Boston, MA - Sep 16, 2025 (UTC) - Fourth Power, a flexible-duration energy storage provider, has secured $20 million in Series A Plus funding to accelerate the commercial deployment of its modular, utility-scale thermal energy storage system. The investment round was led by Munich Re Ventures, with follow-on investments from DCVC and Breakthrough Energy Ventures, bringing the company’s total funding to $40 million.
The funding will support commissioning of the company’s 1 MWh-e demonstration facility outside Boston and build out sales and partnerships pipeline as utilities face surging demand from electrification and artificial intelligence advancement. Fourth Power has built a battery that can transform electricity into heat, store it in carbon blocks that get hot enough to glow, and later convert that heat back to electricity when needed.
The company’s thermal battery technology uses renewable energy to heat carbon blocks to temperatures so hot they glow like the sun, storing energy for both short- and long-term durations before releasing it back to the grid as electricity. The system heats liquid tin and moves it through a piping system to heat stacks of carbon blocks until they glow white hot, then uses thermophotovoltaic cells to convert the light into electricity.
“Our vision has always been to tackle climate change by making renewable energy – which is the most cost-effective form of power – a reliable resource for the grid to use at all hours of the day,” said Arvin Ganesan, CEO of Fourth Power. “We need utility-scale energy storage that can grow with the grid to make this a reality on a global scale. With the support of our investors, Fourth Power will accelerate our mission and reshape the clean energy landscape by making grid-scale thermal battery storage the most cost-effective solution for power production.”
“Fourth’s Power’s solution is an engineered sun-in-a-box,” said Zachary Bogue, co-founder and managing partner at DCVC. “We are thrilled to join forces with this exceptional team, whose best-in-class technology can greatly increase the production and use of renewable energy.”
Fourth Power’s approach offers grid operators control and flexibility at lower cost compared to other energy storage options, with the capability to store renewable energy that would otherwise be wasted due to curtailment for over a month. The modular and scalable system can meet today’s short-duration needs and future longer-duration requirements while maintaining the ability to discharge within seconds.
“Clean energy storage that is reliable and scalable will be a cornerstone of a zero-carbon future,” said Carmichael Roberts of Breakthrough Energy Ventures. “Fourth Power’s years of research and technological breakthroughs leave them well-positioned to accelerate the development of its innovative storage solutions and achieve significant milestones in the coming years.”
The technology, developed by founder and CTO Asegun Henry when he was a professor at Georgia Tech and now at MIT, holds several records including the Guinness World Record for the highest temperature pumping of liquid metal at 1200°C degrees and thermophotovoltaic efficiency at 41%.
“After more than ten years of research and development, we are grateful to reach this crucial milestone in our journey thanks to our funding partners who recognized the innovation and potential of Fourth Power’s thermal battery technology,” said Henry. “I’m proud to lead this team of engineering experts and look forward to continuing our work to develop a long-duration energy storage solution that can be significantly cheaper than existing solutions, reliable, and, importantly, scalable without the necessity of mining for lithium.”
About Fourth Power
Backed by more than a decade of R&D, Fourth Power provides utility-scale thermal battery solutions that store renewable energy as heat for short and long durations to dispatch electricity to the grid in seconds. Developed by MIT and Georgia Tech scholars, the company aims to supply affordable and reliable clean power using innovative thermal technology with thermophotovoltaic solar cells, turning the light from heated carbon blocks into electricity. The company holds several records, including the record for thermophotovoltaic efficiency at 41% and a Guinness World Record for the highest temperature pump at 1200°C degrees. Fourth Power’s extremely high temperature system ensures maximum efficiency with readily available materials, making its technology the lowest-cost option for grid decarbonization.
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Technica Communications
Melanie Morris
fourthpower@technica.inc
