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Arizona just added its biggest grid battery yet, with another coming soon

The state is shoring up clean energy supply for a new Google data center during a record year nationally for energy storage installations.
By Julian Spector

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An aerial view of a large construction site with a craggy mountain range in the distance
Construction underway at the Sierra Estrella Energy Storage project in Avondale, Arizona (Plus Power)

Arizona just added its biggest grid battery so far, part of a nationwide trend toward unprecedented energy storage installations this year.

Grid batteries have soared from obscurity to become the second-most popular type of power plant expected to be built in the U.S. this year — more than gas, more than wind — in fact, more than gas and wind put together. This surge in popularity gives the grid more tools to absorb surplus renewable energy production and shift it to the times of day when it’s needed most, but it also helps the grid operate more efficiently on normal days and during extreme weather events.

The proliferation of new grid batteries is playing out on the ground in Arizona, where renewables juggernaut NextEra Energy Resources just activated its Sonoran Solar Energy Center. The project adds 260 megawatts of solar and 1 gigawatt-hour of storage to the greater Phoenix-area grid controlled by utility Salt River Project, which heralded the installation as the largest grid battery in the state of Arizona.

That title will soon have to be shared: Developer Plus Power is currently constructing its own 1-gigawatt-hour battery for SRP in Avondale, known as the Sierra Estrella project. That one is expected to join the grid this summer. Arizona, in short, is adding multiple record-busting big batteries in just a handful of months.

Google signed up as the anchor tenant for the Sonoran solar project, to supply clean energy for its forthcoming Mesa data center.

The tech giant aspires to match its electricity usage with clean generation on an hourly basis to reduce the amount of fossil-fuel combustion necessary for its round-the-clock operations. But full hourly matching of consumption to clean power production at a desirable price point remains out of reach for tech leaders and their clean energy suppliers for now. The Mesa project is slated to match 80% of its hourly consumption with clean energy flowing to the grid from the Sonoran project. Leftover output from the solar-plus-battery plant can serve other businesses and households in SRP’s territory.

Data centers and AI computing have triggered a historic increase in near-term electricity demand, catching utilities and grid planners by surprise across the country. Some utilities are looking to increase their investment in gas turbines to keep pace with demand, but that approach locks in new carbon emissions for years, if not decades. Google’s Arizona strategy models a different path: bringing dispatchable clean energy online in the places where it’s building the data centers.

Arizona enjoys a dry, sunny climate that makes solar highly competitive, even in the absence of meaningful state-level climate policies. Utility Arizona Public Service began contracting for solar-battery peaker plants as early as 2018, after recognizing that cheap solar paired with increasingly affordable batteries could beat the costs of new gas construction. But a planned buildout was halted when an early battery project exploded in April 2019, injuring four emergency responders.

Battery development resumed after a detailed investigation of the causes of the failure, and Arizona has reclaimed its place as a leading battery installer, after the heavyweights of California and Texas.

Salt River Project delved into large-scale batteries more recently — despite the objections of community groups and climate advocates, the utility has tended to prefer expanding its fleet of gas power plants. Arizona’s utility regulators blocked one such plan in the historically Black community of Randolph in an April 2022 vote, forcing the utility to look elsewhere for new electricity capacity.

Now, SRP’s fleet will boast two of the nation’s largest lithium-ion battery systems. The company will also build a 5-megawatt/50-megawatt-hour pilot project of a novel flow-battery technology from German startup CMBlu, in an effort to explore alternative tools for longer-duration storage than what lithium-ion currently provides.

Julian Spector is a senior reporter at Canary Media. He reports on batteries, long-duration energy storage, low-carbon hydrogen and clean energy breakthroughs around the world.