Firebrick thermal battery reaches 20 MWh commercial scale

At the Southwest Research Institute in San Antonio, Texas, a stack of firebricks is now doing a job usually assigned to fossil fuels: holding heat for industry. Electrified Thermal Solutions commissioned its first 20 MWh commercial-scale system earlier this year, bringing its Joule Hive Thermal Battery, also known as the E-brick, out of the laboratory and into a working site.

The Boston-based startup is targeting factories that need very hot process heat, including steel, cement and chemical plants. The E-brick combines conventional firebricks with advanced firebricks that conduct electricity. Those bricks serve three roles at once: heating elements, thermal storage media and heat exchangers. Electricity is stored as heat during off-peak periods, then released as hot air through channels in the bricks to furnaces, kilns or boilers.

The temperature range is industrial rather than domestic. Electrified Thermal Solutions says the system can store heat at up to 1,800 C, with output adjustable from 200 C to 1,800 C. It is compatible with electrical supplies ranging from 480 V to 100 kV. The company also says it converts and stores power as heat at greater than 98% efficiency.

The practical payoff is flexibility for both factories and grids. A plant could charge the battery when electricity is cheap, including the negative-price hours the company says it targets in Texas, then draw on stored heat when production requires it. Electrified Thermal Solutions says pairing the system with on-site solar could let a factory oversize its solar installation relative to its grid connection and turn midday surplus into firm, around-the-clock industrial heat.

The limits are equally concrete: this is the company's first commercial-scale installation, not evidence of broad deployment. Its economics depend heavily on the charging electricity price. CEO and co-founder Daniel Stack says the system can beat natural gas, without subsidies, where delivered prices exceed €30 ($34.8)/MWh. Founded in 2022, the startup has raised $24.3 million across six funding rounds.