POET, Antora Energy Bring 5 GWh Thermal Storage Online at South Dakota Bioethanol Facility

The Problem: Industrial Heat Needs Don't Align with Wind Output

POET's Big Stone City bioethanol facility needed continuous thermal energy to increase production, but wind generation in the region comes in surges and lulls that don't match manufacturing demand. Storing electricity in batteries and converting it back introduces efficiency losses that make economics difficult at industrial scale.

The Solution: Solid Carbon Thermal Batteries with Direct Heat Delivery

Antora Energy installed a 5 GWh thermal energy storage system that sidesteps thermoelectric conversion entirely. The system charges during wind surplus periods, storing energy as heat in insulated blocks of solid carbon. When POET needs heat, the thermal energy flows directly to industrial processes without a steam cycle in between.

Antora worked with Otter Tail Power to develop an electric rate approved by the South Dakota Public Utilities Commission. The rate lets the system charge selectively during local wind surplus without shifting costs to other consumers.

Construction to first energy delivery took under 12 months. Full operational status is expected later this year.

"This is what reindustrialization looks like—American innovation driving industrial competitiveness, domestic supply chains spanning a dozen states, and jobs from the factory floor to the construction site," said Andrew Ponec, Antora CEO.

The Results

The completed system will rank among the world's largest energy storage installations by capacity. POET receives around-the-clock thermal energy under a long-term heat offtake agreement, enabling higher bioethanol output. The project leverages supply chains across multiple states.

Senator Mike Rounds (R-SD) noted the project's economic impact for the region while boosting domestic energy production.

Engineering Implications

This deployment tests whether thermal storage can serve continuous industrial loads at scale. The direct thermal delivery approach avoids roundtrip losses that limit electrochemical storage in high-temperature applications. If the Big Stone City system performs as projected, it establishes a viable template for integrating variable renewable generation with steady industrial heat demand.

The specialized rate structure also matters. By enabling selective charging during surplus periods, Otter Tail Power's approach lets the system capture value from wind variability without destabilizing the broader grid.

M4S TAKE

My take: capacity expansions signal confidence, but the real question is whether demand justifies the spend. I watch for follow-up announcements about utilization rates or new contracts. Without those, this is just capital allocation.

Simon McLoughlin