Fluence and Invenergy partner on 1,900MWh Arizona solar-plus-storage project

July 28, 2025
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Lithium-ion battery storage system integrator Fluence and independent power producer (IPP) Invenergy will be partnering on the 475MW solar and 1,900MWh energy storage Hashknife Solar Energy Centre in Navajo County, Arizona, US.

According to Fluence, Hashknife will be one of the largest solar-plus-storage facilities in Arizona, and will use the company’s Gridstack and Gridstack Pro lithium-ion energy storage solutions.

The project will be built in two phases. Hashknife I entered construction in 2024 and is expected to begin commercial operations in 2026. Hashknife II is expected to begin construction this year and will begin commercial operations in 2027.

Invenergy’s 2024 construction update for Hashknife I indicates that both phases have signed power purchase agreements (PPAs) with utility Arizona Public Service (APS) and are included in APS’s biggest portfolio of projects obtained through a request for proposals (RFP).

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The company also says the project will support 450 construction jobs during peak construction and create 16 full-time jobs. Invenergy expects the total economic investment to be US$53 million.

Fluence launched the Gridstack series in 2020, claiming it to be a highly customisable yet mass production modular battery energy storage system (BESS) solution. Gridstack Pro followed in 2023, which Fluence said at the time was aimed at the largest and most complicated projects its customers are undertaking.

At the beginning of the year, the company launched SmartStack, an integrated AC block with balance-of-plant (BOP) components housed underneath the battery stacks. By essentially making the units taller while increasing energy density, the company aimed for a smaller footprint on the ground.

Invenergy recently lost federal funding for its Grain Belt Express project, which aims to connect four US grid regions with a single transmission line. The company states that this would enhance energy affordability and reliability. Moreover, consumers linked to this grid and neighbouring grids would benefit, even if their utility does not buy power from Grain Belt Express.  

The company also claims it would have the ability to power 50 data centres, create an estimated US$52 billion in energy cost savings over 15 years, and create approximately 22,300 jobs during the construction of the line and new generation.

The US Department of Energy’s (DOE) Loan Programs Office (LPO) announced on 23 July that it had cancelled a US$4.9 billion loan guarantee for the Grain Belt Express Phase 1 project.

Several sources have claimed that lawyers at the LPO advised that the action was illegal. Invenergy has said it expects to find private funding for Grain Belt.

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