POET and Antora launch 5 GWh thermal energy storage beside South Dakota ethanol plant

South Dakota’s Big Stone City has become a focal point for a new energy storage project aimed at turning excess wind power into usable heat for industrial production. In a partnership announced by POET and Antora Energy, the companies said a thermal energy storage system adjacent to POET’s ethanol plant has launched as a large-scale project designed to store low-cost electricity for later use when demand and grid conditions shift.

The system, the companies said, has a capacity of 5 gigawatt-hours and uses thermal storage to absorb energy that might otherwise be lost because of limits on the existing power grid. Officials said the arrangement is intended to provide a more reliable power source for the ethanol facility, particularly during times when the grid needs energy and when variable renewables such as wind would otherwise be curtailed.

Antora’s chief executive, Andrew Ponec, said in interviews that the project represents the first time Antora’s thermal storage technology has been put into commercial production. He also pointed to the choice of Big Stone City as tied to existing infrastructure, including POET’s biofuels plant and another power plant on site, as well as the city’s location on the Midcontinent Independent System Operator, or MISO, power grid.

The companies described how the storage works as turning electricity from wind into heat, then using that heat to support ethanol manufacturing. They said the thermal system collects low-cost off-peak energy from virtually any source—citing local wind turbines in this case—and stores it in insulated blocks of solid carbon that can reach temperatures of 4,000 degrees Fahrenheit. When the stored heat is needed, it is transferred into an oil and carried to industrial users, including the POET plant next door.

At the ethanol facility, the stored heat is converted into steam that powers boilers, distillers and other machinery involved in producing ethanol and related byproducts, the companies said. POET’s president and chief operating officer, Jeff Lautt, described the problem the project addresses as a lack of a “switch for the wind,” saying wind generation doesn’t necessarily match steady power demand and that the storage system is built to meet that need.

Lautt said the project also improves the operation of POET’s plant by adding a reliable source of sustainable energy across different demand periods. The companies said they expect this reliability to improve efficiency and increase outputs at the ethanol plant, with the developers also tying the industrial benefits to potential downstream effects for corn growers and consumer costs at the gas pump.

In addition to the energy-storage portion of the project, the companies pointed to jobs and development. The report said construction and development of the plant supported 300 new construction jobs in South Dakota and California and that it is expected to generate new full-time employment in the Big Stone City area.

Ponec said the project uses very little water and does not create substantial emissions. He also said the thermal storage facility was built in less than a year, that it is already providing power to POET’s plant, and that it should be fully online in October.

The thermal system is also being positioned in contrast to shorter-duration battery storage. Ponec said lithium-ion systems store actual electricity and only for a few hours, while thermal storage holds energy as heat for longer periods and can stabilize the grid and reduce consumer costs. The report added that South Dakota may also see other energy-storage projects, including lithium battery efforts in Codington and Brookings counties.

Supporters cited bipartisan backing for thermal storage and related energy development. A May 19 project release from POET and Antora included statements of support from U.S. Sens. John Thune and Mike Rounds, U.S. Rep. Dusty Johnson and South Dakota Gov. Larry Rhoden, according to the report; Rhoden and Rounds emphasized the project’s economic and jobs impact in South Dakota and its potential to boost domestic energy production.

In interviews, Ponec said most of the costs for the Big Stone project were paid through private financing led by Grok Ventures of Australia, rather than U.S. government funding. He said Antora makes money by selling energy to POET, and Lautt described the arrangement as a way to capture excess wind power that otherwise would be wasted while reducing natural gas use at the ethanol facility.