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Arizona utility SRP brings online 25MW / 100MWh Tesla Megapack battery storage project

Tesla Megapacks at the Bolster substation site, adjacent to SRP’s Agua Fria Generating Station power plant. Image: SRP.

A 25MW four-hour (100MWh) battery storage project has been connected to the grid by Arizona utility company Salt River Project (SRP).

SRP said last week that the project at its Bolster substation is currently the biggest standalone battery energy storage system (BESS) in the southwestern US state, sited adjacent to the utility’s 626MW Agua Fria Generating Station thermal power plant in the City of Peoria. 

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Using Tesla Megapack BESS equipment, the batteries can be charged at off-peak times when power is cheaper and more plentiful, like night time or during times of surplus solar generation, and then discharged during peak periods to help meet customer demand. SRP said that while it doesn’t directly charge from renewable energy, as the amount of renewables on the utility’s networks increases, the amount of renewables integrated to the grid by the BESS can increase too. 

“Battery storage is an extremely important and growing component of SRP’s 2035 Sustainability Goals to reduce our carbon footprint. The Bolster Substation Battery System adds to our already considerable investment in battery storage and further allows us to offset carbon-emitting resources by storing energy and providing it to our customers when they need it most,” SRP’s chief strategy, corporate services and sustainability executive Kelly Barr said. 

SRP serves about a million customers in the Phoenix metropolitan area and in May upped its commitment to renewables by setting a target of adding 2,025MW of new solar generation by 2025 but has more recently faced criticism for a proposal announced in September to invest US$1 billion in expanding one of its gas power plants.  

The utility also has two pilot BESS projects in operation from which it collects data, one is a 20MW integrated solar-plus-storage plant and the other is a 10MW / 40MWh standalone BESS. 

In addition to owning those projects and the Bolster substation project in Peoria, SRP has also signed long-term contracts for the outputs of two large-scale battery projects under construction: one is the Sonoran Energy Center, which will have a 250MW solar PV array and a 1GWh BESS and the other, Storey Energy Center, will be an 88MW solar-plus-storage project. Both are expected to enter service in June 2023 and were announced in 2019.

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