Two interconnected battery energy storage system (BESS) projects totaling more than 500 MWh in capacity are now online in South Texas and connected to the Electric Reliability Council of Texas (ERCOT) grid.

Battery supplier Wärtsilä Energy and projects owner Eolian L.P., a portfolio company of Global Infrastructure Partners, say the combined projects make up the “world’s largest (in MWh) fully-merchant and market-facing energy storage facility built to-date.”

A Wärtsilä spokesperson told Power Engineering the exact MWh capacity per project site was confidential. She did say each of the two sites are greater than 250 MWh and longer than 2 hours in duration, so the project is above 500 MWh in total.

The Madero and Ignacio lithium-ion battery projects have a combined power capacity of 200 MW and will be operated using Eolian software.

Wärtsilä said this is also the first use of the Investment Tax Credit (ITC) for standalone utility-scale energy storage systems, which was introduced through the Inflation Reduction Act (IRA) of 2022. 

Construction of the projects began in January 2021.

“Texas needs more flexible capacity solutions like energy storage for grid support and energy resource optimization,” said Risto Paldanius, vice president Americas, Wärtsilä Energy. “This will help the state as it faces the natural replacement cycle of older inflexible generators and adapts to more frequent extreme weather events.”

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