Antora Energy — Startup Profile

The thermal-battery company storing renewable power in glowing-hot carbon blocks to run industry and data centers around the clock

HQ: San Jose, CA, USA (North San Jose Zanker Road manufacturing campus; Sunnyvale registered address and office; earlier HQ in Sunnyvale) | Founded: 2018 | Employees: ~270–310 (LinkedIn ~272; PitchBook ~277; Revelio Labs ~308 as of March 2026) | Stage: Series C (Private) | Website: https://antoraenergy.com (301-redirects to https://antora.com)

About

Antora Energy builds factory-made thermal batteries that store low-cost renewable electricity as heat in insulated blocks of solid carbon, then deliver that energy around the clock as industrial process heat or firm electricity. The company was founded in 2018 by Andrew Ponec (CEO, previously founded Dragonfly Systems, acquired by SunPower in 2014), Justin Briggs (COO, Stanford applied physics PhD), and David Bierman (CCO, MIT mechanical engineering PhD, founder of Marigold Power), who merged their efforts after meeting through the Cyclotron Road incubator and the Activate Fellowship.

Technically, the system resistively heats carbon blocks — earth-abundant, with no thermal-runaway risk — to temperatures up to 2,400°C, far above molten-salt systems. Heat discharges directly to industrial processes; electricity is generated today via off-the-shelf steam turbines paired with the storage, with Antora's in-house thermophotovoltaic (TPV) cells (>40% efficiency demonstrated, world's first dedicated TPV line) positioned as a future conversion product. Batteries are made at the expanded San Jose, California gigafactory.

The commercial milestone is Project Big Stone: a 5 GWh, 50 MW system commissioned in May 2026 at POET's plant in Big Stone City, South Dakota — over 200 batteries, empty lot to energy delivery in under 12 months, among the largest battery storage projects in the world, under a long-term heat offtake with zero offtaker capex. Antora has raised roughly $770M in equity since inception, including a $550M Series C in July 2026 co-led by G2 Venture Partners and Eclipse, plus ARPA-E and DOE awards. The company employs roughly 270–310 people and is establishing a second U.S. manufacturing hub while pursuing signed (unnamed) hyperscaler data-center agreements.

The Take

Antora's bet is that the cheapest path to round-the-clock industrial energy is not better lithium batteries or green hydrogen, but heat itself: charge insulated blocks of solid carbon with the cheapest hours of wind and solar, store the energy at up to 2,400°C, and discharge it as industrial heat or firm electricity. Carbon is abundant (the company notes it is the fourth-most-produced industrial material on Earth), roughly a tenth the cost of lithium-ion battery materials, free of critical-mineral supply risk, and stable for 20+ years without cycling degradation — a deliberately unsexy materials choice that lets Antora manufacture road-shippable modules on ordinary supply chains.

The company proved the concept with a commercial-scale system at Wellhead Electric near Fresno in September 2023, opened its San Jose factory a month later, raised a $150M Series B led by Decarbonization Partners (BlackRock/Temasek) in February 2024, and delivered its proof point in May 2026: Project Big Stone, a 5 GWh, 50 MW multi-day thermal battery at POET's ethanol plant in Big Stone City, South Dakota — over 200 modules, empty lot to energy delivery in under 12 months, among the largest battery storage systems in the world, under a long-term heat offtake with zero offtaker capex.

That deployment also marks the strategic pivot. Antora now sells firm power to data centers and the grid as aggressively as industrial heat; its $550M Series C (July 2026, co-led by G2 Venture Partners and Eclipse) cites signed hyperscaler agreements — though names, binding status, capacity and timing are undisclosed. Commercial power today flows through off-the-shelf steam turbines; the higher-efficiency TPV heat-to-power path remains a future product. The open questions are executional: whether steam-turbine economics win data-center deals against lithium-ion, whether tariff structures like Otter Tail Power's replicate, and whether the undisclosed pipeline converts into steel in the ground.

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