Fourth Power Develops Thermal Battery Storing Heat at 4,350°F for Up to 100 Hours

Fourth Power has developed a thermal battery that stores electricity as heat in carbon blocks heated to 4,350°F, capable of providing power for 10 to over 100 hours at a lower cost than lithium-ion batteries. Founded by MIT professor Asegun Henry, the system uses molten tin for heat transfer and captures emitted light with thermophotovoltaic cells to generate electricity. This innovation builds on Henry's prior work, which set a Guinness World Record for the hottest liquid pump.

Published Mar 21, 2026

Fourth Power's new thermal battery stores electricity as heat in carbon blocks heated to 4,350°F (2,400°C). Founded by MIT professor Asegun Henry, the system can provide power for 10 to over 100 hours at a lower cost than lithium-ion batteries.

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The design employs molten tin to transfer heat, presenting a potential alternative for long-duration storage. At peak charge, the carbon blocks glow white-hot, emitting light that is captured by thermophotovoltaic cells to generate electricity. This innovative approach builds on Henry's previous work that earned a Guinness World Record for the hottest liquid pump.