Sunnyvale Tech Powers Wind Storage Scale

Antora Energy’s thermophotovoltaic work in Sunnyvale has moved from pilot manufacturing into a first large commercial deployment in the Midwest. On May 19, Antora and biofuels producer POET said they commissioned a 5-gigawatt-hour thermal energy storage system at POET’s bioprocessing site in Big Stone City, South Dakota. The project uses Antora’s thermal batteries to absorb low-cost electricity, including surplus wind power, and store it as heat in blocks of carbon. Antora says the same platform can later deliver industrial heat directly or convert stored heat back into electricity through thermophotovoltaic, or TPV, cells. ### How does the Sunnyvale technology fit into the South Dakota project? Sunnyvale, California is where Antora built what it described in January 2023 as the world’s first dedicated manufacturing line for TPV cells. The company said that line had an initial capacity of 2 megawatts of TPV cells a year and was designed to turn a lab technology into a manufacturable product. Antora said in October 2023 that the Sunnyvale TPV facility would supply the heat-to-power component for future thermal battery products, while large-scale battery module manufacturing would take place in San Jose. That split matters because the Big Stone City system is built around thermal batteries made in California, while the TPV program is the part intended to let stored heat be discharged as electricity as well as heat. ### What exactly is Antora storing, and in what form? Antora says its batteries store renewable electricity as heat in solid carbon blocks. The company has described carbon as an abundant storage medium and says the modules also include insulation, enclosures, charging equipment and discharge equipment. Big Stone City’s system is designed to soak up electricity that might otherwise be curtailed. South Dakota News Watch reported that the project will absorb excess wind energy that cannot always find room on the grid and hold it for later use at the ethanol plant. Jeff Lautt, POET’s president and chief operating officer, told the outlet the system is capturing wind power that “otherwise would be wasted.” ### Where do thermophotovoltaic cells come in? Antora said in November 2023 that TPV cells are the component that converts stored heat back into electricity. The company said conventional heat engines such as steam turbines have faced limits on cost, complexity and scalability in similar applications, and it argued that TPV offers a way to provide power output with no moving parts. The company said it had demonstrated heat-to-electricity conversion efficiency above 40% and received more than $4 million in California Energy Commission and ARPA-E funding to expand TPV production. ARPA-E has separately described Antora’s system as converting intermittent renewable energy, including wind and solar, into industrial heat and power through TPV technology. ### Why is the first big deployment at an ethanol plant in South Dakota? POET said on May 19 that the Big Stone City project gives its plant around-the-clock energy under a long-term heat offtake agreement. The company said that should improve efficiency and lower costs at the site, which produces bioethanol. Big Stone City is also in a region with strong wind generation. Antora and POET said the project advanced from initial construction to delivering energy in under 12 months, and South Dakota News Watch reported that company executives see the system as a way to use surplus wind power while reducing reliance on fossil fuels at the plant. ### Is this a pilot, or is it already commercial scale? The South Dakota project is beyond a lab or factory pilot. POET and Antora said the system has 5 gigawatt-hours of storage capacity and includes more than 200 thermal batteries, putting it among the world’s largest energy storage projects by capacity once fully completed. The manufacturing build-out is still staged. Antora’s TPV line in Sunnyvale began as a pilot-scale production line, while its 50,000-square-foot San Jose facility was announced in 2023 as the company’s first large-scale thermal battery factory. Antora said that plant’s initial units would roll off the line in 2024 and that additional, larger manufacturing sites are planned. ### What happens next? May 19 is the key date for the current milestone: commissioning at POET’s Big Stone City facility. Antora and POET said the South Dakota system will be fully operational later in 2026, and Antora has said it is developing additional projects across the country, including with ethanol producers in the Midwest.