One of the world’s largest energy storage projects has begun operating at a rural biofuels site in South Dakota, according to a report distributed by The Associated Press. The project pairs a thermal energy storage system with POET’s ethanol plant in Big Stone City, a community officials and developers say serves as an energy hub for much of the Great Plains.
Antora Energy of California has partnered with South Dakota-based POET to launch the thermal storage facility adjacent to the ethanol plant, the report said. Officials said the system is designed to capture excess, low-cost energy from wind turbines that might otherwise be lost because of limits on the existing power grid, then store that energy for later when demand requires it.
The thermal storage facility is described as having a capacity of 5 gigawatt-hours. Antora’s executives and POET’s leaders said the storage will support more reliable power availability for the ethanol operation, including during shifting peak and off-peak demand periods, while also providing a pathway for wider use of the technology, the report said.
Project leaders said the technology works by collecting low-cost off-peak energy and storing it as heat in insulated blocks of solid carbon. They said the blocks reach 4,000 degrees Fahrenheit, after which the stored heat can be transferred into an oil that carries it to industrial users, in this case the POET plant next door. At the ethanol facility, the heat is then routed into steam that powers boilers, distillers and other machinery used in ethanol production and related byproducts.
In remarks included in the report, POET COO and President Jeff Lautt said the system addresses a problem created by how wind generation varies. “They’re taking excess wind energy that doesn’t have a home on the grid and otherwise would be wasted, and they’re capturing that,” Lautt said. He added that there is “nobody’s got a switch for the wind,” describing the mismatch between steady electricity demand and variable wind output.
Antora CEO Andrew Ponec said the location and configuration of the project were driven by existing energy users and grid conditions in the area, including POET’s biofuels plant and another power company plant on the site. He said Big Stone City was selected partly because it sits as a major hub on the regional Midcontinent Independent System Operator, or MISO, power grid. “We’re an energy technology company, so we’re going to go to wherever there are big concentrations of energy users,” Ponec said.
The report also described how the storage process is intended to translate electricity input into industrial heat output. Ponec compared it to a giant toaster, saying electricity from the wind turbines heats carbon blocks that then generate heat to run the plant. He said the system uses very little water and does not create substantial emissions, according to his comments, and that the facility was built in less than a year.
Beyond the Big Stone City site, the report laid out anticipated benefits tied to renewable integration and regional economic activity. Lautt said the storage would improve efficiency and increase output at the ethanol plant, aiming to reduce natural gas use and associated costs. The report said the companies also pointed to opportunities for corn growers through expanded markets for grain converted to ethanol, and to job creation tied to construction and operation.
A May 19 press release shared statements of support from U.S. Sens. John Thune and Mike Rounds, U.S. Rep. Dusty Johnson, and South Dakota Gov. Larry Rhoden, the report said. Rounds said in the release that “America’s need for energy is continuing to rise year after year,” adding that “the more of that energy we can take right here at home, the better,” and he said the Big Stone City project would have “a real economic impact in South Dakota while also creating jobs and boosting our domestic energy production.”
The report said Antora and POET described the system as the first to be put into commercial production by Antora, and that it is already supplying power to the ethanol plant with full operation expected in October. It also noted that Ponec said most costs were covered through private financing led by Grok Ventures of Australia, while he said thermal storage has received bipartisan support, including in legislation enacted in 2025. The companies said Antora makes money by selling its energy to POET, and they framed the arrangement as a way to lower power costs for the ethanol plant while enabling greater storage of renewable energy.