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Fourth Power raises $19M for thermal batteries

Illustration of a dollar sign made out of metal, and glowing very bright.

Illustration: Allie Carl/Axios

Thermal energy storage developer Fourth Power closed a $19 million Series A to develop large battery systems for electric grids, the startup tells Axios.

Why it matters: The company says its batteries can provide as much energy as conventional lithium-ion batteries at a tenth of the cost and for as long as four days.

Catch up fast: Thermal energy storage uses extreme heat to store electricity.

  • The tech can use a variety of common materials, making it cheaper than conventional electrochemical batteries that use minerals like lithium.
  • The downside is that thermal systems have tended to be less efficient, making them suitable for fewer roles.

The latest: Fourth Power says it has designed a thermal energy system using graphite that can reach much higher temperatures than previous thermal designs — producing energy density that's comparable to lithium-ion at a fraction of the cost.

  • The design effectively allows molten tin to flow at 2,000 degrees Celsius, an innovation that set a Guinness World Record.

Between the lines: The tech is somewhat material agnostic. So while China in October restricted its graphite exports, "our trajectory is to look at being able to utilize a variety of sources of carbon as a starting point," CTO Asegun Henry tells Axios.

Details: DCVC led the all-equity round, which closed in November.

  • Breakthrough Energy Ventures and the Black Venture Capital Consortium joined.
  • DCVC partner Rachel Slaybaugh, Breakthrough Energy Ventures managing partner Phil Larochelle, investor Jason Hartlove, a VP at Meta, and CEO Arvin Ganesan joined Fourth Power's board.

Of note: Ganesan was named CEO in June. He was previously head of global energy and environment policy at Apple.

What's next: Fourth Power, based in Boston, plans to build a 1 MWh demonstration at an MIT site north of the city. It's for now targeting the utility-scale storage market, but keeping an eye toward other opportunities, such as industrial heat.

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