The world’s largest thermal energy storage plant by POET has been launched in Big Stone City, South Dakota. POET has partnered with Antora Energy to launch the 5-gigawatt-hour project deemed one of the largest of its kind. The system stores excess wind energy in carbon blocks heated to 4,000 degrees Fahrenheit. Once stored, it is later used to power POET’s adjacent ethanol plant.  The facility was built in under a year and supported 300 construction jobs. Furthermore, it is Antora’s first commercial production site. It aims to increase ethanol production efficiency, expand markets for South Dakota corn growers and reduce fossil fuel reliance.

During implementation, the project received bipartisan support and was funded primarily through private investment led by Grok Ventures. The plant is already providing power to POET’s facility, which produces 92 million gallons of ethanol annually. Moreover, the plant should be fully operational by Q4 of this year in October. Storage projects across the US are becoming fundamental such as Virginia’s largest battery storage project by Swift Current.  As of 2026, the 150 MW / 600 MWh Prospect Power project, Virginia’s largest battery storage asset by Swift Current Energy, was acquired in January by Elevate Renewables. Located in Rockingham County, the facility is on track to begin commercial operations this summer.

Outlook on the World’s Largest Thermal Energy Storage Plant by POET

The world’s largest thermal energy storage plant by POET is one that has already been hailed as a significant game changer. Officials said the new technology will be a major economic and environmental boost to South Dakota. It is also anticipated to pioneer the use of a new energy technology for potential use across the country and the world. “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,” said Jeff Lautt, president and chief operating officer of POET in Sioux Falls.

The firm is the world’s largest producer of ethanol. On the other hand, Senator John Thine noted the facility is a monumental step in advancing US’s economy. “Homegrown energy sources create good-paying jobs, support our agriculture producers, and provide affordable options for consumers. I’m grateful for this impressive addition to South Dakota’s budding biofuels industry, and I can’t wait to see the benefits for South Dakota producers and families across our state.”

Project Factsheet:

• Project Name: POET Thermal Energy Storage Project
• Location: Big Stone City, South Dakota, USA
• Estimated Investment Value: Not officially disclosed
• Project Type: Thermal Energy Storage / Industrial Clean Energy Infrastructure

Timeline

• 2025: Construction completed in under one year
• 2026: Plant launched and supplying power to adjacent ethanol facility
• Q4 2026: Expected full operational status by October

Site & Scale

• Storage Capacity: 5 Gigawatt-hours (GWh)
• Facility Status: World’s largest thermal energy storage plant
• Industrial Integration: Connected to POET ethanol production facility
• Ethanol Plant Capacity: Approximately 92 million gallons annually

Project Teams

• Industrial Partner: POET
• Technology Partner: Antora Energy
• Primary Investor: Grok Ventures
• Political Support: Bipartisan federal and state backing

Infrastructure Scope

• Large-scale thermal energy storage system
• Carbon block heat storage technology operating at up to 4,000°F
• Wind energy capture and storage infrastructure
• Also industrial energy integration with ethanol production operations
• Power delivery systems for adjacent biofuels facility

Strategic Objectives

• Capture excess wind energy that would otherwise be curtailed
• Reduce reliance on fossil fuels for industrial heat and power
• Also improve ethanol production efficiency
• Support South Dakota’s biofuels and agricultural sectors
• Expand markets for regional corn producers
• It also demonstrate scalable long-duration energy storage technology
• Advance U.S. clean energy and industrial decarbonization efforts

Challenges

• Scaling first-of-its-kind commercial thermal storage technology
• Managing ultra-high-temperature storage systems safely
• Also integrating intermittent renewable energy into industrial operations
• Ensuring long-term operational reliability and efficiency
• Also commercializing emerging energy storage technologies at large scale

Current Status

• Facility officially launched and operational
• Already supplying energy to POET’s ethanol production plant
• Final operational ramp-up also continuing toward full Q4 completion
• Antora Energy’s first commercial production-scale installation now active