The Energy Storage Report 2024

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Arizona electric co-op AEPCO launches solar-plus-storage project with ‘up to’ 940MWh capacity


Arizona Electric Power Cooperative (AEPCO) has received board approval to deploy a solar-plus-storage project with up to 940MWh of capacity, after two smaller co-operatives completed smaller co-located projects in the state.

AEPCO can now enter into an agreement with Roadrunner Solar LLC and Roadrunner Storage LLC, affiliates of international developer and independent power producer (IPP) Enlight to develop a new solar project of up to 294 MWdc with a battery energy storage system (BESS) of up to 940 MWh, at the Apache Station in Cochise County.

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The Apache Solar II project BESS will be a 4-hour system, and the project is undergoing siting, design and permitting over the next several months with commercial operation expected in summer 2025.

Although the press release didn’t specify, utilities in Arizona have typically signed long-term ‘tolling agreements’ or power purchase agreements (PPAs) with BESS project operators for the offtake of a system. Enlight secured such an agreement for a separate solar-plus-storage project with a 824MWh BESS in August.

Patrick Ledger, AEPCO CEO said: “As a not-for-profit cooperative, we work with our member-owners and their boards and managers to ensure that investments in new resources are prudently made. Our objective is to provide affordable and reliable power, not to make a profit.”

“The Apache Solar II project demonstrates the advantage of smaller utilities coming together on a larger project, to take advantage of economies of scale and substantially reduced costs for all participants and their electric consumers at the end of the line.”

Arizona is fast-becoming one of the most active energy storage markets in the US, with long-term PPAs for energy storage helping to drive numerous large-scale projects. See all recent coverage of activity in the state here.

Electric co-operatives cover over half of the US’ land mass and often operate in regions with higher levels of poverty.

EDP and Silicon Ranch complete smaller projects in Arizona

In related news, two projects have come online over the last month also pairing solar and storage on a smaller scale in Arizona.

EDP Renewables North America (EDPR NA) has completed a solar-plus-storage project with a 60MWh BESS for Mohave Electric Cooperative (MEC), while Silicon Ranch has deployed a similar size system for another co-operative in the state.

EDPR NA held a ribbon-cutting ceremony for the new 23.27MWdc ground-mount solar array yesterday (25 October), which also includes a 15MW/60MWh BESS provided by system integrator Stem Inc.

The project was built for MEC, a not-for-profit member-owned electric cooperative utility.

Stem Inc will use its AI-driven energy management system (EMS) platform Athena to optimise the project BESS activity and its PowerTrack solar management for the solar array.

Tyler Carlson, CEO of MEC said: “We are pleased to be working with EDP Renewables on Mohave Electric Cooperative’s first solar plus storage project. This project demonstrates MEC’s proactive planning to increase reliability, meet renewable energy mandates, and support the overall electrical grid.”

EDPR NA is part of the Madrid-headquartered international developer and independent power producer (IPP).

The ceremony was also attended by the Alliance for Tribal Clean Energy, a non-profit that supports the efforts of Native American tribes to transition to clean energy, with a representative recognising the Mohave spiritual content of the land.

IIPP Silicon Ranch meanwhile announced the completion of the 20MW, 80MWh BESS McNeal Solar Farm, pictured above, earlier this month. The project was built for Sulphur Springs Valley Electric Cooperative (SSVEC), a not-for-profit member-owned electric cooperative utility.

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