Fourth Power secures $19M Series A funding on the back of three major breakthroughs.

Congratulations, we’ve achieved it! Solar and wind energy have become the most cost-effective sources of electricity in the United States. It might seem like we can now simply let the market take its course, but there’s more to the story.

While it’s true that solar and wind power are the cheapest when they are generating electricity, they are intermittent sources. Wind doesn’t blow consistently everywhere, and the sun sets daily. This necessitates finding methods to store the energy they produce.

Lithium-ion batteries have been the dominant solution, mainly due to their large-scale production, which has lowered their costs. These batteries are modular and quick to respond to demand, making them a flexible addition to the grid.

However, despite their advantages, lithium-ion batteries are not ideal for storing large amounts of energy cost-effectively. Over the past few years, researchers have been actively working on alternative solutions for large-scale energy storage.

Asegun Henry, an MIT professor, has been exploring an alternative approach for quite some time. Originally, he wasn’t trying to compete with lithium-ion batteries but was focused on finding ways to harness solar energy and transport it as heat at higher temperatures and efficiency.

This journey led to the creation of Fourth Power, a company founded by Henry last year. Fourth Power’s innovation involves a thermal battery that stores energy using graphite blocks at temperatures around 2,400°C (4,350°F). These blocks are charged by molten tin, heated using electricity from solar panels or wind turbines. When it’s time to release the stored energy, the tin absorbs heat from the graphite blocks and transfers it through carbon stacks until they become white hot. Specially designed photovoltaic panels tuned to infrared light then absorb this thermal energy.

The entire system is designed to operate in an oxygen-free environment to prevent corrosion and is well-insulated to minimize energy loss, losing only about 1% of energy per day.

Fourth Power’s thermal battery is built on three critical breakthroughs, all stemming from Henry’s work at MIT. These include a robust graphite-based pumping and plumbing system capable of withstanding extreme temperatures, highly efficient thermal photovoltaic cells, and a method to maintain the cleanliness of PV cells in the presence of superheated materials.

Henry chose thermal photovoltaic technology over traditional steam turbines due to its ability to handle high temperatures, faster response times, and lower costs for proving scalability. He believes there is potential to further enhance the efficiency of solar panels used in this system.

Fourth Power’s technology could also be applied to provide industrial heat, although this is a future possibility, as industrial installations require customized engineering solutions.

The company was established to move beyond laboratory experiments and gather extensive data in an industrial context. Funding for this endeavor came through a $19 million Series A round, led by DCVC, with participation from Breakthrough Energy Ventures and the Black Venture Capital Consortium.

Fourth Power aims to have a 1-megawatt-hour pilot system operational within two years at MIT’s Bates Lab near Boston. With cost estimates targeting $25 per kilowatt-hour, significantly cheaper than lithium-ion batteries and competitive with other long-duration storage technologies, Fourth Power is well-positioned in the growing energy storage market, which is expected to double by the end of the decade, according to BloombergNEF.

For Fourth Power, the focus is not just about outcompeting rivals but also about constructing a commercial-scale plant capable of storing 1 gigawatt-hour of electricity, where the economics could be highly favorable for both the company and its investors.