility to validate long duration technologies at the Marine Corps Air Station (MCAS) Miramar.

“As the Tribe is located at the end of a power line the quality can also be an issue, which can have huge impact on the local economy. The microgrid platform is designed to be able to dynamically load follow.”

Asked why Indian Energy opted for non-lithium technologies, Cadreau added: “Lithium-ion is wonderful but it’s just not utility scale capable. We knew from the beginning that it was not going to be capable of doing the heavy lifting we want it to.”

Zulch agreed that the project would provide a testing ground for scaling up Invinity’s technology up to grid-scale, but also that it could demonstrate the feasibility and practicality of large-scale microgrids more widely.

“It creates an alternative vision for future energy delivery in California, one which at its core has microgrids in areas like the Native tribes’ where there’s an ability to think differently,” he said.

The CEC’s grant is the first of some US$380 million that California will put towards long duration energy storage technologies in the state, starting with US$140 million in fiscal year 2022-23. Christina Snider, Tribal Affairs Secretary to Governor Gavin Newsom who announced the funding, said the Viejas grant was most likely the largest awarded to a tribe in the US, ever.

Christman and Cadreau both agreed the project would have gone ahead without the CEC’s funding but at a smaller scale. Cadreau conceded that, although as a whole the project had been ‘seamless’, the gap between the different bridge loans needed up until now was ‘a bit of a struggle’.

“Building the biggest renewable energy microgrid is always going to have its difficulties but we don’t accomplish things by being conservative, we accomplish them by setting big targets,” Zulch said.

Christman added: “This is exciting. We want to get this up and running by next year, when we’ll hopefully be able to report that we are a successful operation that is off of the grid, though there’s a lot of working parts with this obviously.”

Invinity Energy Systems also provided one of its battery units for the largest existing hybrid battery energy storage system in the world, the Energy Superhub Oxford in the UK, which you can read more about here.’ publisher Solar Media will host the 5th Energy Storage Summit USA, 28-29 March 2023 in Austin, Texas. Featuring a packed programme of panels, presentations and fireside chats from industry leaders focusing on accelerating the market for energy storage across the country. For more information, go to the website.

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