Fourth Power’s sci-fi thermal batteries could be cheaper than pricey natural gas power plants

Fourth Power is making waves in the energy sector with its groundbreaking approach to long-duration energy storage, reminiscent of high-tech innovations in sci-fi cinema. The company is developing thermal batteries that utilize superheated liquid tin within hermetically sealed chambers filled with argon, with the aim of providing affordable electricity storage that promotes the adoption of solar and wind energy for round-the-clock power supply. The technology leverages electricity from the grid to heat carbon blocks inside insulated chambers, which are then filled with argon gas. When energy demand spikes, the system channels molten tin—heated to an astonishing 2,400°C (4,352°F)—through specially designed graphite pipes that endure such extreme temperatures. This superheated tin emits infrared light, which is captured by thermophotovoltaic cells that convert it back into electricity. Having spent the past two years refining this innovative technology, the startup based in Cambridge, Massachusetts, is gearing up to construct its first full-scale thermal battery. By 2028, Fourth Power aims to deliver commercially viable batteries at a price point that could significantly undercut both lithium-ion batteries and traditional natural gas peaking plants. Co-founder and CEO Arvin Ganesan expressed confidence in their projections, stating, "Our first-of-a-kind products will be cost competitive in the market." Designed for daily charging and discharging, Fourth Power's batteries are projected to provide continuous power for approximately eight hours, which is notably longer than the typical duration of most grid-scale lithium-ion batteries. Their insulation system, crafted from petroleum coke—a byproduct of oil refining—ensures stable temperatures, with only a 1% energy loss per day. Currently, the company is conducting rigorous tests on smaller prototypes to validate performance and durability. Alongside these efforts, they are also working on a 1-megawatt-hour demonstration battery. To support this initiative, Fourth Power has successfully raised $20 million in a Series A Plus funding round led by Munich Re Ventures, with additional contributions from Breakthrough Energy Ventures and DCVC. This follows a previous $19 million Series A round in 2023. Ultimately, Fourth Power has ambitious plans for large-scale production, aiming to reduce the cost of electricity storage using its thermal batteries to just $25 per kilowatt-hour—one-tenth the expense of lithium-ion batteries. Ganesan remarked, "With fewer moving parts and players in the supply chain, we believe reaching our $25 target is quite feasible."