Fourth Power Raises $20M Series A Plus for Thermal Battery Tech

Fourth Power, a Cambridge, Massachusetts-based startup, secured $20 million in a Series A Plus funding round. Munich Re Ventures led this Fourth Power funding. This capital will advance the company's innovative thermal battery technology.

The four-year-old company develops thermal batteries designed for long-duration energy storage. These systems use superheated liquid tin and argon-filled chambers. Electricity heats carbon blocks, and then thermophotovoltaic cells convert the heat back into power. This technology aims to provide continuous, cost-effective electricity from renewable energy sources.

Fourth Power plans to deliver commercial-scale batteries by 2028. The company is currently designing a 1-megawatt-hour demonstration battery. This new Fourth Power funding supports building its first full-scale battery. The technology projects costs significantly below lithium-ion batteries and natural-gas peaking plants.

Advancing Thermal Battery Deployment

The thermal batteries offer over eight hours of continuous electricity, double the duration of most grid-scale battery storage solutions. Fourth Power targets a storage cost of $25 per kilowatt-hour at large scale. This represents one-tenth the cost of current lithium-ion alternatives and aims to compete with solutions from companies like Form Energy. The system maintains stable temperatures, losing only 1% of stored energy daily.

Breakthrough Energy Ventures and DCVC also participated in the Series A Plus round. Fourth Power previously raised a $19 million Series A in 2023. This latest Fourth Power funding accelerates its path to market.