The Energy Storage Report 2024

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NextEra’s 300MWh co-located BESS in Iowa approved by regulator


Iowa’s energy regulator has approved two projects from NextEra Energy Resources including a 300MWh co-located battery energy storage system (BESS).

The Iowa Utilities Board (IUB) said it will grant certificates of public convenience, use and necessity for the two projects from energy supplier NextEra once they have been approved by the Linn County Board of Supervisors.

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The projects are Duane Arnold Solar, a 50MW solar PV facility, and Duane Arnold Solar II, a 150MW solar PV plant with a 75MW/300MWh BESS (the size limits of the projects as per the IUB’s order).

The projects are close to the Duane Arnold nuclear station near Palo in Linn County, a facility majority-owned by NextEra which shut down in August 2020. This allows them to use the existing grid infrastructure and connections at the location, which falls within the remit of grid operator Midwestern Independent System Operator (MISO).

As previously reported by, NextEra already has a deal in place to sell the projects to utility Alliant Energy once operational, which is expected in 2024.

According to the IUB’s order document, the four-hour BESS at Duane Arnold Solar II will consist of 96 containers with space for an additional 48 battery containers for use in the future, as the capacity of the battery cells diminishes over time. It added that the BESS will serve to complement the solar facility by smoothing, shifting and firming the solar generation.

In a piece of concurrent news, Alliant Energy has turned a separate 5MW BESS project online in Cedar Rapids, also in Iowa, next to its Deer Run substation. It more than doubles Alliant’s BESS power in the state from 3.5MW to 8.5MW. The utility also operates in Wisconsin.

“While Alliant Energy has operated battery storage systems for several years, battery technology has advanced by leaps and bounds enabling new projects to deliver greater efficiency, performance and affordability,” said Mayuri Farlinger, vice president of customer and community engagement at Alliant Energy.

A press release said the 5MW BESS unit would store energy from the grid at times of the day when demand is low and release it when it’s needed to power homes and businesses. The company also plans to closely study the BESS system’s performance, design features and grid integration.

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