The renewable energy transition in the U.S. is accelerating, and Fourth Power, a startup, has secured $20 million to develop a new thermal energy storage system. This system aims to address the need for long-duration energy storage that is both affordable and scalable, potentially transforming the energy landscape beyond dependence on fossil fuels. It utilizes melted tin for heat transfer, making it significantly cheaper than traditional lithium-ion batteries. With this funding, Fourth Power plans to advance its testing and move toward commercial applications, showcasing the innovation driving the future of clean energy.
US presidents come and go, but the renewable energy transition is permanent and inevitable. Also, follow the money. Despite the abrupt shift in federal energy policy this year, investors are still banking on next-generation solutions to the climate crisis. Exhibit A is the US startup Fourth Power, which has just nailed down $20 million to bring its new thermal energy storage system to market. A new, extra-cheap energy storage system will help kickstart the US energy transition back into high gear if and when (spoiler alert: when) the current occupant of the White House leaves office as scheduled on January 20, 2029. For that matter, the only two energy storage systems in widespread use today are the same ones that existed during the renewables-friendly administrations of former Presidents Obama and Biden, but we need more of the kind of long-duration, inexpensive systems that are needed to smooth out the bumps in a grid fully saturated with wind, solar, and other renewable energy resources.
One of those two types currently in widespread use is pumped hydropower. The basic technology has been in use for over a century and it currently accounts for about 95% of long-duration energy storage in the US. There are some opportunities for expansion in the coming years, but scope of the field is limited by the availability of suitable elevation and water resources, among other obstacles. New types of pumped storage are in development, but similar limitations apply. Lithium-ion battery arrays are the other form of energy storage. Utility-scale battery systems have a much more flexible scope of application, but they don’t deliver on the long-duration side. They can hold onto energy for a handful of hours, which is enough to handle routine daily grid tasks and the occasional emergency. However, the US Department of Energy (such as it is today) has been on the prowl for systems that last at least 10 hours, on up through multiple days, weeks, and even seasons, to complement a longstanding grid modernization program that calls for more renewable energy and more decentralized, distributed energy resources.
Fourth Power sailed across the CleanTechnica radar back in 2023, when it raised $19 million in Series A funding to support the development of a 1 megawatt-e prototype thermal energy storage system. The eye-catching goal was to become 10 times cheaper than conventional lithium-ion batteries, due in large part to supply chain savings. The lost cost of materials is typical of thermal storage systems, which collect heat in the form of sunlight or an electrical current supplied by renewable resources. Fourth Power has added a twist of its own, using melted tin as a transfer medium that shunts electricity-sourced heat into carbon blocks for storage. To discharge the blocks, Fourth Power applies a proprietary system that transfers heat back into electricity. “The company’s use of very high-temperature liquid metal for heat transfer achieves unprecedented power density, dramatically reducing overall system costs,” Fourth Power explains.
The ability to cut down on commercial-scale manufacturing costs remains to be seen, but two years ago, Fourth Power was confident that the materials alone would make the difference. “By using readily available and less expensive materials, the overall system cost is lower, enabling energy storage that is ten times cheaper than lithium-ion batteries,” Fourth Wall stated in a press release in December of 2023, referring to its low cost tin-and-carbon formula. Fourth Power is still confident. The system was still undergoing additional testing back in 2023, but with