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

Fourth Power is advancing a novel long-duration thermal energy storage system, utilizing superheated liquid tin and thermophotovoltaic cells, designed to provide 24/7 renewable power at costs projected to undercut lithium-ion batteries and natural gas peaker plants. The company, which recently raised $20 million in a Series A Plus round led by Munich Re Ventures, aims for commercial-scale deployment by 2028, targeting a storage cost of $25/kWh and offering over eight hours of continuous discharge, potentially transforming grid-scale energy storage.

Analysis

Fourth Power, a four-year-old startup, is advancing a novel long-duration thermal energy storage technology with the potential to significantly disrupt the grid-scale market. The company recently secured $20 million in a Series A Plus funding round led by Munich Re Ventures, with participation from notable investors like Breakthrough Energy Ventures and DCVC, bringing its total raised since 2023 to $39 million. This new capital is earmarked for building a 1-megawatt-hour demonstration battery. The technology utilizes superheated liquid tin at 2,400°C and thermophotovoltaic cells to convert heat back to electricity, aiming to provide continuous power for eight hours or more—double the duration of most commercial lithium-ion systems—with an energy loss of only 1% per day. The CEO, Arvin Ganesan, projects that initial commercial units, slated for delivery by 2028, will be cost-competitive with natural gas peaker plants and that scaled production could achieve a storage cost of $25 per kilowatt-hour, a tenfold reduction compared to current lithium-ion batteries. While the technology presents significant engineering challenges due to its extreme operating temperatures, its reliance on a simplified supply chain of carbon, tin, and petroleum coke could insulate it from the price volatility of battery metals like lithium and cobalt.

Key Decisions for Investors

• Private market investors should view Fourth Power as a high-risk, high-reward opportunity in the energy transition space, where the credibility of its backers like Breakthrough Energy Ventures is weighed against the significant technical hurdles of scaling a 2,400°C thermal system.
• Investors with long-term positions in utilities, renewable energy developers, and lithium-ion battery supply chains should monitor the company's progress on its 1-MWh demonstration project, as achieving its targeted $25/kWh cost by 2028 would represent a major deflationary and disruptive force in grid storage.
• Given the early stage of development, it is prudent to track the results of the company's ongoing durability and power output cycle tests before factoring its technology into long-term financial models for the energy sector.
• Consider the potential long-term impact on commodity markets; if successful, this technology could reduce future demand growth for lithium and cobalt while increasing demand for industrial graphite, tin, and petroleum coke for grid-scale applications.