Fourth Power recently received $19 million in Series A funding to scale its cost-effective thermal battery technology. The investment round was led by the venture capital firm DCVC, with participation from Breakthrough Energy Ventures (BEV) and Black Venture Capital Consortium. In addition to helping scale the company’s thermal energy storage solution, which can store energy for both short- and long-term durations to be put back on the grid as electricity, the investment will initiate the construction of a 1 MWh-e prototype facility outside Boston, with a 2026 anticipated completion date.

Fourth Power said its technology uses renewable energy to heat carbon blocks to temperatures so hot they glow like the sun and later release that heat on demand to the grid as electricity. Fourth Power’s system converts renewable energy to heat, or thermal energy, which can be stored until needed. The thermal battery heats liquid tin and moves it through a piping system to heat stacks of carbon blocks until they glow white hot. The system then exposes thermophotovoltaic (TPV) cells to the light and converts it into electricity. The solution is designed to maximize the value of renewable energy generation and offer grid operators control and flexibility at the lowest cost compared to other energy storage options. The system is also modular and scalable by adding more carbon blocks to increase storage duration, allowing growth with the grid as renewable generation increases.

Fourth Power said its approach to utility-scale energy storage considers the expected growth of wind and solar generation. With Fourth Power’s solution, the company said renewable energy that would otherwise be wasted due to curtailment can be stored for over a month and discharged over any period from a few hours to a few days while maintaining the lowest possible cost.

Beyond the development of its initial 1 MWh-e facility, Fourth Power said the funding will facilitate rigorous durability tests and expand the company’s engineering team to meet the market’s growing demands.