$19 million investment for molten tin thermal energy storage technology
Backed by Bill Gates’ venture firm Breakthrough Energy Ventures, Fourth Power has received $19 million in funding for its molten tin high-density thermal energy storage (TES) system based on thermophotovoltaic (TPV) cells, reportedly at a cost ten times cheaper than lithium-ion batteries.
The investment round was led by venture capital firm DCVC, with participation from Breakthrough Energy Ventures and Black Venture Capital Consortium. The funding will be used to construct a 1 MWh prototype, targeted for completion in 2026, and for additional testing and the expansion of the company’s engineering team.
Discussing the project’s future, Asegun Henry, founder and Chief Technical Officer at Fourth Power commented, “Following the 1 MWh prototype facility’s successful completion, we plan to partner with utilities to conduct pilot projects designed for commercialization throughout 2026 and 2027… We anticipate achieving our goal of installing full-scale, 100 MWh systems by 2028”.
In Fourth Power’s patented liquid metal heat transfer process, molten tin is applied to graphite blocks, and light emitted from the superheated graphite is reflected onto TPV cells, which convert (traditionally, solar) heat to electricity. This system is sealed within an argon gas-filled warehouse to stabilize the system for safety and efficiency.
Tin is an excellent heat transfer fluid due to its properties including low viscosity, high thermal diffusivity, and a wide range between its melting and boiling points (232 C – 2600 C).
Fourth Power’s technology currently yields an efficiency of 41%, the highest for TPV cells, and the company “[has] designs to reach 50%”, according to Henry. Continuing, Henry commented, “The key is our liquid metal handling infrastructure, which allows us to transfer heat at fluxes more than an order of magnitude higher than traditional thermofluid systems… [leading] to higher power density and lower cost.”
Scalability has been a key obstacle for Fourth Power and its competitors to overcome, but the company has stated its technology is modular and can be scaled further. We look forward to announcements on the development of the pilot project. Significant investment into new tin technologies highlights the future of continued long-term tin demand growth.
