Progress in deploying long duration energy storage by Xcel, Alliant and more buoys DOE interest in new technology

In a testament to what can be achieved through collaboration, the U.S. Department of Energy (DOE), the Edison Electric Institute’s Institute for the Energy Transition, the Electric Power Research Institute (EPRI) and the Long Duration Energy Storage (LDES) Council convened a group of specialists in the long duration energy storage field in Washington, on the day of the solar eclipse. The inaugural LDES Summit on Monday offered a view at how various non-lithium-ion storage technologies could be deployed at commercial scale.

Long duration storage is a key technology to many utilities for fully transitioning away from fossil fuels, as in the case of Xcel Energy, which aims to retire thousands of megawatts of coal in the Midwest by mid-2026 and looks to LDES as an option “to really bridge the gap” left by removing so much baseload power, Bria Shea, Xcel’s vice president of Regulatory for the Upper-Midwest Region, said at the summit.

Long duration energy storage technology is “foundational” to a resilient grid, Gene Rodrigues, DOE’s Assistant Secretary for Electricity, said. The DOE has an earthshot goal to lower the cost of storage that lasts for 10 hours or longer, announcing in September $325 million in funding for 15 projects across 17 states to pilot LDES technologies.

“You are not just the start of a partnership, you are the foundation of a movement that is absolutely necessary in this country,” Rodrigues said, prompting the participants of the summit to look around the room.

Multi-day storage, for instance, is already being piloted by Xcel Energy, and a panel bringing developer and regulatory perspectives together, outlined how they prioritized building strategic partnerships in Minnesota. Xcel is deploying two 10 MW, 1,000 MWh systems with Form Energy at retiring coal plants in Minnesota and Colorado, using iron-air batteries.

“We really also saw a lot of community benefits here, in addition to the state benefits for Minnesota in .. carbon emissions reductions,” Shea said. Particularly in Minnesota, which “has a rich iron availability. Other community benefits include the workforce development initiatives by the utility and job creation in the community from building the project. Xcel brought its proposal for the 100-hour energy storage system last year to the Minnesota Public Utilities Commission last year and received approval.

The opportunity to build out iron mining for further applications of this technology was very interesting to regulators, according to Minnesota Public Utilities Commission Chair Katie Sieben.

“I think it was because of the strength of the federal government and their work” to lower costs, Sieben said, crediting the Inflation Reduction Act. “Really, the IRA, combined with the breakthrough funding that this project also secured and, certainly and most importantly, Xcel’s leadership in going out and chasing a pilot, [convinced the PUC] this is something that we think will help our system.”

In its latest integrated resource plan filed in February, Xcel tripled the energy storage being brought online by 2030, from 200 MW to 600 MW, with thousands of megawatts following afterwards.

“Our modeling is getting more granular … identifying more hours of the year that need an offset, from dispatchable 24/7” resources, Shea said. Also, in part due to federal funding, “we are now seeing the pricing of storage to be more competitive” with gas, Shea said. 

The Form Energy pilot, still in the engineering and prepping phase, is expected to be in service next year.

In a panel on their pilot with Italian company Energy Dome, Alliant Energy outlined the local opportunities that its carbon dioxide-based storage system unlocked. Alliant, according to John Rainbolt, director of federal affairs, is committed to sourcing materials locally for the construction of a 10 hour energy storage system. This is made possible by Energy Dome’s design, which uses off-the-shelf components, to take excess energy off of the grid to convert CO2 into a liquid state, and to later power a turbine and send electricity back to the grid by heating up that liquefied CO2 back to its gas state.

“The closed-loop process, for us, is a really innovative way to try to demonstrate this technology on essentially the site of our soon-to-be retired coal plant, as a grid-tied asset,” said Rainbolt. 

“It was really the uniqueness of their technology, it was the efficiency of their technology that really drew us to the project,” he added. According to Energy Dome, its system will have up to 75 percent efficiency.

The program also brought together the other owners of the Columbia Energy Center, the coal plant that will be retired by the end of this year, and got the University of Wisconsin and EPRI engaged.

Of the 15 LDES projects funded by DOE, Alliant Energy received a $30 million grant for a carbon dioxide-based storage system. “We kind of think of them as like a 50 percent off coupon,” Rainbolt said, adding that the tax benefits received through the Inflation Reduction Act and other legislation focused on prioritizing the clean energy transition made the project work out financially.

As one of the largest wind energy operators in the country, Alliant also sees this project as critical to increasing energy storage in its portfolio, according to Rainbolt.

“We are very much interested in all the different technologies that are out there,” he said, noting Alliant’s 2 lithium ion projects that “sailed through the commission” last year, expected online to support two solar farms by 2025.

“Everybody outside of the four walls of this room talks about the energy transition as if it’s just something that’s going to happen and it’s going to be beneficial for everything and everyone,” Rodrigues, who named himself “the Eeyore of Energy,” told the crowd at the LDES Summit.

Re-emphasizing the need to ensure the clean energy transition is planned in a beneficial way for all, Rodrigues announced on behalf of DOE, three new projects focused on long duration energy storage, which will receive up to $5 million each to convene with technology, stakeholder and research institutions. Each new consortium represents a different approach for energy storage lasting more than 10 hours: New Lab is focused on zinc batteries, the Battery Council International will be focused on the use of lead batteries, and Clean Tech Strategies is working to accelerate flow batteries.