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SRP inaugurates 340MW/1,360MWh BESS assets ahead of Arizona summer peak challenges


An event on Monday (24 June) celebrated the opening of two large-scale battery storage systems in the service area of Arizona utility Salt River Project (SRP), including the southwest US state’s largest project of its type to date.

Salt River Project and developer Plus Power celebrated the commissioning and imminent start of commercial operations at the 250MW/1,000MWh Sierra Estrella Energy Storage facility and 90MW/360MWh Superstition Energy Storage facility.

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Sierra Estrella, in the city of Avondale, Maricopa County, is the largest standalone battery energy storage system (BESS) in Arizona so far.

Although Salt River Project (SRP) earlier this year added a slightly larger 260MW system at its Sonoran Solar Energy Center, that project charges directly from a solar PV array of the same nameplate generation capacity as its battery storage component’s output, making Sierra Estrella the largest to charge from the grid.

Superstition, in the town of Gilbert, also in Maricopa, is expected to come online this week, slightly earlier than its larger counterpart. Sierra Estrella has also finished its commissioning stage and is due to enter service ahead of the brutal Arizonan summer and the attendant spikes in peak energy demand that will entail.

Both projects availed of tax credit incentives through the Inflation Reduction Act (IRA), while SRP said the majority of EPC work was carried out by unionised workers.

SRP chief executive officer Jim Pratt said the BESS resources would “provide flexibility and resource diversity to help maintain reliable power during Arizona’s hot summers”.

In addition to targeting net zero carbon emissions by 2050, the utility is also projecting a requirement to double the amount of generating resources it can call on over the next 10 years as it retires some 1,300MW of coal-fired generation and accommodates rising energy demand in the Phoenix metropolitan area.

As set out in its 2023 integrated resource plan (IRP), SRP is deploying 1,100MW of new energy storage resources by the end of 2024 along with that increase in generation capacity.

‘Important to get project online before Arizona summer in full swing’

Both new standalone BESS projects are equipped with Tesla Megapack lithium-ion (Li-ion) BESS solutions designed and manufactured in the US. Plus Power developed both projects in consultation with first responders in Avondale and Gilbert to best understand and mitigate safety concerns.

Burns & McDonnell, the EPC for the Sierra Estrella project, said its completion was ahead of schedule. The project team took a number of “innovative steps” to get construction completed in less than a year, Burns & McDonnell claimed.

These included an “assembly line approach” to various construction stages, such as the equipment installation team being ready to work on the site as soon as concrete foundations were poured, and then installation of the 275 containerised lithium iron phosphate (LFP) Megapacks and commissioning all happening in sequence.

The EPC also factored in Plus Power’s plans for augmentation of the batteries over time, a topic Burns & McDonnell’s energy storage technology manager spoke to Premium about in a March 2023 interview. Burns & McDonnell’s Jason Barmann, who has since left his role to work with another ECP, noted in that article that with most BESS projects planned by developers for augmentation to begin within three to five years of the start of operation, the US industry will soon enter its first big wave of augmentations.

Utilities SRP, Arizona Public Service contracting toll agreements for large-scale BESS

“It was very important to have this project online before summer in Arizona was in full swing,” Plus Power CEO Brandon O’Keefe said.

“This project will play an important part in helping SRP meet its needs for sustainable and reliable energy.”

Plus Power’s 1,360MWh of storage was selected by the utility in an all-source request for proposals (RFP) launched in Q3 2021, with contracts signed by the pair about a year later giving SRP the rights to control the dispatch of the stored power to mitigate peak demand.

Plus Power got US$82 million in tax equity investment towards the Superstition project a couple of months ago from Morgan Stanley, building on a US$1.8 billion October 2023 fundraise toward five projects including the Arizona pair and three assets in Texas.

Canadian Solar’s project development arm Recurrent Energy recently secured US$513 million financing for another project in Maricopa County with a different Arizona utility, Arizona Public Service (APS).

Recurrent Energy and APS signed a 20-year tolling agreement for the Papago Energy Storage project following a 2022 RFP. It will be co-located with a 300MWac solar PV plant, and feature a 300MW/1,200MWh BESS, making it the state’s biggest BESS of any kind, albeit Sierra Estrella will be the biggest standalone facility in the state even after Papago comes online in Q2 2025.

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